Editing Ubuntu Gutsy template creation

[[Category: HOWTO]]
[[Category: Templates]]
[[Category: Ubuntu]]
This article summarizes the experience of creating Ubunty Gutsy Gibbon (a.k.a. 7.10) template for OpenVZ.

Template creation is based on debootstrap, and the procedure is similar to [[Debian template creation]], but it differs in some subtle details.

== Prerequisites ==

=== debootstrap ===
You have to have a <code>debootstrap</code> working for Gutsy, i.e. you should have
* <code>debootstrap</code> and its dependencies
* <code>/usr/lib/debootstrap/scripts/gutsy</code> file

The simplest way to have it all is to work on an Ubuntu Gutsy system (be it on a real machine or inside a container). If you don't have <code>debootstrap</code> installed, this is the command to install it:

 # apt-get install debootstrap

On a Gentoo Linux, <code>debootstrap</code> is also available, this is how you can install it:

 # emerge \>=debootstrap-1.0.0

Possible you will first need to add it to package.keywords.

On a Fedora system (at least Fedora 8, not sure about earlier versions):

 # yum install debootstrap

=== vzctl ===

You need vzctl-3.0.22 or later to work with Ubuntu Gutsy Gibbon. If vzctl-3.0.18 or earlier is used, you will not be able to run your Ubuntu Gutsy container. See {{bug|662}} for details.

Note: Older versions of vzctl are working if you install <code>sysvinit</code> (which will remove <code>upstart</code>). The only problem I had was the network did not start, so I added "/etc/init.d/networking restart" to /etc/re.local.

== Creating template ==

=== Running debootstrap ===

Create a working directory:

 [HW]# mkdir gutsy-chroot

Run debootstrap to install a minimal Ubunty Gutsy system into that directory:

 [HW]# debootstrap [--arch ''ARCH''] gutsy gutsy-chroot 

If ARCH of CT0 is equal to container, you can skip the --arch option, but if you need to build an OS template for another ''ARCH'', specify it explicitly:
* for AMD64/x86_64, use <code>amd64</code>
* for IA64, use <code>ia64</code>
* for i386 <code>i386</code>

=== Preparing/starting a container ===

Now then you have an installation created by <code>debootstrap</code>, you can run it as a container. In the example below CT ID of 777 is used; of course you can use any other non-allocated ID.

{{Note|an alternative way is using chroot instead of running a container. This is not recommended because of security concerns.}}

==== Moving installation to container private area ====

You should move the contents of gutsy-chroot directory into new container private area, like this:

 # mv gutsy-chroot /vz/private/777

==== Setting container config ====
An initial config for the [[container]] is needed:
 # vzctl set 777 --applyconfig vps.basic --save

==== Setting container OSTEMPLATE ====
Also, we need <code>OSTEMPLATE</code> to be set in container configuration file, for the [[vzctl]] to work properly.

 # echo "OSTEMPLATE=ubuntu-7.10" >> /etc/vz/conf/777.conf

==== Setting container IP address ====
For the [[container]] to be able to download updates from the Internet, we need a valid IP address for it:
 # vzctl set 777 --ipadd x.x.x.x --save

{{Note|if you use private IP for the container, you have to set up NAT as described in [[Using NAT for container with private IPs]].}}

==== Setting DNS server for the container ====
For the [[container]] to be able to download updates from the Internet, we also need to specify a DNS for it:
 # vzctl set 777 --nameserver x.x.x.x --save

Instead of <code>x.x.x.x</code>, specify the same IP that you have in your <code>/etc/resolv.conf</code>.

==== Starting container ====
Now start the container:
 # vzctl start 777

=== Modify the installation ===

You have to do some things in order to modify the installation to better suit the environment it will be run in (i.e. a container).

First, enter a container:
 # vzctl enter 777

{{Warning|Do not run the commands below on the hardware node, they are only to be run within the container!}}
==== Remove unneeded packages ====

Some packages does not make sense in a container, or are really optional. Remove those:

 [container]# dpkg -P ubuntu-minimal wpasupplicant wireless-tools \
   udev pcmciautils initramfs-tools volumeid console-setup \
   xkb-data usbutils mii-diag alsa-base alsa-utils ethtool \
   module-init-tools linux-sound-base console-tools \
   console-terminus busybox-initramfs libvolume-id0 \
   ntpdate eject libasound2 pciutils tasksel tasksel-data \
   laptop-detect

{{Note|On removing the deb-package "module-init-tools", a fake-modprobe is needed for IPv6 addresses, see below!}}

Note that the above list of packages may be too extensive. Say, if you want to use <code>tasksel</code> tool, do not remove it — but then you have to let laptop-detect stay.

Clean up after udev:

 [container]# rm -fr /lib/udev

==== Disable getty ====
On a usual Linux system, <code>getty</code> is running on a virtual terminals, which a container does not have. So, having <code>getty</code> running doesn't make sense; more to say, it complains it can not open terminal device and this clutters the logs.

So, first of all we stop all <code>getty</code> processes:

 [container]# initctl stop tty{1,2,3,4,5,6}

Next, we disable running <code>getty</code>. This can be done in two ways:

First way:
 [container]# rm /etc/event.d/tty*

Second way:
 [container]# dpkg -P system-services

Second way can be dangerous for future versions of <code>system-services</code>, but it's OK for now since the only service they carry is running <code>getty</code>s.

====  Set sane permissions for /root directory ====

 [container]# chmod 700 /root

==== Disable root login ====

 [container]# usermod -L root

==== "fake-modprobe" needed for IPv6 addresses ====

 [container]# ln -s /bin/true /sbin/modprobe

<small>On setup IPv6, the command "modprobe -Q IPv6" is called, which fails without the "fake-modprobe"</small>

==== Get new security updates ====

 [container]# apt-get update && apt-get upgrade

<small>This didn't show anything for me, but might do something in the future.</small>

==== Install some more packages ====

 [container]# apt-get install ssh quota

Feel free to add packages which you want to have in a default template to this command.

==== Fix SSH host keys ====
This is only useful if you installed SSH above.  Each individual [[container]] should have its own pair of SSH host keys.  The code below will wipe out the existing SSH keys and instruct the newly-created [[container]] to create new SSH keys on first boot.

<!-- please DO NOT remove <pre>...</pre> pair of tags below,
     otherwise quotes after -N (-N '') are not visible -->
<pre>
rm -f /etc/ssh/ssh_host_*
cat << EOF > /etc/rc2.d/S15ssh_gen_host_keys
#!/bin/sh
ssh-keygen -f /etc/ssh/ssh_host_rsa_key -t rsa -N ''
ssh-keygen -f /etc/ssh/ssh_host_dsa_key -t dsa -N ''
rm -f \$0
EOF
chmod a+x /etc/rc2.d/S15ssh_gen_host_keys
</pre>

==== Disable <code>sync()</code> for syslog ====

Turn off doing <tt>sync()</tt> on every write for <code>syslog</code>'s log files, to improve overall I/O performance.
In Ubuntu this is already done for most log files and levels, so you can omit this step if you know what you are doing.

<!-- DO NOT remove <pre> here, it's useful -->
 <pre>[container]# sed -i -e 's@\([[:space:]]\)\(/var/log/\)@\1-\2@' /etc/syslog.conf</pre>

==== Fix <code>/etc/mtab</code> ====
Link <code>/etc/mtab</code> to <code>/proc/mounts</code>, so <code>df</code> and friends will work:
 [container]# rm -f /etc/mtab
 [container]# ln -s /proc/mounts /etc/mtab

After that, it would make sense to disable <code>mtab.sh</code> script which messes with <code>/etc/mtab</code>:
 [container]# update-rc.d -f mtab.sh remove

==== Disable some services ====

In most of the cases you don't want klogd to run -- the only exception is if you configure iptables to log some events -- so you can disable it:

 [container]# update-rc.d -f klogd remove

==== Hostname ====
Set proper hostname:
 [container]# echo "localhost" > /etc/hostname

==== Set /etc/hosts ====

 [container]# echo "127.0.0.1 localhost.localdomain localhost" > /etc/hosts

==== Add ptys to /dev ====

This is needed in case /dev/pts will not me mounted after container start. In case /dev/ttyp* and /dev/ptyp* files are present, and LEGACY_PTYS support is enabled in the kernel, vzctl will still be able to enter container.

 [container]# cd /dev && /sbin/MAKEDEV ptyp

==== Remove nameserver(s) ====

Remove DNS entries:
 [container]# > /etc/resolv.conf

==== Clean packages ====
After installing packages, you'll have some junk packages laying around in your cache.  Since you don't want your template to have those, this command will wipe them out.
 [container]# apt-get clean

==== Cleaning up log files ====

 [container]# cd /var/log
 [container]# > messages; > auth.log; > kern.log; > bootstrap.log
 [container]# > dpkg.log; > syslog; > daemon.log; > apt/term.log
 [container]# rm -f *.0 *.1

==== Anything else? ====

Think of what else could be done to better suit your needs.

==== Exit from the container ====

Now everything is done.  Exit from the template and go back to the hardware node.

 [container]# exit

== Preparing for and packing template cache ==

The following commands are to be run in the host system (i.e. not inside a container).

We don't need an IP for the container anymore, and we definitely do not need it in template cache, so remove it:
 [HW]# vzctl set 777 --ipdel all --save

Stop the container:
 [HW]# vzctl stop 777

Change dir to the container private:
 [HW]# cd /vz/private/777

Now create a cached OS tarball.  In the command below, you'll want to replace <arch> with your architecture (i386, amd64, ia64, etc). '''Note the space and the dot at the end of the command'''.
 [HW]# tar --numeric-owner -czf /vz/template/cache/ubuntu-7.10-<arch>-minimal.tar.gz .

Look at the resulting tarball to see its size is sane:
 # ls -lh /vz/template/cache
 -rw-r--r-- 1 root root   53M Nov 15 12:40 ubuntu-7.10-i386-minimal.tar.gz

== Testing template cache ==
We can now create a container based on the just-created template cache.  Be sure to change <tt>i386</tt> to your architecture just like you did when you named the tarball above.
 [HW]# vzctl create 123456 --ostemplate ubuntu-7.10-<arch>-minimal

Now make sure that your new container it works:
 [HW]# vzctl start 123456
 [HW]# vzctl exec 123456 ps axf

You should see that a few processes are running.

Other tests that could be done are:
 [HW]# vzctl enter 123456
 [container]# ps axf
 [container]# mount
 [container]# dpkg -l
 [container]# logout
 [HW]#

Feel free to do more tests.

== Final cleanup ==
Stop and remove the test container you just created:
 [HW]# vzctl stop 123456
 [HW]# vzctl destroy 123456
 [HW]# rm -f /etc/vz/conf/123456.conf.destroyed

Finally, let's remove the container we used for OS template cache creation:
 [HW]# vzctl destroy 777
 [HW]# rm -f /etc/vz/conf/777.conf.destroyed

== Updating the template cache ==

See [[Updating Ubuntu template]]