Editing Gentoo template creation

This page is about making a template cache for OpenVZ container from Gentoo Linux. The method is basically the same as described in [[Slackware template creation]] article.

== Download stage3 ==

We will make the template from a stage3 file. An OpenVZ OS template should be an archive (.tar.gz) of the root of a working system, but without the kernel and some files. You can download stage3 from the nearest mirror here: http://www.gentoo.org/main/en/mirrors.xml.

== Create directory for the new container and unarchive stage3 ==

<pre>
mkdir /vz/private/777
tar -xjf /root/stage3-i686-2008.0_beta2.tar.bz2 -C /vz/private/777
</pre>

== Create CT config ==
Now you need to create the configuration file for the container, 777.conf: 

<pre>
vzctl set 777 --applyconfig vps.basic --save
</pre>

== Edit CT config ==

Add the following to <code>/etc/vz/conf/777.conf</code>:
<pre>
OSTEMPLATE="gentoo"
</pre>

== Make /etc/mtab a symlink to /proc/mounts ==
The container's root filesystem is mounted by the host system, not the guest — and therefore root fs will not appear in <code>/etc/mtab</code>. It will lead to a non-working <code>df</code> command. To fix, link /etc/mtab to /proc/mounts.
<pre>
rm -f /vz/private/777/etc/mtab
ln -s /proc/mounts /vz/private/777/etc/mtab
</pre>
After replacing <code>/etc/mtab</code> with a symlink to <code>/proc/mounts</code>, you will always have up-to-date information of what is mounted in <code>/etc/mtab</code>.

== Replace /etc/fstab ==

<pre>
echo "proc /proc proc defaults 0 0" > /vz/private/777/etc/fstab
</pre>

We need only <code>/proc</code> to be mounted at boot time.

== Edit /etc/inittab ==

Edit <code>/vz/private/777/etc/inittab</code> and put a hash mark (#) at the beginning of the lines containing:

<pre>c?:1235:respawn:/sbin/agetty 38400 tty? linux</pre>

This prevents <code>getty</code> and login from starting on ttys that do not exist in containers.

== Edit /etc/shadow ==

Edit <code>/vz/private/777/etc/shadow</code> and change root's password in the first line to an exclamation mark (!): 

<pre>root:!:10071:0:::::</pre>

This will disable root login until the password is changed with <code>vzctl set CTID --userpasswd root:password</code>.

== Disable unneeded init scripts ==

The checkroot and consolefont init scripts should not be started inside containers:

<pre>
rm /vz/private/777/etc/runlevels/boot/checkroot
rm /vz/private/777/etc/runlevels/boot/consolefont
</pre>

== Edit /sbin/rc ==

Edit <code>/vz/private/777/sbin/rc</code> and put a hash mark (#) at the beginning of line 244 (your line number may be different):

<pre># try mount -n ${mntcmd:--t sysfs sysfs /sys -o noexec,nosuid,nodev}</pre>

This prevents the container from attempting to mount <code>/sys</code>.

To ensure that this change isn't automatically overwritten on update, add the following to <code>/vz/private/777/etc/make.conf</code>:

<pre>CONFIG_PROTECT="/sbin/rc"</pre>

== Set up udev ==

Using udev you will have problems since some devices nodes are not created.
For example sshd will fail to start since /dev/random and /dev/urandom are missing.
So it's recommended to disable udev.
Edit <code>/vz/private/777/etc/conf.d/rc</code> and change the <code>RC_DEVICES</code> line to:
<pre>
RC_DEVICES="static"
</pre>


If you want to enable udev read on.

Create some device nodes needed to enter a container:

<pre>
cd /vz/private/777/lib
mknod udev/devices/ttyp0 c 3 0
mknod udev/devices/ptyp0 c 2 0
mknod udev/devices/ptmx c 5 2
</pre>

Edit <code>/vz/private/777/etc/conf.d/rc</code> and change the <code>RC_DEVICES</code> and <code>RC_DEVICE_TARBALL</code> lines to:

<pre>
RC_DEVICES="udev"
RC_DEVICE_TARBALL="no"
</pre>

You have to leave the directory you are in for the next step to be OK, otherwise you will get this error message:
 vzquota : (error) Quota on syscall for 777: Device or resource busy
 vzquota on failed [3]

<pre>
cd /
</pre>

== Test ==

<pre>
vzctl start 777
vzctl enter 777
</pre>

You can check running services:

<pre>
rc-status -a
</pre>

All services in boot and default runlevels must be started. If everything all right, stop the container:

<pre>
vzctl stop 777
</pre>

== Making distfiles and portage tree of the host system available in a container ==

{{Warning|This step is optional and will result in shared files between containers! These steps can save space on disk but trade isolation and security... consider your options carefully!}}

To install software into a container with portage, you should mount <code>/usr/portage</code> into the container with the "bind" option. Do the following on the host after the container is started:

<pre>
mkdir /vz/root/777/usr/portage
mount -o bind /usr/portage /vz/root/777/usr/portage
</pre>

If your <code>/usr/portage/distfiles</code> directory resides on a different partition than your <code>/usr/portage</code> directory, do the following:

<pre>
mount -n -o bind /usr/portage/distfiles /vz/root/777/usr/portage/distfiles
</pre>

Now, to install a package into a container, you just need to enter the container using <code>vzctl enter</code> and run

<pre>
emerge package_name
</pre>

while you have all the needed files in the <code>/usr/portage/distfiles</code> of host system.

For security reasons, you should have these directories mounted only while installing software into a container.

{{Note|you have to <code>umount /vz/root/777/usr/portage/distfiles</code> before trying to stop your container.}}

== Create the template cache file ==

<pre>
cd /vz/private/777/
tar --numeric-owner -czf /vz/template/cache/gentoo.tar.gz *
</pre>

== Test the new template cache file ==

Create a new container from the template file:

<pre>
vzctl create 800 --ostemplate gentoo --ipadd 192.168.0.10 --hostname testvps
</pre>

If the container was created successfully, try to start it: 

<pre>
vzctl start 800
</pre>

If it started, and you can enter it using 

<pre>
vzctl enter 800
</pre>

congratulations, you've got a working Gentoo template!

Next you should set up the container's network, install portage snapshot (if you didn't setup mounted access on host's portage tree above) and emerge ssh then to enter the created container over SSH.

[[Category: HOWTO]]
[[Category: Templates]]
[[Category: Gentoo]]