#summary How to build a core-root filesystem template for use with CORE

= About OpenVZ and CORE OS templates =

OpenVZ uses [http://wiki.openvz.org/OS_template operating system templates] to supply the virtual containers with a root filesystem. "An OS template is basically a set of packages from some Linux distribution used to populate a container." (OpenVZ wiki) 

By default, CORE uses a single OS template cache for all of its nodes, located in `/vz/private/core-root`. This is a convenience so you can install a binary in one place and then use it on all nodes, and it saves a lot of disk space.

 * CORE nodes share the `/vz/private/core-root` filesystem through a symlink
{{{
# ls -al /vz/private
total 12
drwx------  3 root root 4096 Jun  9 11:03 .
drwxr-xr-x  8 root root 4096 Feb 18 14:39 ..
lrwxrwxrwx  1 root root   21 Jun  9 11:01 1000 -> /vz/private/core-root
lrwxrwxrwx  1 root root   21 Jun  9 11:01 1001 -> /vz/private/core-root
lrwxrwxrwx  1 root root   21 Jun  9 11:01 1002 -> /vz/private/core-root
drwxr-xr-x 20 root root 4096 Jun  1 09:33 core-root
}}}
 * each CORE node has its `/root` directory bind mounted to `/tmp/n0` (where `n0` corresponds to the node number)
 * some state directories are symlinked to this `/root` directory, allowing for per-node state
{{{
lrwxrwxrwx  1 root root    13 Jun  2 13:27 var/log -> /root/var/log
lrwxrwxrwx  1 root root    13 Jun  2 13:27 var/run -> /root/var/run
lrwxrwxrwx  1 root root 15 Jun  2 13:27 etc/quagga/Quagga.conf -> /root/boot.conf
}}}
 * you can create and destroy these symlinked containers with the `vzcreate.sh` and `vzdestroy.sh` scripts
 * you can create your own containers based off of other templates (e.g. one debian-5.0 and one suse-11.1) and CORE will try to use them as-is (container 1001 corresponds to n1, etc.)


= How to make a core-root template =
This is how the `core-root` template was made.

 # start with the precreated template *`centos-5-x86-devel.tar.gz`* available [http://download.openvz.org/template/precreated/centos-5-x86-devel.tar.gz here] (download this to your `/vz/template/cache` directory`, *don't unpack it!*)
 # create a container the normal OpenVZ way; this properly sets up devices nodes, etc.
{{{
vzctl create 101 --ostemplate centos-5-x86-devel --config core
}}}
 # start and enter the container, turn off unnecessary services
{{{
vzctl start 101
vzctl enter 101
chkconfig --list | grep 5:on
for i in iptables lm_sensors mcstrans netfs portmap restorecond sendmail sshd; do chkconfig $i off; done
}}}
 # more steps here...

= How to make the core-root RPM =