It is easy to do an in-place upgrade of Ubuntu Server from 8.10 ‘Intrepid Ibex‘ to 9.04 ‘Jaunty Jackalope‘. You can do this remotely over ssh or whatever you use to control your server. Best practices say to make sure to backup your server before doing the upgrade. I’ve done several servers this way with no issues!

Issue the command:

sudo apt-get update; sudo apt-get upgrade; sudo apt-get install update-manager-core; sudo do-release-upgrade

Follow any prompts to first upgrade the current distribution with the newest packages, then do the release upgrade.

I recently came across a typo that existed in a bunch of html files on my web server. I thought it should be easy enough to change, but since it was in a number of files, editing it by hand would be time consuming. Fortunately, there is an easy, one liner command to replace the text in multiple files in a sub directory using recursion.

grep -lr -e '<oldword>' * | xargs sed -i 's/<oldword>/<newword>/g'

This command broken down:

• grep for the word in a files, use recursion (to find files in sub directories), and list only file matches
• | xargs passes the results from the grep command to sed
• sed -i uses a regular expression (regex) to evaluate the change: s (search) / search word / target word / g (global replace)

For more information, see man pages for grep, sed, and xarg. Also it is very handy to learn about regular expressions as they are a valuable tool to any command line programmer!

As previously written on this blog, I have set up a display in our lobby at work to display the day’s current events and meetings using Ubuntu and a tiny PC. Since this is a display which is on all day, the screensaver and monitor blanking (and other Energy Star features) are all turned off.

Under the auspice of wanting to save energy and also extending the life of a new monitor, someone suggested that we turn off the monitor at night using an electrical timer. A lightbulb went off in my head, that there must be a better way to do this via command line and then run it in the cron.

It turns out the solution is very simple. The xset command is the X server preferences command. It has a simple command to turn off the monitor:

$ xset dpms force off

and to turn the monitor back on:

$ xset dpms force on

You can also check the status of the X server settings by using:

$ xset -q

Also, when dpms turns off the monitor, it will turn back on after a keypress or by moving the mouse. Since this is a lobby display, there is no keyboard or mouse installed in the system.

I’ve rolled this into a little bash script with on, off, and status switches:

#!/bin/bash
export DISPLAY=:0.0

if [ $# -eq 0 ]; then
  echo usage: $(basename $0) "on|off|status"
  exit 1
fi

if [ $1 = "off" ]; then
  echo -en "Turning monitor off..."
  xset dpms force off
  echo -en "done.\nCheck:"
  xset -q|grep "Monitor is"
elif [ $1 = "on" ]; then
  echo -en "Turning monitor on..."
  xset dpms force on
  echo -en "done.\nCheck:"
  xset -q|grep "Monitor is"
elif [ $1 = "status" ]; then
  xset -q|sed -ne 's/^[ ]*Monitor is //p'
else
  echo usage: $(basename $0) "on|off|status"
fi

You can then use cron to turn off the monitor at night, and back on in the morning:

0 20 0 0 0 /home/lobby/monitorControl.sh off
0 7 0 0 0 /home/lobby/monitorControl.sh on

This script will turn it off at 8pm and back on at 7am.

Note that this was written for an Ubuntu system, but the xset command is pretty generic so any system that runs Xserver like RedHat, CentOS, Debian, Fedora, etc should be able to use the script as well.

Running sudo apt-get upgrade, I started getting this error:

Reading package lists... Done

W: GPG error: http://ppa.launchpad.net intrepid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 313D312748A22A95

W: You may want to run apt-get update to correct these problems

Ah ha! But apt-get update is the command causing this problem.

The solution is to import this key from the gpg servers; I don’t know why this isn’t done automatically, but here is it:

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 313D312748A22A95; gpg --export --armor 313D312748A22A95 | sudo apt-key add -

Resulting in:

Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /etc/apt/secring.gpg --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --recv-keys --keyserver keyserver.ubuntu.com 313D312748A22A95
gpg: requesting key 48A22A95 from hkp server keyserver.ubuntu.com
gpg: key 48A22A95: public key "Launchpad PPA for Filip Brcic" imported
gpg: Total number processed: 1
gpg: unchanged: 1
OK

Congrats! sudo apt-get update now works properly!

Readers should note that this applies to Ubuntu 8.10 Intrepid Ibex only!

ZFS is a relatively new filesystem created by Sun. It is released under the CDDL License which is incompatible with Linux’s GPL License, meaning that it can not be installed natively in the kernel. Therefore, for not it is relegated to addon packages and is brought to Ubuntu via the Fuse framework.

For more information on this see the Ubuntu Wiki article on ZFS.

The wiki article also explains this, but getting ZFS installed on Ubuntu is actually pretty straightforward by issuing these commands:

$ sudo echo "deb http://ppa.launchpad.net/brcha/ubuntu intrepid main" >> /etc/apt/sources.list.d/zfs-fuse.list
$ sudo echo "deb-src http://ppa.launchpad.net/brcha/ubuntu intrepid main" >> /etc/apt/sources.list.d/zfs-fuse.list
$ sudo apt-get update
$ sudo apt-get install zfs-fuse

This installs zfs onto your system. Now to create your raid-z array! Its dead simple.

$ sudo zpool create media -m /storage raidz /dev/sda /dev/sdb /dev/sdc

In the above command:

• media is the name of the pool,
• /storage is the mount point (make sure it already exists),
• raidz is the type of mirroring/striping we are going to run (see more below), and
• the rest of the options are the devices you are adding into the pool.

Make sure the mount directory already exists.

The type of array you are creating can be the following:

• mirror will mirror the data across disks
• raidz will mirror and stripe data across all disks, allowing 1 drive to fail without losing data
• raidz2 will mirror and stripe data across all disks, allowing 2 drives to fail without losing data (but creating more overhead)

That really is it! You’ll then have a raid array, mounted to your indicated mount point. You can do all kinds of cool stuff with your pool, such as add disks, export the array to a file, import an exported file to the disk, create hot spares, and more.

After far as speed goes, I tested the pool performance with bonnie and also via real world estimates, and I’m only receiving about 20Mb/sec. Its not stellar and I plan to do some more testing as I haven’t tweaked my disks at all and I think I may be able to push it further. This slowness is caused by the checksumming that zfs does — it makes your data extremely safe but it does cause a lot of CPU overhead.

Hopefully ZFS will get more and more stable with time (although I haven’t had any problems with it so far!) and will be included in the Linux kernel, because it really is a great performing, easy to use file system. The uses for it could be tremendous, such as creating a desktop system as a zfs pool and creating instant disk backups from it with minimal overhead. Think: Time Machine for Linux!