Schadenfreude » sysadmin

Fill an LVM volume group completely with a single logical volume

Erik — Thu, 25 Aug 2011 21:29:52 +0000

I learned a cool LVM trick today – how to resize a logical volume to use a certain percentage of a volume group. Since I just have one logical volume in the group, I did the following:

[root@nyu ~]# lvextend -l +100%FREE /dev/diclonius/vector
  Extending logical volume vector to 7.28 TiB
  Logical volume vector successfully resized

Thanks Redhat Documentation!

In other news, I ran a performance test on my 5-drive RAID-5 using HD204UI drives from Samsung:

[root@nyu tmp]# dd if=/dev/zero of=foo count=5 bs=$((1024*1024*1024))
5+0 records in
5+0 records out
5368709120 bytes (5.4 GB) copied, 18.1434 s, 296 MB/s
[root@nyu tmp]# dd if=foo of=/dev/null
10485760+0 records in
10485760+0 records out
5368709120 bytes (5.4 GB) copied, 15.2682 s, 352 MB/s

So, 350MB/sec reads and 296MB/sec writes! Not bad!!

How to set the RTC max_user_freq in newer kernels

Erik — Mon, 20 Jul 2009 01:03:07 +0000

I found out today how to set the real time clock max frequencies in Ubuntu since they removed the possibility to do it from sysutil.conf from newer kernels. Add the following to your /etc/rc.local or another startup script:

echo 2048 >/sys/class/rtc/rtc0/max_user_freq
echo 2048 >/proc/sys/dev/hpet/max-user-freq

Reboot, and you should get better performance from things like mplayer.

0install: A package manager for the lusers

Erik — Thu, 19 Jul 2007 15:55:00 +0000

Zeroinstall is my new friend. It’s a package manager that’s decentralized, and can be used on machines where users need applications, but don’t know how to compile (or are unwilling to). Installing applications happens in the home directory, and once a program is run once, it is stored in the home directory for later use. All packages can be signed with GPG keys, and the packaging GUI is amazingly awesome.

Check out my 0install repository. You can run things like this:


sudo apt-get install zeroinstall-injector
0launch http://modzer0.cs.uaf.edu/repos/hank/0install/Processing.xml

There’s packages for all the popular distributions. Get it now! It’s awesome.

GNU Screen’s hardstatus

Erik — Sun, 15 Jul 2007 00:17:00 +0000

I use GNU Screen. A lot. I found an article linked from DIgg today that showed me how to use a setting called hardstatus to set the little bar at the bottom to my liking. I decided to mess around with it a bit, and I ended up with this:

It shows my hostname, IP, uptime, screen window number and name, date and time, and load averages. Pretty cool, huh?

This is how you do it:

First, create a .screenrc file and dump this in there:


hardstatus alwayslastline
backtick 1 60 60 /home/hank/.screen_hardstatus
hardstatus string "%{Gk}%H: %{+s y}%1` | %=%n: %t%= | %m/%d %c | %{+b}%l"

Now, see the line that starts with backtick? That tells screen what program to run for assigning output to %1` in the hardstatus string. Let’s make the .screen_hardstatus file as well (make it in your own home directory).


#!/bin/bash
# Script to get run by hardstatus in screen.
# Prints customized single-line system stats
IP=`ifconfig eth0 | grep Mask | cut -d: -f2 | cut -d " " -f1`
UPTIME=`perl -pe 's/^(\d+).*/sprintf("%d", ($1\/(24*3600)))." days"/e' /proc/uptime`
echo -n "$IP | Up: $UPTIME"

I cheated and used perl, but all of this could safely be converted to sed/awk easily. All this does is print my raw dotted quad IP address, a pipe, and then the current uptime in days rounded down.

Now, just run screen. You should see something similar to the first picture. I used this page a lot to customize the colors, etc.

Fixing .Xdefaults in Ubuntu

Erik — Thu, 26 Oct 2006 20:16:15 +0000

I have been having a problem getting .Xdefaults to be loaded in X. This
is a major issue for me since I like my fonts to be a certain size in aterm,
but I don’t want to hack up my runline in fluxbox to reflect all the custom
settings. Therefore, I have all my settings defined in the .Xdefaults
file. So, tonight, after I upgraded to Edgy Eft, I decided that this needed
to be fixed. After a quick google google I found that all I had to do was
run:


xrdb -merge ~/.Xdefaults

And all my problems were solved. A quick insert into .fluxbox/startup and
I was in business.

In other news, Edgy Eft Rocks. Just customized the default GDM theme so it
looks better. I think I might want to get a MacBook or a nice Powerbook G4
for my next laptop. Apparently, in Linux, you can make the touchpad act like
Synaptics with a driver hack to put it in raw mode. As far as I can tell,
this is merged in the newest Linux kernels. This allows for the kind of tap
clicking I like (1 finger for left button, 2 for middle, 3 for right), and
thanks to a broken left touchpad button on the Asus M6N I have, I’ve gotten
used to this style of clicking, and I like it now.

Do you have some Chage?

Erik — Mon, 14 Aug 2006 03:07:56 +0000

This makes it so the user has to change their password on login:


# chage -M 1 
# chage -d 1

Make sure to set -M back to normal afterwards


# chage -M 99999

This makes it so easy. Too bad it’s named like saying ”’change”’ with a cold…

Easy Global Change of CAPS to Ctrl in X

Erik — Thu, 10 Aug 2006 03:14:52 +0000

Thanks to this page, I found what I was looking for:


        Option          "XkbOptions"    "ctrl:nocaps"

Magical SVN Remove

Erik — Sun, 06 Aug 2006 15:37:52 +0000

Have you ever wanted to batch remove some Subversion files? Try this on for size:


svn rm `svn stat | grep ! | sed -e 's/^\!\s\+//;s/$/ /' | tr -d '\n'`

That will remove all the entries from svn stat that start with !. Very handy. Took a few minutes to write (sed wouldn’t get rid of my newline, so I used tr …), but it’s worth it.

Ubuntu Ruby Woes Crushed

Erik — Thu, 13 Jul 2006 22:01:03 +0000

I installed Ubuntu Dapper Drake on the ole’ laptop today, and needed ruby, but it wouldn’t compile correctly. Luckily, the internet saved me again. Here’s how to compile it without getting errors on Gem Setup