Difference between revisions of "Building Guest Systems"

Revision as of 01:47, 7 May 2008

Building a guest

There are three parts to the vserver ... build command. Each part is separate by --. The first part are generic vserver options, such as hostname, available IP-addresses, and context id. The second part is specific to the chosen build method (chosen using -m <method> in the first part). The third part is completely optional and only implemented for a few build methods. These are options passed directly to whatever application is used to build guest.

There are a lot of options not covered here (yet). Use vserver - build --help to see them all.

Building guests using the debootstrap build method

• Build a Debian lenny guest.

vserver vserver1 build -m debootstrap --hostname vserver1.mydomain.com --interface eth0:192.168.1.10/24 -- -d lenny

lenny can be replaced by e.g. etch for Debian etch, edgy for Ubuntu edgy, or sid for Debian sid. Anything your debootstrap version can handle will be fine.

Building guests using the yum build method

• Make sure that your host system already has yum installed, preferably one that has been patched to work better with chroots.

• Build a CentOS 5-based guest using a minimal set of packages.

vserver vserver2 build -m yum --hostname vserver2.mydomain.com --interface eth0:192.168.1.11/24 -- -d centos5

centos5 can be replaced by e.g. f8 for Fedora 8, or fc6 for Fedora 6.

• If you want to manage the packages inside the guest, you will have to install some package management program(s) as well as internalize the RPM database. This can be achieved by

vyum vserver2 -- install yum
vserver vserver2 pkgmgmt internalize

Internal package management means that commands such as rpm, yum and rpmbuild can be used from inside the guest, as opposed to requiring the host administrator to run vrpm or vyum. If you use rpmbuild, you'll need internal package management, or use --nodeps (but that's strongly discouraged).

• Depending on your host's/guest's distribution, you may also need to do

vserver vserver2 exec bash -c "rm -f /var/lib/rpm/__db*; rpm --rebuilddb"

This is required if every rpm operation, for example rpm -qa, complains about a database version mismatch.

Building guests using the template build method

A template is a file containing a complete guest filesystem. This can be a tar(1)ball, a cpio(1)-archive, or a dump(8). It can be compressed using either gzip or bzip2. Multiple templates can be used, to do e.g. guest-specific modifications.

• Build a guest using a single template named stage4-i686-20070905.tar.bz2 located in /vservers/.templates.

vserver vserver3 build -m template --hostname vserver3.mydomain.com --interface eth0:192.168.1.12/24 -- -d gentoo -t /vservers/.templates/stage4-i686-20070905.tar.bz2

OR

• Build a guest using multiple templates, one named stage4-i686-20070905.tar.bz2 and one named httpd.tar.bz2.

vserver vserver3 build -m template --hostname vserver3.mydomain.com --interface eth0:192.168.1.12/24 -- -d gentoo -t /vservers/.templates/stage4-i686-20070905.tar.bz2 -t /vservers/.templates/httpd.tar.bz2

Building guests using the rsync build method

The rsync build method can be used to move a guest from one system to another. It is preferable for most guest distributions if the source guest is stopped when you create a one based on it, but it's not strictly required.

• Build a guest by rsync'ing from vserver3 on host1.

RSYNC_RSH=ssh vserver vserver4 build -m rsync --hostname vserver4.mydomain.com --interface eth0:192.168.1.13/24 -- --source root@host1:/vservers/vserver3

OR

• Build a guest by rsync'ing from vserver1 on the same host.

vserver vserver4 build -m rsync --hostname vserver4.mydomain.com --interface eth0:192.168.1.13/24 -- --source vserver1

Building guests using the clone build method

The clone build method copies the filesystem from one guest to another, much like the rsync build method, but the thing that separates it is that it knows about unified/hashified files. This means that it only creates new links for such files, and copies the rest, which can lead to significantly speedier builds.

• Build a guest by using vserver4 as a reference.

vserver vserver5 build -m clone --hostname vserver5.mydomain.com --interface eth0:192.168.1.14/24 -- --source /vservers/vserver4

Post-build customization

Verifying guest functionality

• Once the guest is built, it's time to start it.

vserver vserverX start

• At this point, you can use both

vserver vserverX enter

and

vserver vserverX exec ...

to do things inside the guest.

• To stop it, simply use

vserver vserverX stop