The Linux Gazette Mailbag
Apache Server Question
(marnie.mclaughlin at gmail.com) marnie.mclaughlin at gmail.com
Sat May 13 09:17:24 PDT 2006
Answered by: Ben
[ This one slipped through without an answer - anyone out there have a suggestion for Marnie? -- Kat ]
[Ben] - This is from a friend of mine; my memory of how to do this is rather
fuzzy, so I'm hoping that someone here will have a bit more recent Apache experience
than I do.
Hi Ben,
I have a Linux question for you if you don't mind:)
My boyfriend is a Linux Admin and wants to display a different directory
per user based on _SERVER{PHP_AUTH_USER}
For example:
http://server/home/
should point to http://server/home/user1/ or
should point to http://server/home/user2/
Both directories should appear to be the same (i.e. /home/) home could
be a PHP script or anything else that will work:)
What would you suggest or where can I look for help?
Fank you:)
Marnie
OSS external midi plays to AWE
sindi keesan (keesan at sdf.lonestar.org)
Fri May 12 18:33:24 PDT 2006
Answered by:
[ No one has had an answered for this one yet. Maybe there's
someone reading this issue of LG who does? -- Kat ]
I checked your knowledge base and found my own posting from 2005. The
MIDI howto is for ALSA and I am using 2.2.16 kernel and OSS.
Last year you helped me to play AWE files in linux, using my abbreviated
version of Slackware 7.1 (I had compiled playmidi and drvmidi but I needed sfxload
and a sound bank). I now know how to play FM synthesis and AWE midi in DOS and
linux, after setting the sound card in DOS with ctcm and loading soundbank with
sfxload. drvmidi or playmidi -a does AWE, playmidi -4 or -f does FM synthesis,
and playmidi -e is supposed to play to the external midi device but it DOES
NOT.
I also have the file I was missing that was needed to convert rpm to
tgz so I can use precompiled rpm packages (rpm2cpio as used by rpm2targz).
If I have inserted awe_wave.o, playmidi -e plays AWE not external,
and if I have not inserted it I get an error message about /dev/sequencer not
found and device or resource being busy.
cat /dev/sndstat does not do anything (some error message about the
device not existing). cat file.midi > /dev/sequencer says the device does
not exist or is busy or something.
I have made /dev/sequencer and /dev/midi00 with symlink to /dev/midi
and /dev/dsp and /dev/audio and /dev/music and /dev/sndstat.
In DOS I run ctcm to set the addresses and irqs, after which the pnp
AWE cards work properly in DOS, then I boot with loadlin into linux and the
settings are retained and I can play to external MIDI with several DOS programs,
or AWE or FM synthesis.
Soundblaster AWE64 card (ISA, pnp)
Using a 2.2.16 kernel which I compiled with support for sound:
insmod soundcore
insmod soundlow
insmod sound
insmod v_midi (Do I need this one? Is it causing problems?)
insmod uart401
(Sometimes also insmod mpu401, makes no difference)
insmod sb io=0x220 mpu_io=0x330 irq=5 dma=1 dma16=5
insmod awe_wave (for AWE sound only)
sfxload /usr/lib/sfbank/synthgm.sbk (the sound bank)
insmod opl3 io=0x388 (for FM synthesis only)
Or with a 2.4.31 kernel
insmod soundcore
insmod sb_lib
insmod sb.....
Do I need support for joystick or gameport as well? My kernel has modular
support for joystick but I don't have a joystick.
The only info I could find online was requests from other people who
had their external midi devices working in Win95 not in linux. With playmidi
-e or Rosegarden they either did not play, or played as FM synthesis on a card
without AWE. Mine plays as AWE, perhaps because I set that as the playmidi default.
External midi works in DOS with several programs such as playb.exe
(playpak) and beatmaster. We have an OEM midi cable and a Yamaha Clavinova with
the cable plugged in properly (OUT of cable to IN of piano and vice versa -
no sound came through when we plugged it backwards). The joystick port is not
disabled on the card in ctcm, and I tried a non-AWE card too with jumper set
to joystick enabled.
I also tried the basic (bare.i) kernels from Slackware 7.1 and 10.2
and I think 8.1 (one of them would not even play AWE sound). They all seem to
have full sound support, mostly as modules.
What little step might I have left out, or is there a bug in playmidi?
You helped me back in around 2002 to set up a 2MB ramdisk linux with
mdacon (to use both TTL and VGA monitors) and tried to teach me how to use screen
and suid. I still do not have modprobe, just insmod.
Proofing C
The Answer Gang (tag at linuxgazette.net)
Wed Apr 5 14:03:27 PDT 2006
Answered by: Ben, Jason, Neil
[ This was originally part of the Talkback:
122/sreejith.html discussion. -- Kat ]
[Jason] - [ Aside to the Answer Gang: I am by no means a C expert, but I know
a little bit about the language. ISTR some reader volunteering to proofread
C code that comes up in future articles, but if not, I could step in and try
to catch the obvious technical stuff.]
[[Ben]] - Well, Jan-Benedict Glaw volunteered - but I haven't actually seen
any result from it, despite prodding him a couple of times. I guess he's been
busy, or something. Your offer is gratefully accepted, since my C is too rusty
to be useful except in trivial cases.
[[[Neil]]] - Feel free to CC me for a second opinion on any C/C++ stuff.
[[[[Ben]]]] - That's great, Neil; accepted with thanks. Even with Jason's kind offer,
it would still be very nice to have more than one person available to do this.
Side note: anyone who contributes to the proofing process - technical, HTML
vetting, whatever - please add your name to that issue's STATUS file as described
there. We do not yet have a mechanism for using this, but at some point in
the near future, I'm hoping to have a bit of processing added that will display
those names on the index page of each issue. Either via my ham-handed efforts,
or someone else's Python skills (which would be greatly preferred; when I
take an axe to Python, it ain't pretty), but it will happen.
An idea
Benjamin A. Okopnik (ben at linuxgazette.net)
Wed Apr 19 18:23:07 PDT 2006
Answered by: Ben, Pablo, Thomas
[ cc'd to The Answer Gang for comments and further suggestions ]
On Wed, Apr 19, 2006 at 05:49:17PM -0700, Pablo Jadzinsky wrote:
> Dear editor,
>
> I am somewhat newbie to linux and I find your magazine the best
> resource I found so far. Even though I have great pleasure reading it
> and I find it extremely useful I have a suggestion.
> I think it would be great to have a 'homework' forum where every
> month a script or task can be suggested and then we (the readers)
> work on in during say 2 weeks. Some of us can send solutions to you
> and then someone on your team can post some of the different
> solutions with perhaps some comments on the different approaches. My
> experience says that the only way of really learning linux is through
> practice but at the beginning is difficult to use the system altogether.
>
> Any way, I hope you find my comment appropriate and useful.
>
> Thanks a lot
> Pablo Jadzinsky
Pablo, that's an excellent idea. I like it a lot; in fact, this is
one of the things I tried to do when I wrote the "Learning Perl" series
here a while ago. In fact, your idea gives me an idea:
How would you like to write this column?
Before you start objecting due to the fact that you're a "newbie"
[1], consider these two facts:
1) You don't have to come up with an answer to them yourself (although
I certainly hope that you'll try); posting them to The Answer Gang should get
a nice variety of answers which you could collate and use as part of next month's
article.
2) I suspect that most of us (it is certainly true for me) have by
now forgotten the specific kinds of problems that new users face, and would
have a tough time coming up with a list of them that would be relevant. You,
on the other hand, have the advantage of your position as a new user, and can
simply use any problems that you run into (after considering if they are of
general interest, of course.)
Besides... I don't like to mention it, because it's sort of like twisting
people's arms... but think of the *fame*. I mean, just imagine - "Pablo
Jadzinsky, Linux Gazette columnist." In *bold*, even. Women will swoon,
men will grit their teeth in envy, little green creatures from Beta Aurigae
will finally make contact with us because we've shown ourselves to be so highly
evolved... it's a winning scenario all around. Really. :)
[1] To quote Tom Christiansen, whose opinion, I fully share,
I find "Newbie" to be a grating, overly-cutsie buzzword
(read: obsequious neologism) used by people who are either
trying to be overly-cutsie or else who don't know that
"neophyte", "beginner" or "I'm new to" work just fine.
It sounds like something you'd be likely to find
in that offensively entitled line of books called
"XXX for Dummies".
[[Thomas]] - Been done before via various means --- some people (including myself)
tried setting various exercises in articles. But then this is only targetting
a specific audience: the people reading that specific article. (Ben's Perl series
at least had some reader feedback in this way).
[[[Ben]]] - Speaking of titles - "Thomas Adam, Linux Gazette cynic-in-residence."
Think of the fame, the... oh, right. :)
My articles were intended as lessons in basic Perl for those who wanted an
easy start. The exercises were purely incidental. I believe that a column
of the sort that Pablo suggested would garner an audience over time - it may
even get a good jump-start right away.
[[Thomas]] - Sometimes allusions were made in the earlier editions of TAG for
readers' to try out ideas if they were so inclined, and do post their results
in. Some did, but not many.
It's worth a try, for sure. I am greatly cynical though, so do not be surprised
if the response you get from it is low at best. You never know, you might
get a 'good' month in it.
[[[Ben]]] - Why not leave off the discouraging grumbling, and see what happens?
Thomas, there are no positive outcomes to be served by carping in this case,
and lots of negative ones. Why do it?
[[Thomas]] - I assume (since it's your suggestion) you'll be detailing to us
in more detail the sorts of things you were meaning, with an example? Yes? Excellent.
[[[Ben]]] - In fact, if Pablo does decide to undertake this, I would rather he
didn't detail them. Granting him the same courtesy that we do to any author
means leaving the details to him up until the moment that he submits the finished
article. There's no reason whatsoever to demand them until that point.
[[[[Thomas]]]] - I wasn't saying that. From what Pablo is saying, I get the impression
that he would like us at TAG to critique the answers?
[[[[[Ben]]]]] - Actually, that was my suggestion. I saw these two birds, and I only
had the one stone...
[[[[Thomas]]]] - If that's so, then that sounds like a good idea to me (is this
positive enough?) I'm just curious, that's all. Heck, it's an interesting discussion.
[[[[[Ben]]]]] - You bet. :) Encouraging participation is a plus in my book.
[[[[[[Pablo]]]]]] - I can't believe I got you two to write this much. If I tell my wife
that in top of doing my Ph.D, changing diapers and starting 2 companies I am
going to be involve in writing a column she will divorce me right away. I am
seriously tempted but let me see what I
can seriously manage and I'll get back to you.
By the way Ben, your intro to scripting in bash is excellent.
Speaking of taking over the world...
Benjamin A. Okopnik (ben at linuxgazette.net)
Tue May 2 06:41:53 PDT 2006
Answered by: Ben, Martin, Suramya, Thomas
"Gee, Brain - what are we going to do tonight?"
"The same thing we do every night, Pinky - try to take over the world."
So, my nefarious plan is this: let's all write a column (yep, I've
definitely caught the bug from the idea proposed by that querent, WhatsIsName,
recently.) What I'm talking about is creating a monthly thread in which we walk
through a common Linux task - anybody is welcome to toss in the seminal idea
and the first part of it (I'll take dibs on 'Installing a printer' this month
:), and the rest of us can pitch in comments: different ways to do it, solutions
to problems that could come up during the process, hardware/software quirks
to watch out for, etc. At the end of each month, I'll format the whole thing
into an article - I still need to figure out the layout, perhaps something highly
structured with lots of footnotes - and the credit will go to all the members
of TAG who participated.
What do you all think?
[Thomas] - I think it's a nice idea -- and something that's worth having a
go at. ;)
[[Ben]] - A pleasure to see you positive and first out of the gate, Thomas.
:) Very cool indeed.
[Martin] - That would be a interesting idea... Certainly would like to know
more about modern day printing...
All I have to do with the distro I use is select a printer and it sets it
up. I presume I'm using Cups although I'm not too sure...
[[Ben]] - Well, that is the way it often works - but that's not something from
which you can learn a whole lot. However, I'm more interested in the times when
it doesn't work that way; I've run into a lot of those over time, and have learned
quite a bit out of that. I'm definitely hoping that other people can contribute
something from their less-than-perfect experiences as well.
[[[Martin]]] - Luckily every distro I've tried has drivers for my printers but
I still would like to find out how it all works without...
[Suramya] - Sounds like a great idea.
Followup: [LG#127] mailbag #4
Ganesh Viswanathan (gv1 at cise.ufl.edu)
Thu May 25 19:02:29 PDT 2006
Answered by: Ben, Neil, Thomas
[ This is a followup to the question I
have a question about rm command. from LG#127. -- Kat ]
My reply for the:
"I have a question about rm command. Would you please tell me
how to remove all the files excepts certain files like anything ended with .c?"
question:
Hey,
The simple command (bash)
rm *[!.c]
would work for deleting all files except the right?
For all directories also, one can use:
rm -rf *[!.c]
Whatsay?
--Ganesh
[Thomas] - Assuming you had:
shopt -s extglob
set.
> For all directories also, one can use: rm -rf *[!.c]
I'd use find, since the glob will just create you unnecessary headaches if
the number of files are vast.
[[Ben]] - That would be my solution as well. In fact, since I'm a fan of "belt
and suspenders"-type solutions for shell questions of this sort ('rm' is
quite ungracious; it does exactly what you tell it to do - I'd have sworn
I've heard it chuckle at me...), I'd use 'find' and 'xargs' both.
[Neil] - [Quoting Ganesh]:
> The simple command (bash)
> rm *[!.c]
> would work for deleting all files except the right?
That doesn't look right to me. I would expect that to delete all files, except
those ending in '.' or 'c', so it would not delete example.pc or example.
> For all directories also, one can use:
> rm -rf *[!.c]
That will probably delete far more than you want. The glob expression is
evaluated by the shell in the current directory. The rm command does not see
the expression "*[!.c]", it sees whatever list the shell has created
from
that expression, so if you had a directory containing readme.txt, and
subdirectories src and module1, rm will get the command line "rm -rf
readme.txt module1" and will delete everything in module1, including files
ending in .c. The subdirectory src won't be matched, because, as I said
above, it doesn't match anything ending in 'c'.
Here's a little demo:
neil ~ 07:51:14 529 > mkdir /tmp/test
neil ~ 07:51:26 530 > cd !$
cd /tmp/test
neil test 07:51:31 531 > mkdir src
neil test 07:51:38 532 > mkdir module1
neil test 07:51:45 533 > echo -n > readme.txt
neil test 07:51:52 534 > echo -n > example.pc
neil test 07:51:58 535 > cp readme.txt example.pc src/
neil test 07:52:06 536 > cp readme.txt example.pc module1/
neil test 07:52:09 537 > ls -lR
.:
total 8
-rw-r--r-- 1 neil users 0 May 26 07:51 example.pc
drwxr-xr-x 2 neil users 4096 May 26 07:52 module1
-rw-r--r-- 1 neil users 0 May 26 07:51 readme.txt
drwxr-xr-x 2 neil users 4096 May 26 07:52 src
./module1:
total 0
-rw-r--r-- 1 neil users 0 May 26 07:52 example.pc
-rw-r--r-- 1 neil users 0 May 26 07:52 readme.txt
./src:
total 0
-rw-r--r-- 1 neil users 0 May 26 07:52 example.pc
-rw-r--r-- 1 neil users 0 May 26 07:52 readme.txt
neil test 07:52:16 538 > rm -rf *[!.c]
neil test 07:52:27 539 > ls -lR
.:
total 4
-rw-r--r-- 1 neil users 0 May 26 07:51 example.pc
drwxr-xr-x 2 neil users 4096 May 26 07:52 src
./src:
total 0
-rw-r--r-- 1 neil users 0 May 26 07:52 example.pc
-rw-r--r-- 1 neil users 0 May 26 07:52 readme.txt
neil test 07:52:30 540 >
Multiple append= Directives in /etc/lilo.conf
moped (moped at sonbeam.org)
Thu Apr 6 10:13:41 PDT 2006
Answered by: Ben
I found a web page with your subject comment, but I couldn't find where
you actually explained how to do it. Can you put a per-image append kernel option
in lilo.conf? Or does something like that have to be done all on one line, as
you suggest?
Could you please give me more info on how to do this?
Thanks!
[Ben] - Sure; here's a copy of the relevant part from my own "lilo.conf":
# Set the default image to boot
#
default=Linux-new
image=/boot/vmlinuz
vga=0x317
label=Linux-new
append="quiet acpi=on idebus=66 hdc=ide-scsi"
read-only
image=/boot/vmlinuz.old
vga=0x317
label=Linux-old
append="quiet acpi=on idebus=66"
read-only
image=/boot/vmlinuz-2.6.8-rc3-bk4
label=Linux-2.6.8
vga=0x317
append="resume=/dev/hda2 quiet acpi=on idebus=66 hdc=ide-scsi"
read-only
Each image entry gets its own 'append' option. This is also documented in
the LILO documentation; under Debian, the '/usr/share/doc/lilo/Manual.txt.gz'
file contains several examples as well as an explanation of the option.
Kmail mystery
Neil Youngman (ny at youngman.org.uk)
Fri Apr 28 01:00:48 PDT 2006
Answered by: Neil
[ Neil found his problem immediately, but I thought that the
TAG readership would like to see his nicely clueful help request, anyway. -- Kat ]
I noticed this morning that kmail was sending messages via postfix
on my machine, not via my ISP's mail server and as a consequence some emails
weren't being delivered because it's a dynamically allocated IP. this was unexpected
because
a. I thought kmail was set up to deliver via my ISP
b. postfix was set up for local delivery
First off I reconfigured postfix (dpkg-reconfigure postfix) to make
sure that it was configured for local deliveries only. This made no difference
that I could see.
I then checked my kmail configuration. Under the accounts/sending tab,
I saw that none of my sending accounts were marked as the default. That was
unexpected, but seemed like a reasonable explanation for the problem. I selected
the sending account for myisp and retested. It still sent via my local postfix
program.
I took a closer look and that account had no hostname set. I'm starting
to wonder how my kmail settings got into this state. I fix it and retest. It
still goes via my local postfix! I stop and restart kmail, check the settings
and retest. No change.
I am now completely at a loss. I search through all the visible kmail
settings and I can't see any other settings that should affect how my email
is sent.
My default sending account has the hostname for sending email set to
mail.myisp.com. I can telnet to the SMTP port at mail.myisp.com, but kmail insists
on sending mail to localhost. Why? at am I missing?
[Neil] - I am mistaken. The last 2 emails did go via my ISP, so somewhere along
the line kmail picked up the change and I misread the logs.
How to recursively search HTML?
(m at de-minimis.co.uk) m at de-minimis.co.uk
Wed May 17 20:13:40 PDT 2006
Answered by: Ben, Francis, Thomas
Dear LinuxGazette,
Can you recommend a tool for recursively searching for a a given word
starting at a given HTML page?
Google's great when on the web, but when I
have HTML on my local machine Google can't get to it.
It should be reasonably easy to script something together using wget,
awk
(to get rid of anything that's not meant to be seen), and grep, however
if there are already nice solutions out there one might as well use those.
Best Wishes, Max
[Thomas] - Do you just mean the content? Open it up in a browser. If it's
the actual HTML, use an editor.
[Francis] - If you want to have content served by your web server searchable
on an
ongoing basis, then the best answer is probably to run a local search
engine, such as htdig or swish-e (or, presumably, many others).
If you want content on my web server to be searchable, I'd prefer if you
didn't fetch everything without asking me first.
"web server" there is for three things: get at the content initially
for indexing; provide an interface to the search utility for searching; and
allow the search utility present a link to the original content for retrieving.
None of the three requires a web server, but for search engines which expect
to be used on a web site you may need to make non-default configurations if
you want your primary interface to be file: urls instead of http: ones.
> It should be reasonably easy to script something together using wget, awk
> (to get rid of anything that's not meant to be seen), and grep, however
> if there are already nice solutions out there one might as well use those.
If it is to be a one-off or rare search, then "find | xargs grep"
on the filesystem should work. The equivalent through the http interface would
also work. ("find" becomes "print a list of urls"; that
then would go through a url-retriever like wget or curl to spit the content
to stdout for grep; if grep matched, you'd want to print the matching url
for later consideration.)
In either case, you'll effectively be searching all of the content every
time.
You can get your search engine to search all of the content once, and then
tell you where to look for specific terms. The larger the volume of content,
the sooner it will have been worth indexing it initially.
[Ben] - I suppose it depends on what you mean by "recursively" -
for many webpages, enough recursion depth means searching the entire web.
I don't know of anything like that already made up, but as you say, it should
be easy enough to script. My first cut would be something like 'wget' piped
into 'lynx -dump -nolist' plus 'grep' to filter the output - but YMMV.
Cannot read Kingston USB pen drive with DOS and Mac partitions
Sindi Keesan (keesan at grex.cyberspace.org)
Sun May 14 10:15:13 PDT 2006
Answered by: Thomas
Someone asked for our help repartioning/reformatting (to FAT16) a Kingston
DataTraveler Elite 256MB USB 2.0 pen drive which currently contains one
DOS partition of about 200MB that can be accessed via a Mac (which was
used to delete the files in it), and a 50MB or so Mac partition that
cannot be reformatted by the Mac. (Something is greyed out).
The drive was apparently given out by a TCF bank at a conference and
one
of the partitions is labelled TCF_2005.
usb-storage.o identifies it as Model: TCF_2005 and Type: CD-ROM
I was told that DOS USB drivers also found it as CD-ROM, and Windows
XP
or 2000 found DOS and Mac partitions. Our DOS drivers did not find it at
all on our older computers. We have only USB 1.0 ports.
I attempted to use the Slackware 10.2 bare.i kernel with hfs.o (Mac
file
system) module, which has no dependencies listed in modules.dep.
I use Slackware-4.0- and uClibc-based Basiclinux 3.40 and
Slackware-7.1-based Basiclinux 2.1 with glibc upgraded to 2.2.5.
When I insmod hfs.o:
Unresolved symbol: generic_file_llseek
generic_commit_write
unlock_new_inode
generic_read_dir
block_read_full_page
__out_of_line_bug
block_sync_page
cont_prepare_write
event
mark_buffer_dirty
block_write_full_page
iget4_locked
generic_block_bmap
(copied via pencil and paper - how do I save such messages to a file?).
hfsplus.o gave twice as many lines of messages.
I found only four references to the first three lines in google/linux
and
they were for later kernels.
The drive comes with Windows or OSX security software which I suspect
is
causing the problem.
I cannot use fdisk without first finding the drive as a device.
Is it possible to repartition this drive with any linux?
Sindi Keesan
[Thomas] - Why insmod? That's not really the best way to go. You almost
certainly want to use modprobe so that any dependant modules needed
by the one you're trying to load, do so.
> (copied via pencil and paper - how do I save such messages to a file?).
They'll appear in /var/log/messages.
> hfsplus.o gave twice as many lines of messages.
I presume with the same content as the above?
> I found only four references to the first three lines in google/linux
> and they were for later kernels.
>
> The drive comes with Windows or OSX security software which I suspect
> is causing the problem.
>
> I cannot use fdisk without first finding the drive as a device.
Such things will appear as mass storage devices. Usually via
hotplug, they'll be assigned one of the /dev/sda* mappings. In
fact, hotplug is something that is both useful and a PITA. For
kicks, try resetting it, removing your pen drive first, and then
reinserting it:
sudo /etc/init.d/hotplug restart
(if you don't know what sudo is, or don't have it setup, you'll have
to su to root to do the above.)
You should look at the output from 'dmesg' to see what else it says
about your device. Something you haven't even bothered to tell us
(but that's OK -- everything is about guessing around here) is the
kernel version you're using. Guess what mass storage devices use?
Go on -- you might even get a gold star out of it. No? Ok, it's
SCSI. In the 2.4.X kernels, you'll need some sort of emulation
layer to do this -- scsi_mod probably.
If you're in 2.6.X, you don't have to worry about that.
> Is it possible to repartition this drive with any linux?
It is -- but this is 200MB we're talking about here...
PHP and Apache
clarjon1 (clarjon1 at gmail.com)
Fri May 12 12:29:22 PDT 2006
Answered by: Ben, Thomas
Hey gang, hope you can help
I am running Slackware 10.2 with the default apache and php stuff that
came with the installation. I am having a few troubles with PHP. I have done
what I have read I am supposed to do, the modules are loaded, but when I goto
view a PHP doc via the server, I get either a blank page or a Download To box
(depending on the browser, and what page it is) Any suggestions? I would really
appreciate.
Thanks!
(PS, I can't wait to finish writing my first article to submit to LG!
:) )
[Thomas] - [Quoting clarjon1]
> I have done what I have read I am supposed to do, the modules are
Really? And just what have you read?
You can't have done everything correctly. This symptom is usually the result
of Apache not knowing how to deal with that file type. I am going to make
an assumption here in that you really have got the PHP modules loaded. Of
course, since you don't tell us which version of Apache you're using, it makes
things slightly harder. I don't use Apache2 (way overhyped), so for Apache
1.3.X, you have to ensure in your /etc/apache/httpd.conf file, you have something
like:
AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps
[[Clarjon1]] - Sorry for not specifying what all the versions are, I was at
school at the time, and was pretty rushed for time.
[[[Thomas]]] - It happens.
[[Clarjon1]] - I have Apache 1.3.33, and I have those modules loaded in both
mod_php and httpd.conf, so I actually get errors about the modules already loaded,
[[[Thomas]]] - This is normal, and quite harmless. Which version of PHP are you
using?
[[Clarjon1]] - The AddType lines, I have those added into the httpd.conf file,
and the application/x-httpd-php stuff in the mimetypes file as well (without
the AddType there, of course)
[[[Thomas]]] - Right.
[[Clarjon1]] - The module is there, I think that it could be that I messed something
up somewhere in installation, and it's biting me now. I'm gonna try downloading
fresh copies of apache and php later today, and compile from the source when
I get home.
[[[Thomas]]] - Possibly overkill. It's probably not the applications per se that
are causing your issue, but one of misconfiguration. I would not have said that
recompiling anything is going to help, but YMMV.
[[Clarjon1]] - One last question, what sort of errors should I look at in the
error/access logs for hints as to what is going wrong? Thanks for taking the
time to help, guys. I really appreciate this.
[[[Thomas]]] - There probably won't be any errors, since Apache is doing exactly
what you asked it to do (i.e. with a misconfiguration, or no configuration,
it will attempt to either display the php file, or give you the option of downloading
it). I actually have a multitail window open (via sshfs) that tails both /var/log/apache/{access,errors}.log:
multitail -I /mnt/var/log/apache/errors.log -I \
/var/log/apache/access.log
It's quite useful for things like this. :P
[[[[Clarjon1]]]] - Thanks for all your help, but I was able to fix the problem.
Turns out I had all the configuration files set up correctly, I was
missing some files. I don't know why nothing complained, but oh well.
I went through the packages from my other distros I have kicking
around, and I found this package:
libphp_common432
This package provides the common files to run with different implementations
of PHP. You need this package if you install the php standalone package or
a webserver with php support (ie: mod_php).
I installed it, and viola! I now have PHP working. I got a little forum set
up (after finding mySQL was broken and then had to install postgres, then
figuring out how to use postgres and the database and users which can be used
via web). I'm glad that's over with.
So all is good for now, with this problem Thanks again for your help!
[Ben] - As Thomas said, it sounds like you don't have the PHP filetypes defined
in your 'httpd.conf' - or perhaps the relevant module is missing or not enabled.
On Debian, this happens automatically as part of the PHP package installation
procedure; presumably, Slackware doesn't do that, so you'll have to do it manually.
In my /etc/apache2/apache2.conf, the relevant entries look like this:
DirectoryIndex index.html index.cgi index.pl index.xhtml index.php
Include /etc/apache2/mods-enabled/*.load
I'd also ensure that there was a 'php5.conf' and a 'php5.load' in my /etc/apache2/mods-enabled/
directory. For plain Apache (i.e., not
Apache2), the above would be more of a direct reference from 'httpd.conf'
and would look something like
AddType application/x-httpd-php .php
AddType application/x-httpd-php-source .phps
LoadModule php5_module /usr/lib/apache/1.3/libphp5.so
(This would, of course, require that the module named above existed at that
location.)
Something I've also found helpful in my PHP travails of the past (this wouldn't
help in your case, since the problem you're having comes before this level
of troubleshooting) is having a file called 'info.php' living somewhere in
my web hierarchy and consisting of the following:
<?php
phpinfo();
?>
Once PHP is up and running, looking at this file will give you lots and lots
of info about your PHP installation and its capabilities.
Printer setup
Neil Youngman (ny at youngman.org.uk)
Sat Apr 1 00:01:28 PST 2006
Answered by: Ben, Martin, Neil
I upgraded to the latest SimplyMepis a while back and since then I've
been unable to get it to configure my printer. IIRC, when I originally set up
Mepis I just installed some extra packages to give it the right drivers and
configured it in the CUPS web interface at localhost:631.
The printer is a Xerox XK35C, for which the lex5700 driver is recommended.
Searching the debian packages for xk35c, I find foomatic-db and foomatic-filters-ppds
seem to have relevant files. Having made sure both are installed, I still don't
get the Xerox Workcentre XK35C or the Lexmark 5700 on the list of available
printers.
The HOWTOs don't offer anything more than install the correct driver
package and configure printer. Does anyone know what I'm missing here?
[Martin] - Have you re-started CUPS?
/etc/init.d/cups restart
Sometimes you have to re-start Cups for it to see any new drivers then just
select the printer in the web interface...
[[Neil]] - This machine is not usually left on overnight, so it's been rebooted
quite a few times since the drivers were installed.
[Ben] - Check to make sure that your system (via hotplug) still detects your
printer. Examine the output of 'dmesg' for something like this:
usb 2-1: ep0 maxpacket = 8
usb 2-1: default language 0x0409
usb 2-1: new device strings: Mfr=1, Product=2, SerialNumber=3
usb 2-1: Product: psc 1310 series
usb 2-1: Manufacturer: hp
usb 2-1: SerialNumber: CN522C5230V4
usb 2-1: uevent
usb 2-1: device is self-powered
usb 2-1: configuration #1 chosen from 1 choice
usb 2-1: adding 2-1:1.0 (config #1, interface 0)
usb 2-1:1.0: uevent
usb 2-1: adding 2-1:1.1 (config #1, interface 1)
usb 2-1:1.1: uevent
usb 2-1: adding 2-1:1.2 (config #1, interface 2)
usb 2-1:1.2: uevent
drivers/usb/core/inode.c: creating file '002'
hub 2-0:1.0: state 7 ports 2 chg 0000 evt 0002
uhci_hcd 0000:00:1d.0: suspend_rh (auto-stop)
hub 3-0:1.0: state 7 ports 2 chg 0000 evt 0000
drivers/usb/core/inode.c: creating file '001'
usblp 2-1:1.1: usb_probe_interface
usblp 2-1:1.1: usb_probe_interface - got id
drivers/usb/core/file.c: looking for a minor, starting at 0
drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 2 if 1 alt 0 proto 2 vid 0x03F0 pid 0x3F11
usbcore: registered new driver usblp
drivers/usb/class/usblp.c: v0.13: USB Printer Device Class driver
Also (assuming that it's a USB printer and you have 'usbfs' configured and
mounted), take a look at '/proc/bus/usb/devices'; my printer entry there looks
like this:
T: Bus=02 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 3 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
P: Vendor=03f0 ProdID=3f11 Rev= 1.00
S: Manufacturer=hp
S: Product=psc 1310 series
S: SerialNumber=CN522C5230V4
C:* #Ifs= 3 Cfg#= 1 Atr=c0 MxPwr= 2mA
I: If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=cc Prot=00 Driver=(none)
E: Ad=01(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms
E: Ad=81(I) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=82(I) Atr=03(Int.) MxPS= 8 Ivl=10ms
I: If#= 1 Alt= 0 #EPs= 3 Cls=07(print) Sub=01 Prot=02 Driver=usblp
E: Ad=03(O) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=83(I) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=84(I) Atr=03(Int.) MxPS= 8 Ivl=10ms
I: If#= 2 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
E: Ad=07(O) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=87(I) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=88(I) Atr=03(Int.) MxPS= 8 Ivl=10ms
I: If#= 2 Alt= 1 #EPs= 3 Cls=ff(vend.) Sub=d4 Prot=00 Driver=(none)
E: Ad=07(O) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=87(I) Atr=02(Bulk) MxPS= 32 Ivl=0ms
E: Ad=88(I) Atr=03(Int.) MxPS= 8 Ivl=10ms
If all the hardware stuff is OK, try printing directly to the device:
cat /etc/group > /dev/usb/lp0
If that works, then the problem is (obviously) CUPS. I've wrestled with that
thing myself, in the past, and here's what worked for me:
Check /etc/cups/ppd to make sure that you have the correct PPD file. If you
do, and 'cups' still fails to detect your printer, go to http://linuxprinting.org
and grab a fresh copy of that PPD file - I've had the distro install a stale
version that couldn't handle my (brand new) printer twice now, with two different
printers.
[[Neil]] - No it's not USB
[Ben] - There's also a 'HOWTO'-type page at the above URL that walks you through
the intricacies of dealing with CUPS and FooMatic stuff that you might find
helpful.
[[Neil]] - I've looked at that before, but this time I found enough inspiration
to solve it. The PPD file hadn't been installed where CUPS could see it.
[[[Ben]]] - Now that you remind me - yeah, shortly after I installed CUPS a
couple of years ago, I had the same problem. The PPD I needed was located somewhere
deep inside '/usr/share' or /usr/lib', but CUPS just ignored it. I think it
was that FAQ at linuxprinting.org that finally put me onto the fact that it
should be in '/etc/cups/ppd' instead.
[[Neil]] - I located the PPD file with
find / -xdev -iname \*xk35\*
and then I copied it to /usr/share/cups/model/
root at 2[~]#
gunzip /usr/share/ppd/linuxprinting.org-gs-builtin/Xerox/Xerox-WorkCentre_XK35c-lex5700.ppd.gz
root at 2[~]#
cp /usr/share/ppd/linuxprinting.org-gs-builtin/Xerox/Xerox-WorkCentre_XK35c-lex5700.ppd /usr/share/cups/model/
root at 2[~]# /etc/init.d/cupsys restart
Restarting Common Unix Printing System: cupsd.
root at 2[~]#
After that I was able to configure it from the web interface.
Easy once I looked in the right place. Thanks for getting me on the right
track.
[[[Ben]]] - Glad I could help, Neil!
Reading Oxygen Phone Manager files
Jimmy O'Regan (jimregan at o2.ie)
Thu May 25 08:17:43 PDT 2006
Answered by: Ben, Francis, Jimmy
Every now and then I use a Windows program called "Oxygen Phone
Manager" to back up my phone. It's able to read information that none of
the Linux programs can, so it solves the problem of how to back up everything
on the phone, but uses some strange file formats of its own, which is another
problem...
This script converts data from
the call registry to the XML format that OPM outputs (.cll files, or [mnt point]/Program
Files/Oxygen/OPM2/Data/Phones/[phone IMEI]/CallRegister.dat).
This is probably the least useful information that OPM extracts, but
I needed to use it to understand the date format OPM uses, and someone somewhere
might find it useful.
[Jimmy] - It turns out that at least one other program uses the same date
format, so the date stuff is probably more useful than I'd thought.
Anyway, here's a Python version of the date
stuff (I use python as a hex editor :)
[Francis] - Hi there,
I think there are some imperfections in the homebrew date code (which is
why there are modules for that sort of thing, of course).
As a verification, 36524 days after 1 Jan 1900 should be 1 Jan 2000 (100
years x 365 days per year plus 24 leap days between those dates).
My date(1) doesn't go back as far as 1 Jan 1900, but 1000 days later is 28
Sep 1902, so I can use that as an independent verification.
$ date -d "28 Sep 1902 + 35524 days" +%d/%m/%Y
01/01/2000
print days_since_1900(36524);
-2/01/2000
So: homebrew perl is a few days out, and it prints negative numbers.
> sub split_date
> {
[snip]
> # Number of days since 1900
> if (eval "require Date::Manip")
> {
> import Date::Manip qw(DateCalc Date_Init);
>
> # OPM doesn't seem to use proper leap years
> $numdays -= 2;
[snip]
> }
[snip]
> else
> {
> # My crappy function, as a last resort
> days_since_1900 ($numdays);
> }
[snip]
> }
>
> if ($buggy_as_hell)
> {
> # 38860.8914930556 should be 23/05/2006 21:23:45
> split_date(38860.8914930556);
That'll give 23/05/2006 because you subtract 2 within split_date when using
Date::Manip, as shown above.
38860 days after 1 Jan 1900 is actually the 25th. It's only worth mentioning
because you don't explicitly subtract 2 within days_since_1900.
> sub days_since_1900
> {
> my $numdays = shift;
> my @mdays = qw(31 28 31 30 31 30 31 31 30 31 30 31);
>
> my $years = int($numdays / 365);
Minor point -- after 366 leap years have passed, that'll be off.
Unlikely to be a major problem.
> if ($buggy_as_hell) {print "$years years\n";}
>
> $numdays -= ($years * 365);
That's $numdays %= 365, "the number of days gone this year plus the
number of leap days since epoch".
> if (($years % 4) == 0)
> {
> $mdays[1] = 29;
> }
Other minor point -- that's strictly wrong; but for the range of "90
years either side of today" it works, so it's also unlikely to be
a major problem.
> if ($buggy_as_hell) {print "February has $mdays[1] days\n";}
>
> my $leapyears = int ($years / 4);
> if ($buggy_as_hell) {print "$leapyears leapyears\n";}
> $leapyears++; # Um... 'cos this doesn't count 1900 as OPM does
Don't know exactly what OPM does, but $leapyears is now "the number
of leap days since epoch, plus one, plus one more if this is a leap year but
it's not yet Feb 29th" which is probably not a very useful count.
> $numdays -= $leapyears;
The big problem is here. $numdays can now be negative, which will lead to
odd dates come December -- try 39050 and 39060 and spot the awkwardness.
So: if $numdays is less than 1, decrease $years by 1, increase $numdays by
365 (or 366 if the new $years corresponds to a leap year), and then think
about how to handle the "if this is a leap year but it's not yet Feb
29th" thing.
Oh, and maybe subtract the 2 that happens in the Date::Manip case.
It's too much to wrap my head around right now, so I'll just suggest the
cheaty
$numdays -= 1000;
$date=qx{date -d "28 Sep 1902 + $numdays days" +%d/%m/%Y};
as a shell-out workaround.
And the magic OPM "2"? Maybe it counts 1 Jan 1900 as day 1 not
day 0, and maybe it thinks 1900 was a leap year? That could bump the current
numbers up by 2 compared to what is expected, perhaps.
The same algorithmic error is in the python implementation.
[Ben] - I didn't have the time to dig into it, but two errors jumped out at
me:
import Date::Manip qw(DateCalc Date_Init);
Ummm... don't do that. Just don't. The reasons are long and complex (see
'perldoc -f import', if you feel like unraveling a tangled string), but that
should be 'use Date::Manip qw(DateCalc Date_Init);' instead.
You've also got 'xml_line' being invoked as
while (<>)
{
s/\r\n//;
my ($type, $order, $number, $foo, $name, @times) = split (/\t/, $_);
xml_line ($type, $number, $name, @times);
}
but declared as
my ($type, $number, $name, $stimes) = @_;
my @times = split / /,$stimes;
Given your sample data, you're putting a single time string into '@times',
then reading it as a scalar. The easiest fix (well, 'problem prevention' rather
than 'fix' - it'll work as it is unless a "\t" gets into the time
data) would be to invoke and process it as a scalar:
my ($type, $order, $number, $foo, $name, $times) = split (/\t/, $_);
xml_line ($type, $number, $name, $times);
or, perhaps, by completely eliding those temp vars since they're only used
once anyway - which would eliminate the problem as a side effect:
while (<>)
{
s/\r\n//;
xml_line ( ( split /\t/)[0,2,4,5] );
}
Network Traffic Review/Filtering
sloopy (sloopy_m at comcast.net)
Thu Apr 6 04:27:56 PDT 2006
Answered by: Francis, Kapil, Suramya
Greets and Salutations,
I have lurked about on the ML for quite a while and wanted to thank
all that make this source of info (and at times humor) for their time and knowledge.
The question(s)
I run a 8-10 node network at home through a router (a VIA C3 mobo with
fedora core) and would like to have a way of setting up a web page on it that
would list URL's being retrieved from the inet, and a nice side option of being
able to block certain content for some nodes on the network. would i need to
run a proxy (i.e. squid or similar) for this? or would this be over the capabilities
of the router machine?
thanks,
sloopy.
[Francis] - Hi there,
I have lurked about on the ML for quite a while
Great -- I'll not explicitly Cc: you since you're on the list already.
Short answer: you do not need to run a proxy, but you should do so. And it
should not exceed the capabilities, unless you've other funny stuff going
on.
Longer answer follows...
Usually, the hard part about designing a solution is precisely specifying
the intention ;-)
that would list URL's being retrieved from the inet
will need to have access to those URLs.
I'm guessing that you primarily care about http, with perhaps an interest
in https or ftp too.
Expect that you won't see details of https requests. It's easier that way.
One way to get access to those URLs would be to run a network sniffer on
the router and configure it to record HTTP requests.
Completely passive, no change to what the users see or do, and you can prevent
the system becoming swamped by allowing it to drop packets if it thinks it
is too busy, at the cost of not having a complete record of the accesses.
Google will be able to suggest software which can do this, if you don't have
any favourites. One variant I've come across (but can't think of right now)
involves sniffing and displaying any images in http traffic that are on the
network. That may or may not be appropriate for your setup, of course.
[[Suramya]] - The software you are thinking about is called Driftnet
.
Be really really careful while running this. We tried this as a test at my
last job and were showing off the program to a group of co-workers and I guess
someone in the building was surfing porn at that time so we got to display
some really explicit content on a really big display.
Consider yourself warned if you want to use this... :)
[Francis] - Another way to get the URL list would be to require the use of a http proxy
server, and read the log file it generates. One way to require the use of
a proxy server is to allow (web) access from it and block access from elsewhere.
Another way is to try network magic on the router and use a transparent proxy.
(With the obvious caveat that a transparent proxy can't work in all cases;
that may not be an issue for you.)
Small or no changes to what the users see and do. Active, in that if the
extra service fails, web access is stopped. And it does allow for the possibility
of caching and access control, if you go that way.
In either case, for a web page, "tail the-url-list-file" as an
appropriate user might be sufficient, or just show the raw log file, or use
any of the log analysers to generate pretty pictures. Again, Google will likely
show you a ready-made solution for whichever you pick.
being able to block certain content for some nodes on the network.
When you have defined (for yourself) "certain content" and "some
nodes", you'll probably find that it's easier to do this at the http
level, with a proxy server. It can be done at the tcp level with a more active
network sniffer, but the simple answer is "don't do that".
On my machine (PII 366MHz, 128MB) I use squid as a caching proxy server,
with squidGuard as a redirector intended primarily to block some images and
undesired content. Single client node, and (deliberately) easily bypassed.
(I also have a thttpd to serve the redirected content, for completeness.)
In my setup, the control is handled mostly by squidGuard, which can decide
based on source address or url, but not based on content. That's good enough
for me. (There's a Fine Manual with all of the details.)
Occasionally I want to make local modifications to the block-or-allow lists,
which I do from a shell. A webmin module for it exists if you like that kind
of thing, but I've not examined it in a long time.
"My users" is "me", and they all know how to fix or work
around broken bits without bothering their admin. This happy state may not
match your network.
Extra memory is always good. And disk space if you choose to cache or retain
logs. But if the machine can run Fedora Core, it can run squid/squidGuard
for a small network.
Set up squid and squidGuard and whatever other bits you want, and use it
as your proxy server. Configure squid to allow what you want to allow, and
block the rest. Configure squidGuard to allow or block as appropriate. And
make sure that "what you want to allow" won't surprise the other
users.
Admire your URL list web page, and change it to match what you want.
Decide how important to you it is to block access and have a full log of
http requests.
Then either invite others to use the proxy, require others explicitly to
use it, or require others transparently to use it (the latter two include
adjusting your ip filtering rules).
And when it's all working, if you've something to add over what's in the
lg archives, write it up as an article and submit.
Good luck with it!
[[[Kapil]]] - As Suramya pointed out anecdotally, in any (re-)configuration of
routers/firewalls make sure you understand and can handle the "politics".
As Francis Daly said you have three solutions. I'll add a glimpse to the
politics associated with each.
a. Force all nodes to use a web proxy by blocking other nodes from accessing
the web directly (using firewall rules). Any web proxy combined with a log
analyzer (analog?) can do what you want.
Provide a ".pac" file (for automatic proxy configuration) for
user convenience.
This way everyone using the nodes knows what you are doing and how.
b. Automatically redirect web connections from the nodes to the web proxy
by firewall rules. You need a web proxy (like squid) that can handle "transparent
proxying".
The users need not be told anything but they'll probably find out!
"Transparent" proxying is generally not quite transparent and
in my experience does break a few (very few) sites. Note that web proxies
are acounted for by the RFC for HTTP but transparent proxies are not.
c. Use firewall rules to send a copy of all web traffic through a sniffer
which can extract the URL's. You can insert firewall rules to block/allow
specific IP addresses.
Again the users need not be told anything.
You will not be breaking any network protocols by doing this.
Hope this helps,
Meaning of overruns & frame in ifconfig output
Ramon van Alteren (ramon at vanalteren.nl)
Thu Apr 6 13:41:50 PDT 2006
Answered by: Ben, Francis, Martin, Ramon
Hi All,
Out of pure interest would anyone know the exact definition (or provide
me with pointers to said definition) of the fields overrun and frame in the
output of ifconfig.
I've been searching google for an answer, but that mostly turns up
false positives from all the people over the years that have posted their ifconfig
output on the internet.
I've checked wikipedia which has an external link to the following
short bit on overruns but nothing on the frame field: "Receiver overruns
usually occur when packets come in faster than the kernel can service the last
interrupt. "
I'm seeing these (overrun & frame errors) on a NIC in a load-balancer
which services just the incoming http-requests (outgoing uses direct routing)
and I'm buying new ones tomorrow. I am however still curious what these values
actually mean.
Thanx,
Ramon
[Francis] - The source code might :-)
[[Ramon]] - Kept that as a last resort, my C coding & reading skills is
at best rusty and at worst non-existant.
[Francis] - But there's a 450 kB 45-page pdf at both
http://www.utica.edu/academic/institutes/ecii/publications/articles/A0472DF7-ADC9-7FDE-C80B5E5B306A85C4.pdf
and http://www.computer-tutorials.org/ebooks/02_summer_art1.pdf
with the heading
International Journal of Digital Evidence
Summer 2002, Volume 1, Issue 2
"Error, Uncertainty, and Loss in Digital Evidence"
Eoghan Casey, MA
which includes on p29
One manufacturer provides the following information about interface errors,
including datagrams lost due to receiver overruns a.k.a. FIFO overruns (NX Networks,
1997).
* packet too long or failed, frame too long: "The interface received
a packet that is larger than the maximum size of 1518 bytes for an
Ethernet frame."
* CRC error or failed, FCS (Frame Check Sequence) error: "The
interface received a packet with a CRC error."
* Framing error or failed, alignment error: "The interface received
a packet whose length in bits is not a multiple of eight."
* FIFO Overrun: "The Ethernet chipset is unable to store bytes in
the local packet buffer as fast as they come off the wire."
* Collision in packet: "Increments when a packet collides as the
interface attempts to receive a packet, but the local packet buffer
is full. This error indicates that the network has more traffic than
the interface can handle."
* Buffer full warnings: "Increments each time the local packet
buffer is full."
* Packet misses: "The interface attempted to receive a packet,
but the local packet buffer is full. This error indicates that the
network has more traffic than the interface can handle."
[[Ramon]] - Mmm interesting link, more reading material for the stack ;-) Thanks
[Francis] - This is friend-of-a-friend third hand stuff by now, of course,
but it certainly sounds reasonable to me, and might give you pointers to some
more terms to search for to find something demonstrably authoritative.
For what it's worth,
/proc/net/dev packet framing error overrun
was what I was what I (eventually) asked Google for, before asking for
"NX Networks" ifconfig
which found the two links.
I hope the above isn't useless.
[[Ramon]] - Certainly not, at the very least it will serve to enlight my soul
with knowledge, which is a good thing (tm)
FYI: It took me awhile to pinpoint this bottle-neck, most answers google
turned up pointed to badly configured or malfunctioning hardware and or pci-busmaster
stuff.
This is a well-configured Intel 100Mbit NIC with busmastering enabled which
is apparently flooded with http-traffic to the point that it can not generate
interrupts fast enough to get the frames out of it's buffer. That's the first
time I've ever seen that.
[[[Martin]]] - DOS attack was the first thing that came to mind...
[[[Ben]]] - I've seen NICs from nominally reputable vendors start throwing a large
number of errors under a much lower load than what you've described - I tested
several identical units and gave up in disgust. The Intel cards that I used
to replace them worked great, never a complaint. The one you described is just
an amazing sample of the breed; it should be given a retirement dinner, a gold
watch, and a full pension.
[[[[Ramon]]]] - It's an Intel NIC
;-)
[[[[Martin]]]] - So what would cause a network card to throw that many errors then?
I'm guessing that its either dodgy drivers or a actual dodgy manufacture...
[[[[[Ben]]]]] - The latter. This happened ~7 years ago, but since I had to send the
cards to the States to get them replaced (I was in the USVIs at the time), and
everything took place in S-L-O-W T-I-M-E, many of the details are still with
me. It all took place under a certain legacy OS, but the drivers that the vendor
specified (ne2000) were the bone-standard, came-with-the-OS types. By the time
the third card arrived - I had a hard time believing that I got two bad cards,
but seeing trainwrecks happening at 2MB/s was a pretty strong motivator to find
out - I had installed Debian (dual-boot) on my machine, and could show the NIC
falling over and twitching piteously under two different OSes. Then, I marched
into the CEOs office with a couple of printouts and demanded a case of Intel
NICs. I had no experience with them personally, but I had a number of trustworthy
admin friends who swore by these things while swearing off everything else.
Oh yeah - I should mention that the CEO of that company was convinced that
the IS department should be able to run on, oh, fifty cents a month - and
asking for anything more was an outrage and a shuck that he was way too smart
to fall for. This led to some interesting confrontations on a regular basis
- I suppose he liked high drama. Anyway, I don't recall if I had to resort
to bodily harm and talking about his mama, but I got those cards and spent
the week after that installing them on every machine in the company (except
the CEOs, he-heh. He had a brand-new Dell for his Minesweeper and Solitaire,
and had previously told me that he didn't want me to touch it.)
After The Great Replacement, many of my network troubles disappeared - and
as a bonus, so did lots of database problems. Seems that many of the latter
were caused by apps establishing a lock for the duration of the transaction
+ the network flaking out during that transaction. This would cause the lock
to persist until that machine was rebooted (!), and nobody else could get
access to that DB until it was... this was a Novell 4.01 goodie that fortunately
went away when I updated everything to 4.11, months later.
[[[Francis]]] - (quoting Ramon): Kept that as a last resort, my C coding
& reading skills is at best rusty and at worst non-existant.
As backup for the "random file on the web" info, /usr/include/linux/netdevice.h
on my 2.4-series machine includes in the definition of "struct net_device_stats",
in the "detailed rx_errors:" section
unsigned long rx_frame_errors; /* recv'd frame alignment error */
unsigned long rx_fifo_errors; /* recv'r fifo overrun */
which seems consistent with that information. (Similar entries appear in
a few other headers there too.)
And egrep'ing some nic drivers for "rx_frame_errors|rx_fifo_errors"
reveals notes like "Packet too long" for frame and "Alignment
error" for fifo.
So if it's wrong, it appears consistently wrong.
As to the cause of the errors -- fifo overrun, once the nic is configured
and negotiated right, might just mean "you have a (seriously) large amount
of traffic on that interface". Presumably you've already considered what
devices might be generating that traffic, and isolating things on their own
network segment. An alternative is that the machine itself is too busy to
process the interrupts and data, but you would likely have spotted that sooner.
Frame alignment, on the other hand (again, presuming that it isn't just an
artifact of a nearly-full buffer) suggests that some other device is generating
a dubious frame. Any consistent pattern in source MAC or IP which can be used
to point the finger?
[[[[Ramon]]]] - Nope the reason I couldn't believe the error at first sight is that
it is NOT failure behaviour. It simply is legit traffic ;-)
It's the external nic on the load-balancer for the website I work for. It's
pulling 9M+ pageviews per day with a 12 hour sustained peak of 500K+ pageviews
per hour. All that traffic needs to go through this single 100Mbit interface,
in large amounts of small http request packets.
I'm swapping it out for a Gigabit card later today.
We'll probably frame the card as an achievement and hang it somewhere around
the office :-D
Search Engine Spiders
bob van der Poel (bvdp at xplornet.com)
Thu Apr 20 16:46:45 PDT 2006
Answered by: Ben, BobV, Francis, Jason, Thomas
Any light on how search engines like google work? I've recently moved
my web stuff to the free site provided by my new ISP. For some reason google
refuses to list any of my "really good stuff". And, doing some searches
I don't think that any other (or very few) pages on this site are being found.
My page http://users.xplornet.com/~bvdp has a fairly unique pattern I can
test "wynndel broadband xplornet". So far the only hits are back to
my OLD web pages which announce a move. BTW, those pages are gone.
I've discussed this with Xplornet and they have come to the conclusion
that their site is "sandboxed", but don't know why, etc. And, frankly,
I'm not sure they care much either :)
I have tried to "seed" things by filling out the google form
(sorry, forget the exact spot right now).
I find the whole issue pretty interesting, especially since in the
past when I've created new pages, etc. they have been found by google within
hours. Days at the most. These new pages have been up for about a month now
and not a hint from google.
[Thomas] - Probably then, the google site is listed in 'robots.txt' on the
webserver as not being valid when sending out bots to spider your site (or a
subdomain). It's a common practise to ban most harvesting bots, and to allow
only a few.
[[BobV]] - I've actually checked that out. The ISP assures me that there are
no robots.txt files buggering things up. I should have mentioned that in my
original post, I guess.
[Thomas] - Google work by sending out spiders -- programs that essentially
use referral-following (URL-hopping if you like) to see what's what. The greater
linked your site is, the greater the chance you'll get'spidered'. (I am sure
this is explained on google's site. Go and look).
> searches I don't think that any other (or very few) pages on this site
> are being found. My page http://users.xplornet.com/~bvdp has a fairly
> unique pattern I can test "wynndel broadband xplornet". So far the only
> hits are back to my OLD web pages which announce a move. BTW, those
> pages are gone.
So? Even if your site is hit by google (or some other indexing surveyor)
that's still no guarantee your search results will show up. Consier a company
such as Google. Do you have any idea just how much data they house? Whenever
you goto 'www.google.com', and perform a search -- you're connecting to a
different cache of information each time, so the results you get returned
for a known search may well differ. And note that "specific" !=
"likely chance of singular hit". In fact that's quite the opposite.
If your site is the only one listed with a specific phrase, and has not been
referenced elsewhere on the net for google to pick up, what do you think the
chances of it being listed are?
> I've discussed this with Xplornet and they have come to the conclusion
> that their site is "sandboxed", but don't know why, etc. And, frankly,
> I'm not sure they care much either :)
To me it's a moot point, and is slightly egotistical to want to see your
site on a search engine. If that happens all well and good. Doubtless it might
happen eventually.
[[BobV]] - Of course it is moot. Which is why I posted this message. Figured
it might of some interest to others. Sorry if you think I'm just being egotistical
or whatever.
[Jason] - Quoting BobV, "Any light on how search engines like google
work?"
Well, you start with a novel concept and a bunch of really smart people.
Then you leverage commodity hardware and open source software to create a
superior product with a clean, simple design. You dominate the market, go
public, and then you sell out your principles to help China suppress free
speech...
...oh, you mean *technically*? No idea. :-)
[Ben] - Well, there's a surefire way to find out if Google knows about you:
ben at Fenrir:~$ google http://users.xplornet.com/~bvdp
Sorry, no information is available for the URL users.xplornet.com/~bvdp
* If the URL is valid, try visiting that web page by clicking on the following link: users.xplornet.com/~bvdp
* Find web pages that contain the term "users.xplornet.com/~bvdp"
I guess it doesn't. I'm assuming you went to http://www.google.com/addurl.html
to add yourself - yes? And you made sure to put in a list of keywords that
are relevant to your site - yes? I've always found this to work just fine
for my clients, although it does take up to a couple of weeks (and it's amazing
how impatient people can get in the meantime. :)
[[BobV]] - Yes, that's what I did. I also tried to set up a site map but it
appears that I need permission to run python on the site for that to work. I
can't run anything on the remote site, so that is out.
[[[Francis]]] - All the site map is is a list of links, yes? Probably with some
organisation and grouping and background and the like, but fundamentally, a
link to every page on one page? (And the hrefs shouldn't start with "http://",
and probably shouldn't start with "/" either, for portability.)
Do you have a local copy of the web site content? If so, you can run a local
web server configured similarly to the public one, and run the site map generating
program against that. (Or use "find" with some extra scripting,
but that uses a file system view rather than a web client view of the content.)
That should lead to one or a few html pages being created; upload them to
the public site and you're laughing.
[[[[BobV]]]] - Yes, I think you have it pretty much correct. I've not bothered to
'dl the code ... I don't see that it does me much good to know how simple my
simple little site is :) But, you idea of running in on the local site and then
putting the results on my public site crossed my mind as well. Unless they have
some checksums/tests in the code it should work fine.
[Ben] - So, try submitting to a bunch of other engines in the meantime. They
all "steal" from each other, AFAIK - and the more places there are
on the Web that refer to your site, the higher the chance that Google will run
across it sooner.
[[BobV]] - You know, I get to used to using google that I forget that other
engines even exist. Just for fun, I tired yahoo and, interestly, it found the
site.
So, it probably is just a matter of time.
[[[Ben]]] - This should also provide a bit of reassurance on Google's score: if
Yahoo indexed you, then so will they - in their own good time.
2[BobV]- Honestly, this is not a big deal with me. I do contribute some software
and ideas which I suppose other folks might be interested in (which is why it's
on the web). I'm just trying to understand (at a low level) how these search
spiders work. I wonder, with all the computing power that something like google
has ... how long would it take to "spider" the whole web? They are
already referencing billions of pages and my mind gels thinking of how many
links that might involve, let alone keyword combinations.
[[[Ben]]] - Oh, it's fun (and at least somewhat mind-boggling) to think in those
terms. I mean, just how much space does the Wayback machine (which takes regular
snapshots of just about everything on the Net) have? More interesting yet, when
will that kind of capacity - and data-processing capability - become available
to us consumer types?
"Say, Bob, do you happen to have the latest copy of the Net? I think
I'm a bit behind; just beam me your version if you don't mind..."
4 [BobV] - Did I read somewhere, recently, that someone was marketing a disc
(HD?) with "the net" on it. Well, a very small subset of the net :)
I think this was for folks who didn't have broadband or something. Seemed like
a silly idea to me.
So, which is growing faster ... consumer storage or the size of the net?
I'd bet on the net! Mind you if we take all the porn, music, duplicate pages
and warez software off the net ... well, gosh, then there would be nearly
nothing left.
[[[Francis]]] - Do you have access to the web server logs? Ideally the raw logs,
which you can play with yourself; but even the output of one of the analysers
may be enough.
[[[[BobV]]]] - Unfortunately, no. Just a dumb site from this end.
[[[Francis]]] - If you can see the HTTP_USER_AGENT header in the logs, you'll
have an idea of when the search engine spiders visit. Apart from the "normal"
clients, almost all of which pretend to be some version of Mozilla, the spiders
tend to have reasonably identifying names.
[[[[BobV]]]] - Interesting. No secrets on the web :)
[[[Francis]]] - If you've ever seen "googlebot" (or however it is spelled)
visit, you can expect that they are aware of your content[*]. And if you've
never seen "yahoobot" visit (again, I'm making up the user-agent string
here -- when you see it, you'll know it) you can wonder about how they managed
to index your content.
[*] Unless it's someone playing games, using that sort of identifier in their
own web client. All of the HTTP headers are an indication only.
Whether the logs are available is up to the hosting company. And if they
are available, whether they include HTTP_USER_AGENT or HTTP_REFERER or any
other specific headers is also up to them.
But if you can get the logs, you can spend hours playing with them and finding
trends and counting visitors and seeing why "unique visitors"
is a fundamentally unsound concept. But there are almost certainly more enjoyable
ways of spending your time :-)
Good luck
[[BobV]] - Impatient ... when you say "weeks". Gosh, Ben, these days
anything more than a minute or two is an eternity :)
[[[Ben]]] - [laugh] Well, there is that. Most people have been trained to expect
instant gratification these days (athough many claim that instant is too slow
in the Internet Age), and a couple of weeks might as well be a lifetime. Although
I understand that a baby still takes nine months, no matter how hard you work
at it. It's all so confusing...
Quoting from the classic "Story of Mel",
Mel loved the RPC-4000 because he could optimize his code: that is, locate
instructions on the drum so that just as one finished its job, the next would
be just arriving at the "read head" and available for immediate
execution.
I suspect that your previous experiences happened when your part of IP space
(or whatever other system Google uses to sequence their spiders) was just
about to "arrive at the read head". This is, I assure you, not the
usual case. :)
Profile has errors
K1 (research.03 at gmail.com)
Thu Apr 13 16:21:06 PDT 2006
Answered by: Thomas
Hi:
I am new to IPCOP and am learning it while setting it up, I wonder
if you can point me to asomeone who can help me.
Your article was very informative, but my issue is with DSL.
I have Verizon DSL and am using a Westell Versalink 327W. I am utilizing
the red and green interfaces.
My IPCOP box is handing out addresses as I have DHCP enabled, but I
get time out errors when I try to ping it . When I access it from a browser
on the green interface I get "Current profile-Non" and "the profile
has errors".
When I view the log on my Westell I see my ipcop box. Help what am
I doing wrong?
[Thomas] - What are these 'red and green interfaces'?
What about using ''traceroute'' instead? What's your network topology like?
Are you using a gateway (perhaps some form of NAT?) Do you handle your own
DNS? You need to be much more thorough in the information you detail to us.
Sounds like you need to read the IPCop userguide, or somesuch then.
You're not telling us what's in the logs, for starters. We're not mind
readers -- and knowing what's in this file, might just help provide pointers
as to its solution.
Where can I find GLUE (Group of Linux Users Everywhere)
Shlomi Fish (shlomif at iglu.org.il)
Sat May 6 19:56:15 PDT 2006
Answered by: Ben, Rick, Shlomi
Hi!
I am the dmoz.org editor of the Linux Users' Group category. Recently,
GLUE (Group of Linux Users Everywhere) has disappeared from the Net. What is
its status and when will it be restored? Does it have a new URL?
Regards,
Shlomi Fish
[Ben] - Well - hi, Shlomi! Pleasure to hear from you.
(Shlomi Fish is a long-time contributor to the Perl community; lately, for
example, I've enjoyed his contributions on the "Perl Quiz-Of-The-Week"
list - so it's a pleasure to be able to give what help I can in return, little
though it may be in this case.)
A quick search of the Net seems to indicate that GLUE was being hosted by
our former webhost, SSC with whom we parted ways quite a while back.
[[Shlomi]] - I see.
[Ben] - According to the Wayback Machine, though, whatever arrangement they
had never amounted to much:
http://web.archive.org/web/*/http://www.ssc.com/glue/groups/
My best suggestion for anyone looking for a LUG is to take a look at the
{ http://www.linux.org/users/[LUG Registry]} - but I'd imagine that you already
know that. As to GLUE, my best guess is that they're gone.
[[Shlomi]] - I see. Well, I'll try to find out at SSC.
[Rick] - Hi, Shlomi. Ma nishma? ;->
[[Shlomi]] - Hi. Ani Beseder.
[Rick] - GLUE seems to have been completely eliminated in the most recent Web
site reorganisation at SSC. When that happened, because I reference it in the
Linux User Group HOWTO, I looked in vain for any sort of explanation, so I suppose
none will be forthcoming.
[[Shlomi]] - OK. Thanks. I'll try to find out more at SSC.
Graham Jenkins
Derek (derek.davies at telco4u.net)
Sun Apr 30 11:46:14 PDT 2006
Answered by: Ben, Thomas
Dear Gang, Can you help me ?,my old school friend Graham Jenkins moved
to Australia many years ago ,is he your Graham Jenkins?.
My friend was born in Hereford England on the third of April 1940,attended
Lord Scudamores boys school has three sisters.
This may be a shot in the dark,but I would like to see the old fellow
again before I pop my clogs.
I have been trying to find him for quite a while.
hope you can help
Derek Davies
[Thomas] - You could always look at his author page, and email him. IIRC he
might be claiming to be from Australia.
[[Ben]] - That is indeed what his bio says; "a Unix Specialist at IBM Global
Services, Australia... lives in Melbourne".
http://linuxgazette.net/authors/jenkins.graham.html
> My friend was born in Hereford England on the third of April 1940,attended
> Lord Scudamores boys school has three sisters.
[[Ben]] - The picture in his bio looks a bit younger than that, but it's plausible.
[Thomas] - Scudamores' school, eh? I know of it through reputation.
> This may be a shot in the dark,but I would like to see the old fellow again
> before I pop my clogs.
[Thomas] - That sounds like an awfully odd thing to say.
[[Ben]] - Google shows 981 usages. :)
[Thomas] - I must admit that your question is singularly unique. ;) I don't
think Jenkins is a member of TAG. If you'll permit us to do so, we'll add this
to the Gazette Matters section of LG.
[[Ben]] - I note (again, via Google) that Graham is quite active in the Perl
community and elsewhere. Perhaps emailing him at the address on his page would
be the most efficient way of getting hold of him.
Request for any ADC's driver source code
osas e (osas53 at yahoo.com)
Sat May 20 10:43:13 PDT 2006
Answered by: Thomas
Hello,
I am a student doing a project and want to interface an ADC0804 to
a PC’s parallel port to read the humidity value of the atmosphere. Knowing
that there are professionals like you out there, I am writing to request a driver
source code to read from this or any other ADC using a PERL Program. It is my
belief that you will be kind enough to help a newbie like me grow in computer
interfacing.
Kind Regards
Ediae Osagie
[Thomas] - Tell us more about this project. Does your project also stipulate
that you yourself have to work out how to interface an ADC0804 to the paralell
port?
As a "professional" (and a student) it is usually a given that
a student does their homework beforehand. How is it you heard of us, anyway?
You can't have read the Linux Gazette, since you'd know that we don't do others'
homework. You're no different from this.
Having done some electronics in the past (these are just pointers for you
to consider), interfacing to the paralell port is relatively easy -- assuming
you do so in an appropriate language. C for instance has many different routines
to achieve this, and in fact, any simple I/O system can read and write to
/dev/lp* as is necessary. Try it. That's the only "driver" you'll
really need.
Enjoy your homework -- we won't help you do it.
Talkback: Discuss this article with The Answer Gang
Published in Issue 128 of Linux Gazette, July 2006
The LG Talkbacks
Talkback:122/sreejith.html
[ In reference to the article Stepper motor driver for your Linux Computer in LG#122 ]
(jovliegen at gmail.com) jovliegen at gmail.com
Sun Apr 16 05:20:36 PDT 2006
Answered by: Ben, Jason
Hello, First of all, I like to thank you guys for this great "Gazette".
I realy do enjoy it !!!
I'm trying to build the stepper motor driver, that you published
in issue 122. While reading the code, I have a little remark. I'm not quite
sure that I'm right, but ... what do I have to loose :D
On line 20 : "static int pattern[2][8][8] = {"
Shouldn't that be pattern[2][2][8] ?
Like I said before, I'm not sure of this ... just wondering ...
Thanks again for your nice work, all of you
[Jason] - Thanks! It's great to hear from readers.
I went and looked at that author's code, and it sure looks like you're right.
Note that it doesn't hurt anything to declare the array as larger than you
need it, but it's probably not the best style.
There's a few other things in that code that I might have done differently.
For instance, his "step" function looks like this:
int step()
{
if(k<8) {
// if(pattern[i][j][k]==0) {
// k=0;
// printk("%d\n",pattern[i][j][k]);
// k++;
// }
// else {
printk("%d\n",pattern[i][j][k]);
k++;
// }
}
else {
k=0;
printk("%d\n",pattern[i][j][k]); /*#####*/
k++; /*#####*/
}
return 0;
}
Note that this does not have the exact same behavior as the original function.
In the original function, after step() returns, k is in range [1,8], inclusive.
In the version I give, k is kept in the range [0,7], inclusive, which is the
correct range if k is being used as the index of an array of length 8.
Unless I'm really missing something, I don't think the actual code to write
the parallel port was included in that article.
Thanks for taking the time to point this out.
[[Ben]] - As I recall, the author used a shell script to prod the device.
Talkback:123/jesslyn.html
[ In reference to the article uClinux on Blackfin BF533 STAMP - A DSP Linux Port in LG#123 ]
Robin Getz (rgetz at blackfin.uclinux.org)
Sat May 6 09:09:25 PDT 2006
Answered by:
In http://linuxgazette.net/123/jesslyn.html Jesslyn Abdul Salam
wrote:
>The Blackfin processor does not have an MMU, and does not provide any
>memory protection for programs. This can be demonstrated with a simple program:
This is only true if you leave this feature turned off.
The Blackfin processor does include hardware memory protection, which
the uClinux kernel supports - but since it effects performance, and most embedded
developers only turn this on when doing development, and it is turned off
by default.
http://docs.blackfin.uclinux.org/doku.php?id=operating_systems#introduction_to_uclinux
When you take:
int main ()
{
int *i;
i=0;
*i=0xDEAD;
printf("%i : %x\n", i, *i);
}
and run it on the Blackfin/uClinux, you get:
root:~> uname -a
Linux blackfin 2.6.16.11.ADI-2006R1blackfin #4 Sat May 6 11:38:53 EDT 2006
blackfin unknown
root:~> ./test
SIGSEGV
Which is pretty close to my desktop...
rgetz at test:~/test> uname -a
Linux test 2.6.8-24.18-smp #1 SMP Fri Aug 19 11:56:28 UTC 2005 i686 i686
i386 GNU/Linux
rgetz at test:~/test> ./test
Segmentation fault
Talkback:124/dutta.html
[ In reference to the article Interfacing with the ISA Bus in LG#124 ]
Abhishek Dutta (thelinuxmaniac at gmail.com)
Mon May 8 01:11:49 PDT 2006
Answered by: Ben, Thomas
Hi,
Could you please change address my website in the article http://linuxgazette.net/124/dutta.html
published in MArch,2006 issue of linuxgazette.net
You can get more details and photos related to this project at http://www.myjavaserver.com/~thelinuxmaniac/isa
The website address has changed from mycgiserver.com to myjavaserver.com
--
Abhishek
[Thomas] - I wouldn't have thought so. Most of the mirrors have probably synched
by now, not to mention copious other sources. By changing your article now,
that's be known as a fork -- something not desirable at all.
[[Ben]] - Even more importantly - since 'creating a fork' for already-published
content doesn't bother me much - it would be essentially pointless; we currently
have nearly 60 mirrors and several translation sites, and the only site that
we can change is ours (i.e., the root site.) In other words, even if we change
it - which I'll do, since it's trivial - anyone searching for your article will
still be about 70 times more likely to find the old address rather than the
new one.
For anyone contemplating writing an article, this is why I encourage including
the pertinent images, sources, etc. as part of the submission: external links
die. The author's details - including the URL in their bio - are flexible,
since the bios are reloaded monthly by all the mirrors; the article content,
once published, is essentially frozen in time.
[Thomas] - The best you can hope for is that I/we/someone publishes this request
in the gazette for next month. ;) Of course, given that the talkback feature
points here, and not to your personal address, you can at least be assured that
any correspondence will reach us and not some void.
[[Ben]] - Excellent point, Thomas! I hadn't considered that particular benefit
of it.
Talkback:124/smith.html (7)
[ In reference to the article Build a Six-headed, Six-user Linux System in LG#124 ]
Eric Pritchett (eric at gomonarch.com)
Mon Apr 24 15:07:31 PDT 2006
Answered by: Ben, Jimmy, Karl-Heinz
How would you configure this setup to use usb speakers for each
user. I think the ideal solution would be to have a usb keyboard with a built
in usb hub that has two usb slots, so you can plug in your mouse and usb speakers.
Any thoughts?
[Jimmy] - That would solve the simpler problem: that of having the speakers
close
to the user; it wouldn't address the other difficulties of using
multiple sound cards: of ensuring that the intended sound is directed to
the correct sound card, in particular.
Ob. mailing list requests: please don't send HTML email (there's a not-so-tenuous
connection between postal workers and the frequenters of mailing lists: you
have been warned :), and should you reply, please don't top post: top posting
makes the Baby {Jesus, Buddha, Xenu, etc.} cry. :)
If you understood my first paragraph, feel free to stop reading, as (bearing
in mind that e-mail to this list is intended for publication) there is a fairly
common misconception here; otherwise: USB is smart, but not that smart -
the fact that devices are located close to each other physically is not communicated
to the OS (that is, the system can't tell that soundcard A is connected to
keyboard A, soundcard B to keyboard B, etc.), which is therefore unable to
act accordingly.
[[Karl-Heinz]] - If the keyboard is its own hub -- the usb tree hierarchy should
be quite able to mirror the physical proximity. I've not read the beginning
of this thread -- but I can imagine a setup with two heads and two keyboards
where "usb speakers" are dedicated to sound produced on one of the
heads.
Just don't expect a standard distribution to do this for you -- this is manual
configuration and it can not be saved in the users settings (like kde) if
the users could be on either head.... pam extensions like group setting on
login for devices like audio might be able help with the setup.
[[[Ben]]] - Interesting idea, that. I can imagine a system - something like LDAP
in general scope if not in implementation - that assigns configured user resources
from the available pool... hm, wish I knew a bit more about creating a project
like that. It wouldn't even have to involve kernel programming, since everything
could be done at the USB level.
Talkback:124/smith.html (8)
[ In reference to the article Build a Six-headed, Six-user Linux System in LG#124 ]
Claude Ferron (cferron at gmail.com)
Thu Apr 27 05:30:25 PDT 2006
Answered by: BobS
any update on the bugs you were experiencing?
[BobS] - Not really. There is a new nVidia driver which does not fix the problem.
Two members of the Xephyr project have written to say that the problem I'm seeing
is due to a reset problem in the nVidia driver. Their solution is to run several
X sessions inside one big X session. This way the boards only get reset once.
The URL for Xephyr is at: http://www.c3sl.ufpr.br/multiterminal/index-en.php
.
Talkback:124/smith.html (9)
[ In reference to the article Build a Six-headed, Six-user Linux System in LG#124 ]
Izzy esteron (izzyesteronjr at yahoo.com)
Sun May 21 06:58:01 PDT 2006
Answered by: Ben, Izzy
To whom it may concern,
This article by Mr. Smith is amazing. In my opinion, this is the solution
all 3rd world countries are looking for to keep hardware cost down. I know the
technology is not perfect yet, but it is a great start.
Anyway, does this setup allow each workstation to have their own audio?
How about network/LAN gaming?
Thank you for your time,
izzy
[Ben] - Well, the former was noted as a problem in the article; there has also
been some discussion on the issue. What it looks like to me is that it would
be possible to make this available with a little work in the kernel - but it
would either take someone experienced in audio and kernel hacking, or convincing
the current maintainers that this is necessary. Conversely, individual external
(USB) sound devices might be a solution.
The latter does not seem like it would be a problem at all as long as the
CPU and the memory is up to it; most of the load in gaming, as I understand
it, is on the video card - and every user has one of their own in that configuration.
[[Izzy]] - Thanks for the reply, it was really helpful.
Last February Mr. Smith posted a message on http://blog.chris.tylers.info
. He mentioned that
"The system is VERY unstable. I get a kernel oops
fairly often when a user logs out. Has anyone seen
this problem before? Any ideas on how to fix it? Also,
any suggestions to improve my article?
thanks,
Bob Smith"
Also, there was a couple of replies after this message and showed how to
solve the problem by downgrading the nvidia drivers. Has Mr. Smith tried the
"fixes"?
Thanks again.
Talkback:125/collinge.html
[ In reference to the article HelpDex in LG#125 ]
Diego Roversi (diego.roversi at gmail.com)
Tue Apr 4 01:49:33 PDT 2006
Answered by: Ben, Rick, Suramya
I can see the comics. What's wrong with the old good image formats?
Why not PNG or JPG?
[Rick] - Guys, plainly we need to FAQ this.
Diego, this was discussed in the prior issue (#124). Please see: http://linuxgazette.net/124/misc/nottag/flash.html
Note open-source (reverse-engineered) Flash implementations in various degrees
of completion, detailed at http://osflash.org/ . Note also excellent and
authoritative analysis by Kapil Hari Paranjape at the first URL cited. (Kapil
views HelpDex using the open-source swfplayer software, which he finds adequate
to the task. I recommend that plus the Flashblock browser extension, http://flashblock.mozdev.org/,
so that you retain the ability to view Flash only when you wish, not when
some advertiser so dictates.)
Diego, you're welcome to work with us every month to convert the Ecol comic
strip to formats you prefer -- without the results sucking, please -- or become
a cartoonist and start sending us good cartoons in a graphics format you prefer.
Otherwise, your answer would seem to be as above.
[[Ben]] - I don't know that an FAQ entry would be of much use; in my estimate,
the percentage of our readers who have looked at our FAQ is very small.
[[[Rick]]] - Interestingly, one of the less-appreciated but substantial benefits
of a FAQ has nothing to do with whether people ever bother to read it before
asking its questions or re-raising its tired old subjects. That is: When somebody
does go there for the 1000th time, you can definitively answer, with near-zero
effort, with just a URL.
[[[[Ben]]]] - Which presumes remembering the URL in question... but I do see your
point. That "secondary" use of the FAQ has even more benefits than
I thought - all natural consequences, to be sure, but my mind wasn't quite twisty
enough to see all the rami. In short, kudos.
[[[[[Rick]]]]] - Why, thank you, sir.
You might enjoy the slightly cranky bit of documentation that I posted to
the prototype wiki replacement for Silicon Valley Linux User Group's Web site
(on one of Heather's machines), starting with header "Standards, Nits,
Peeves" on this page:
http://gemini.starshine.org/SVLUG/Teams/Web_Team
I was definitely getting in touch with the curmudgeon within, when I wrote
this entry:
website/Website: No such word. Correct to "Web site".
No, there's nothing wrong with inventing new words, especially where
they make our language more expressive and fill a need not met by
existing words. This one doesn't qualify, and is really just the result
of people being sloppy. Some would call our cleaning it and similar
things off our pages "prescriptivism"; I prefer the term "leadership".
[[[Rick]]] - Over the years, I've used this trick to dispose of innumerable topics
after getting tired of discussing them. My first-level expectation is that hardly
anyone will read my answers until I send their URLs. Note: I do take advantage
of that expectation to expose readers to adjoining text on related questions.
[[[[Ben]]]] - Sneaky. And useful.
[[Ben]] - However, it might make sense to add some sort of a note regarding
this issue to the top of the strip. I'll give the wording some thought and glue
it in.
[[[Rick]]] - My opinion, yours with a small fee and disclaimer of reverse-engineering
rights: Less is better. E.g.,
'' Format: Flash ''
...where "Flash" is anchor text hyperlinking to a FAQ, for which
http://linuxgazette.net/124/misc/nottag/flash.html might serve nicely.
Metacomment: Computerists tend to overestimate public willingness to deal
with explanatory text. The public at large tends to react badly to verbosity,
assuming its contents to be
- unimportant, and/or
- open to debate
This is why we have "STOP" signs, rather than "Stop, though
of course there are lots of exceptions including the need to do anything required
to avoid dangerous situations" signs.
[[[[Ben]]]] - [laugh] Kat just finished her Power Squadron course (scored 100% on
her test, woo-hoo!); this is almost exactly the phrasing used for right-of-
way rules in navigation. Which is why, I suspect, so many people screw up in
that regard.
[[Suramya]] - Umm... I have a low tech approach to converting the Ecol comic
strips from flash:
Click on the link to view the flash file, take a screen shot and save it
in the format you want. Sample output:
http://www.suramya.com/Temp/HelpDex.jpg
:)
If I get the files early enough I volunteer to do this. But let me know what
you think of this...
[[[Ben]]] - 1) At the moment, there's no way to do actual thumbnails linked to
full-size images in the cartoon section. Changing that would require twiddling
Mike's Python scripts - and I'd have no idea how to do that.
2) JPG files are significantly larger than the equivalent SWFs - and go all
jaggy when viewed at anything but "native" size (unless, of course,
you go with an even larger file size.) E.g.:
:-r!ls -l /tmp/Help*
-rw-r--r-- 1 ben root 80715 2006-04-06 12:50 /tmp/HelpDex.jpg
-rw-rw-rw- 1 ben root 18546 2005-12-06 21:21 /tmp/HelpDex.swf
Add a thumbnail to that, and we've got a big chunk'o'download - for no gain
(and, in fact, image quality loss.)
3) The issue is - except for the very rare complaint - settled. There's Open
Source viewing software available, which seems to work fine, and those who
complain will now be redirected (either from here or from the link on the
page itself) to the discussion covering it.
So - thank you for the offer, Suramya, but there's no need. It's all good
to go.
Talkback:125/howell.html
[ In reference to the article A Brief Introduction to IP Cop in LG#125 ]
André Fellows (andrefellows at hotmail.com)
Tue Apr 11 13:43:21 PDT 2006
Answered by: Ben
Hi folks!
This IP Cop is another leaf of the Linux Firewall/Router/DHCP server distros.
I have to tell you that this IP Cop seems to me not good as BrazilFW.
I used Coyote (http://www.coyotelinux.com/ ) but it was discontinued.
The BrazilFW (www.brazilfw.com.br)
is the Coyote continuation.
Try there, its free, fast and painless!
Cheers
Fellows
[Ben] - Then the obvious thing to do is a bunch of research comparing the two
and presenting your results in an article. Otherwise, thank you for telling
us how it "seems" to you... but I'm not sure why you'd want to share
this information. [1]
I've used Coyote in the past on several occasions, and liked it a lot; for
basic routing and firewalling, it was quite a nice gadget. However, IPCop
has many more features than Coyote did - at least so I gathered from the article.
DIfferent pieces of software, different purposes. One is not "better"
than the other - just different. Implying otherwise, especially without supporting
data, is rather inconsiderate toward the person/people who took the time to
write the software that you don't like.
[1] This is a (perhaps somewhat testy) way of pointing out that saying "program
$X is good" does NOT require adding "because program $Y sucks"
for the purpose of emphasizing the former; there's no subordinate clause implied.
Since this is not the world of proprietary software, in which vendors are
fighting tooth and nail to sell their latest crap-a-riffic bugware, *we do
not have to denigrate competing software* - it brings us, as a community,
no benefit, and may do damage to a fellow programmer's reputation. So, yeah,
this hits the rant button for me.
[[André]] - My sincere excuses!!!
I forgot to mention that my "seems" is not to consider!
[[[Ben]]] - Relax - my mini-rant was a generalized one. I replied to your statement,
but it's about more than that; it's about an important consideration for the
Linux community in general. We should always be striving to support each other,
not tear each other down.
Often, operating in the world of Open Source requires re-thinking the "standard"
ways of interacting with the other people involved. This differs from what
we're generally used to, but is usually easy to adapt to: substituting cooperation
for competition, especially when the benefits are obvious and immediate, presents
little difficulty for most people.
It does, however, require thinking about it ahead of time - which is what
I'm trying to get people to do with my rant. Thanks for the opportunity. :)
[[André]] - My intention was to tell you guys about the BrazilFW, the
Coyote sucessor. Like Coyote, BrazilFW have many addons to improve its funcionality.
The "seems" part was because I thinked you guys could make an article
comparing both and its funcionalities.
[[[Ben]]] - Well, we don't generally write articles - but we do accept well-written
ones on Linux-related topics. If you'd like to write one about BrazilFW, I'd
be happy to look at it.
[[André]] - This is the point of the information. Really sorry if I wasn't
clear (and I really wasn't ).
Very very very sorry to make you Benjamin spend your time on mine nonsense
comparison...
[[[Ben]]] - Don't worry - there was nothing particularly awful in your email,
and I wasn't upset.
[[André]] - Oh, by the way, Linuxgazette is a GREAT SITE with GREAT information!!!
[[[Ben]]] - Thank you, André! We do our best. Glad to hear that you're
finding it useful.
Talkback:126/cherian.html (1)
[ In reference to the article Preventing DDoS attacks in LG#126 ]
Thomas Adam (thomas at edulinux.homeunix.org)
Tue May 2 13:49:25 PDT 2006
Answered by: Ben
Hello,
I was intrigued by this article about DDoS. It's something one hears
about more and more, and so I thought I'd give it a go, and play along at home.
Ben, I don't know just what percentage of the original article remains, having
done the rewrite on it (something that I agree with, especially in terms of
attribution), but I would have liked it if the original author could have expanded
on a few things...
* Check if your CPU load is high and you a have large number of HTTP
process running
Heh. Yes, I quite agree. But so what? I mean, how are you supposed
to distinguish that from most other processing that goes on? A simple 'w' isn't
going to help you much there. It's pretty normal for most CPUs to peak.
As for the HTTP process, this is typically mitigated by setting the
following in /etc/apache/httpd.conf to a reasonable value:
MaxClients 30
Now, the Apache folks make it quite clear that this should not be set
too low, blah, blah. But for a small-end server (perhaps even one running on
a home ADSL-connection) setting this to something perhaps lower than 30 in this
case would help in stopping Apache from consuming everything.
Then there's the following command:
ps -aux|grep -i HTTP|wc -l
I know I can be pedantic at times, but on non-BSD systems the leading
'-' causes issues, not to mention the classic "You'll return grep too"
syndrome, as well as the useless use of 'wc' (this isn't for your benefit, Ben,
more the original author):
ps aux | grep -ic '[h]ttp'
* Determine the attacking network
This section was quite good. Note that, as mentioned before, the number
of concurrent connections via Apache can be capped. Again, the command:
netstat -lpn|grep :80|awk '{print $5}'|sort
Can be reduced to:
netstat -lpn | awk '/:80/ {print $5}' | sort
(Too many people seem to think Awk only understands columns in terms
of quoting printed ouput. Such a shame.)
It's worth mentioning here the use of PAM and chroots. A slight side-note
is that in any DDoS attack, the targeted process or thread is generally going
to expand as the load increases on it. This is generally undesirable, and so
one can tell PAM to employ memory usage limits via /etc/security/limits.conf
(think ulimit for processes). As for the chroots, running various processes
inside those can encapsulate their environment away from everything else.
I also couldn't see what the following code was supposed to do:
for f in /proc/sys/net/ipv4/conf/*/rp_filter
do
echo 1 > done
echo 1 > /proc/sys/net/ipv4/tcp_syncookies
I assume that's meant to read:
for f in /proc/sys/net/ipv4/conf/*/rp_filter
do
echo 1 > "$f"
done
echo 1 > /proc/sys/net/ipv4/tcp_syncookies
Hmm. This reads as though I've picked the hell out of the article for
no apparent reason -- far from it. I hope these little tidbits of information
will prove useful. By all means feel free to forward these comments on to the
other author.
[Ben] -
On Tue, May 02, 2006 at 09:49:25PM +0100, Thomas Adam wrote:
> Hello,
>
> I was intrigued by this article about DDoS. It's something one hears about
> more and more, and so I thought I'd give it a go, and play along at home.
> Ben, I don't know just what percentage of the original article remains,
> having done the rewrite on it (something that I agree with, especially in
> terms of attribution), but I would have liked it if the original author
> could have expanded on a few things...
>
> * Check if your CPU load is high and you a have large number of HTTP
> process running
> Heh. Yes, I quite agree. But so what? I mean, how are you supposed to
> distinguish that from most other processing that goes on? A simple 'w'
> isn't going to help you much there. It's pretty normal for most CPUs to
> peak.
I'm a fan of iostat/vmstat, myself - but 'w' will give you the standard
1/5/15 load averages.
That's not much to do with peaks. (Just FYI, I avoided changing the actual
content of the article as much as possible except where it was clearly wrong.
Different usage, or even suboptimal usage, I left alone. Ditto the idiom,
which is why it still sounds mostly like Blessen rather than me.)
As for the HTTP process, this is typically mitigated by setting the
> following in /etc/apache/httpd.conf to a reasonable value:
>
> MaxClients 30
>
> Now, the Apache folks make it quite clear that this should not be set too
> low, blah, blah. But for a small-end server (perhaps even one running on
> a home ADSL-connection) setting this to something perhaps lower than 30 in
> this case would help in stopping Apache from consuming everything.
Right, but he's talking about a server in a data center - I believe that
was mentioned right at the beginning.
> Then there's the following command:
>
> ps -aux|grep -i HTTP|wc -l
>
> I know I can be pedantic at times, but on non-BSD systems the leading '-'
> causes issues, not to mention the classic "You'll return grep too"
> syndrome, as well as the useless use of 'wc' (this isn't for your
> benefit, Ben, more the original author):
>
> ps aux | grep -ic '[h]ttp'
[Nod] Agreed.
> It's worth mentioning here the use of PAM and chroots. A slight
> side-note is that in any DDoS attack, the targeted process or thread is
> generally going to expand as the load increases on it. This is generally
> undesirable, and so one can tell PAM to employ memory usage limits via
> /etc/security/limits.conf (think ulimit for processes). As for the
> chroots, running various processes inside those can encapsulate their
> environment away from everything else.
Again, chrooting is something I'm a big fan of. Heather told me about
it ages back, and I glommed onto the idea like a drowning man onto a
log...
> I also couldn't see what the f
![[BIO]](misc/cover/xteddy-sitting-48.png)
![[BIO]](misc/cover/gimp.png)
![[BIO]](misc/cover/dragon.jpg)
Heather got started in computing before she quite got started learning
English. By 8 she was a happy programmer, by 15 the system administrator
for the home... Dad had finally broken down and gotten one of those personal
computers, only to find it needed regular care and feeding like any other
pet. Except it wasn't a Pet: it was one of those brands we find most
everywhere today...
