The Shell Game

It’s Official

gnukathryn — Sun, 06 Apr 2008 13:09:39 +0000

BOINC has been added to the Fedora 7 and higher repositories. You can use your favorite GUI front end or just do

# yum install boinc-client boinc-manager

The cool part is my logrotate config file is in the repositories as part of the package. I don’t know how geeky that makes me, but it sure did make me feel good. I don’t program, so there’s isn’t a whole lot I can do to give back to the Fedora community. So I think it’s cool that I was able to contribute in this small way.

Why Didn’t I Think of This?

gnukathryn — Tue, 26 Feb 2008 13:14:20 +0000

I ran across this “advertisement” on Raincoaster’s blog (note, may be somewhat NSFW at times). It was too funny, so I had to post it here. I’m not in IT, nor do I think there’s a very high probability of me working in IT. But I do know managers. And it’s scary how sometimes expensive == good in their minds. Not all managers are like this. However, I know one of the managers at my school is. Breaking up a large brick wall with my head is probably easier than trying to get her to see it any other way.

I’ve Got Mail!

gnukathryn — Mon, 11 Feb 2008 12:58:22 +0000

The capital letter in my user name was indeed throwing sendmail into fits. I could have created an entire new user. But hey, that’s a lot of work. I’d have to port my Firefox profile over and re-customize my desktop. Nah. Definitely not worth it just to be able to read local email.

I could have directly edited /etc/passwd using vipw at the command line. I’m not a big fan of vi. It scares the pants off me. I’ll stick to emacs, thanks. Heck, I find emacs extremely challenging on a good day. I’m all for the simple route of using kedit. So on the advice of mweltin who was hanging around #boinc, I ended up using usermod from the command line. The syntax was quite simple. usermod -l kathryn Kathryn. The only gotcha is that you can’t be logged into an account that you want to edit. So I logged out of Kathryn. Hmmm… well that dumped me to a text login screen. Oh well. I logged in as root, ran my usermod command and then rebooted from the command line. I have no idea how to get back into a graphical environment from a text prompt. But at least I learned how to reboot from the command line.

And…. BINGO!

[kathryn@Galaxy ~]$ mail
Mail version 8.1 6/6/93. Type ? for help.
“/var/spool/mail/kathryn”: 6 messages 6 new
>N 1 boinc@Galaxy.Fedora Mon Feb 11 19:42 17/582 “test”
N 2 MAILER-DAEMON@Galaxy Mon Feb 11 19:42 78/2716 “Warning: could not send message for past 4 hours”
N 3 MAILER-DAEMON@Galaxy Mon Feb 11 19:42 164/5257 “Warning: could not send message for past 4 hours”
N 4 root@Galaxy.Fedora Mon Feb 11 19:42 27/978 “Cron run-parts /etc/cron.daily”
N 5 logwatch@Galaxy.Fedo Mon Feb 11 19:42 113/3519 “Logwatch for galaxy.fedora (Linux)”

Picky Picky

gnukathryn — Fri, 08 Feb 2008 15:03:19 +0000

I found an answer to my mail problems. Someone hit on my blog using sendmail “user unknown” errors 8.14.1 as a search term. I figured that this person was having problems similar to my own. So I put that same search in Google and found this thread.

It looks like having a user name with capital letters in it throws sendmail into a tizzy. This fits perfectly with what I observed on my own machine. I can receive mail sent to root or boinc, but I can’t receive mail sent to Kathryn.

So I guess I need to create a new user for myself called “kathryn”. I’m just not sure what to do with all the stuff that’s in “Kathryn”.

Oh well. At least the mystery has been solved.

You’ve got mail?

gnukathryn — Wed, 06 Feb 2008 12:13:36 +0000

I recently found out that the system sends various emails to the root account. And darn it, I want to read them. In theory, all I need to do is have those emails automatically forward to my own user account (and I guess it’s also possible to have them forwarded to a regular email account). Supposedly it’s as easy as creating a file called /root/.forward with the user name of the account you want to have the mails forwarded to.

I always get sort of suspicious when someone says “It should be as easy as…”. Because, it doesn’t seem to matter how easy it is, I still have problems with it. And yes, mail didn’t disappoint.

I have two user accounts on my machine, mine (Kathryn) and BOINC’s (boinc). I can send mail to boinc and root, boinc can send mail to root and root can send mail to boinc. But neither boinc nor root can send mail to Kathryn. Apparently, I don’t exist.

[Galaxy:~]$ mail -v Kathryn Subject: test testing Cc: Kathryn... Connecting to [127.0.0.1] via relay... 220 Galaxy.Fedora ESMTP Sendmail 8.14.1/8.14.1; Wed, 6 Feb 2008 09:09:50 +0900 >>> EHLO Galaxy.Fedora 250-Galaxy.Fedora Hello localhost.localdomain [127.0.0.1], pleased to meet you 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-8BITMIME 250-SIZE 250-DSN 250-ETRN 250-AUTH DIGEST-MD5 CRAM-MD5 250-DELIVERBY 250 HELP >>> MAIL From: SIZE=35 AUTH=boinc@Galaxy.Fedora 250 2.1.0 ... Sender ok >>> RCPT To: >>> DATA 550 5.1.1 ... User unknown 503 5.0.0 Need RCPT (recipient) >>> RSET 250 2.0.0 Reset state /var/lib/boinc/dead.letter... Saved message in /var/lib/boinc/dead.letter Closing connection to [127.0.0.1] >>> QUIT 221 2.0.0 Galaxy.Fedora closing connection

I’ve jumped through a bunch of hoops trying to get this to work. I’ve tried sending to Kathryn@localhost. Nope. No dice. I’ve checked the contents of /etc/hosts. Everything is fine there. I’ve added the host name to /etc/mail/local-host-names. Nope. No dice. On advice from my tutor I’ve done `make` in /etc/mail and `newaliases` (for luck of course). No dice. I’ve even restarted the sendmail service. I must be a figment of my own imagination.

All this to read messages that look like

From root@Galaxy.Fedora Tue Feb 5 04:17:03 2008
Date: Tue, 5 Feb 2008 04:15:39 +0900
From: root@Galaxy.Fedora (Cron Daemon)
To: root@Galaxy.Fedora
Subject: Cron run-parts /etc/cron.daily
Content-Type: text/plain; charset=UTF-8
Auto-Submitted: auto-generated
X-Cron-Env:
X-Cron-Env:
X-Cron-Env:
X-Cron-Env:
X-Cron-Env:
X-Cron-Env:

/etc/cron.daily/logrotate:

[ OK ] BOINC client daemon: [ OK ]
Starting BOINC client as a daemon: [ OK ]
[ OK ] BOINC client daemon: [ OK ]
Starting BOINC client as a daemon: [ OK ]

From root@Galaxy.Fedora Tue Feb 5 04:15:28 2008
Date: Tue, 5 Feb 2008 04:15:28 +0900
To: root@Galaxy.Fedora
From: logwatch@Galaxy.Fedora
Subject: Logwatch for galaxy.fedora (Linux)
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset=”iso-8859-1″

######### Logwatch 7.3.4 (02/17/07) ##########
Processing Initiated: Tue Feb 5 04:15:27 2008
Date Range Processed: yesterday
( 2008-Feb-04 )
Period is day.
Detail Level of Output: 0
Type of Output: unformatted
Logfiles for Host: galaxy.fedora
#########################################

———– pam_unix Begin ————–

su:
Authentication Failures:
Kathryn(500) -> root: 1 Time(s)
Sessions Opened:
(uid=0) -> boinc: 5 Time(s)
Kathryn(uid=500) -> root: 5 Time(s)

———— pam_unix End —————

———– XNTPD Begin ————–

Total synchronizations 2 (hosts: 2)

———— XNTPD End —————-

———– Disk Space Begin ————–

Filesystem Size Used Avail Use% Mounted on
/dev/sda6 9.9G 3.8G 6.1G 39% /
/dev/sda8 4.0G 73M 3.7G 2% /tmp
/dev/sda7 4.0G 855M 3.0G 23% /home
/dev/sda2 60G 18G 43G 30% /Data
/dev/sda1 41G 24G 17G 59% /Vista

———— Disk Space End —————

############ Logwatch End ###############

BOINC Logrotate gotcha

gnukathryn — Thu, 31 Jan 2008 12:27:22 +0000

In a previous post, I provided the logrotate config file I use for BOINC. One “gotcha” just popped up. The script stops the daemon before doing the rotation and then starts it again. If for whatever reason you manually stopped the daemon, when cron runs logrotate, the daemon will be restarted. I’m investigating ways of dealing with this.

I’m sorry Dave, I’m afraid I can’t do that

gnukathryn — Wed, 23 Jan 2008 12:14:21 +0000

OK, OK… sorry for the bad humor in the post title.

I’ve been diving into the intricacies of Unix permissions. Up to this point, I’ve been comfortable enough with both symbolic notation (rwx) and octal notation (1,2,4). I’ve been looking at a sandboxing scheme for BOINC. That has brought up a whole bunch of questions that I’ve been working on answering.

The first thing I noticed was the use of 4 digit octal notation. The second, third and forth digits are the file permissions I’ve been dealing with since the beginning. The first digit refers to the presence or absence of setuid, setgid and the sticky bit.

setuid and setgid change the ID a program runs under. In turn that allows controls access permissions. If you have a program you want to run as a regular user (a good thing) but it needs elevated privileges to do certain things, you can use setuid and setgid to give that program the permissions it needs. Remember though, it’s a good idea to only use that to the extent it’s needed. Elevate the privileges, do what you need to do and then drop them.

The sticky bit has two usages depending if it’s on an executable file (the original usage) or a directory (today’s common usage). If it’s on a executable, it allows the binary to be shared across users (or at least that’s how I’m understanding it). If it’s on directory it allows files to be locked down to the owner and the super user. So even if you have write permission on the directory, you won’t be able to move, modify rename or delete a file if you don’t own it.

There’s also some stuff on umasks I’m trying to understand, but that’s still all a bit hazy in my mind.

I never realized Unix permissions could get so complicated.

What I’m working on

gnukathryn — Tue, 15 Jan 2008 08:22:45 +0000

I have two ongoing projects. I can only work on them in small chunks of time because of real life commitments. Both involve scripting.

My first project that seems to have been going on forever is writing a script that will let me listen to an entire genre of music in mplayer. I run mplayer from the command line. I can make a play list that will play an entire directory. But my music is arranged genre – artist – album – track. I create the playlist by doing a simple ls > playlist. Easy peasy. But if I try that in the top directory, it doesn’t work so well. Actually, it doesn’t work at all even if you recurse down the directory structure. mplayer wants full path names, not relative ones. So I was going to write a script that created the playlist file for me. But no, I get the bright idea to make this a lot harder than it has to be. I’m now trying to get the playlist built on the fly with options to choose which genre of music I want to listen to. My current (very broken) script can be found here. There is quite a bit of stuff commented out because it just doesn’t work.

My other project was inspired by a post on the wordpress.com forums. The basic question is how to figure out who are the most frequent commenters on your blog. You can get an xml dump of a wordpress.com blog. It shouldn’t (in theory) be too difficult to write something in perl or python that parses the xml and gives that information. I’ve never coded a line of perl or python in my life. So on some advice, I’ve decided on perl for this little project. I’m just trying to get the basics into my brain at the moment. That and I’ve been looking a bit a libraries for parsing xml in perl, but they’re just a bit out of reach right now.

Kernel Source as Your Screen Saver

gnukathryn — Thu, 10 Jan 2008 13:31:20 +0000

I came across this blog post in one of the feeds I read daily. I thought it was cool and I wanted to share. It’s a way to use the Phosphor screen saver that comes with xscreensaver to display a random bit of the Linux kernel source.

I have to admit, I don’t use a screen saver. They drive me nuts. My screen powers down after 1 minute. And I like it that way. But this is cool enough and novel enough that I might try it, at least for a few days.

The directions are written for a Debian based system, so I’ll have to play around a bit and see if I can get it to work with Fedora. But everything seems bog standard. It uses a small program the author wrote to display the contents of a random file in a directory (this will also help me out in some scripting I’m doing for mplayer).

It of course assumes that you do have the xscreensaver package and said package contains the Phosphor screensaver. It also assumes that you have the kernel source on your system as well. It’s also necessary to compile the author’s program (which should only be `make` and `make install`).

If I get this to work, I’ll definitely report back. I’ll also report back on Argument Shuffle.

Ruby

gnukathryn — Sun, 06 Jan 2008 11:56:55 +0000

It’s been suggested that I stop abusing bash. Hey. I do my best. I’m not a programmer. I highly doubt I’ll ever be one.

A friend sent me a link to an interactive online Ruby tutorial. It’s made by the same folks who wrote Why’s (Poignant) Guide to Ruby. I skimmed through the book a couple weeks ago after seeing it mentioned on a blog somewhere. I really liked the writing style. That same style comes through in the tutorial. If you can get me to laugh, then you’ll probably hold my attention.

I haven’t moved very far through the tutorial yet. But I’m liking what I see so far. We’ll see how it goes.