Synnefo » Ganeti Instance Image

ganeti-instance-debootstrap

===========================

This is a guest OS definition for Ganeti (http://code.google.com/p/ganeti).

It will install a minimal version of Debian or Ubuntu via debootstrap (thus it

requires network access). This only works if you have a Debian-based node or

you have debootstrap installed by hand on another distribution.

Installation

------------

In order to install this package from source, you need to determine what

options ganeti itself has been configured with. If ganeti was built

directly from source, then the only place it looks for OS definitions is

``/srv/ganeti/os``, and you need to install the OS under it::

  ./configure --prefix=/usr --localstatedir=/var \

    --sysconfdir=/etc \

    --with-os-dir=/srv/ganeti/os

  make && make install

If ganeti was installed from a package, its default OS path should

already include /usr/share/ganeti/os, so you can just run::

  ./configure -prefix=/usr --localstatedir=/var \

    --sysconfdir=/etc

  make && make install

Note that you need to repeat this procedure on all nodes of the cluster.

The actual path that ganeti has been installed with can be determined by

looking for a file named _autoconf.py under a ganeti directory in the

python modules tree (e.g.

``/usr/lib/python2.4/site-packages/ganeti/_autoconf.py``). In this file,

a variable named OS_SEARCH_PATH will list all the directories in which

ganeti will look for OS definitions.

Configuration of instance creation

----------------------------------

The kind of instance created can be customized via a settings file. This

file is not installed by default, as the instance creation will work

without it. The creation scripts will look for it in

``$sysconfdir/default/ganeti-instance-debootstrap``, so if you have run

configure with the parameter ``--sysconfdir=/etc``, the final filename

will be ``/etc/default/ganeti-instance-debootstrap``.

The following settings will be examined in this file (see also the file

named 'defaults' in the source distribution for more details):

- PROXY: http proxy to use for non-cached installs

- MIRROR: the mirror to use if not the default one

- ARCH: either i386 or amd64, otherwise your current architecture will

  be used

- SUITE: the actual OS to be installed; the current default is Debian

  *lenny*, and you can choose any of the OSes supported deboostrap (on

  Debian, look into /usr/share/deboostrap/scripts)

- EXTRAPKGS: most OSes will need some extra packages installed to make

  them work nicely under Xen; the example file containts a few

  suggestions

- CUSTOMIZE_DIR: a directory containing customization script for the instance.

  (by default $sysconfdir/ganeti/instance-debootstrap.d) See "Customization of

  the instance" below.

- GENERATE_CACHE: if 'yes' (the default), the installation process will

  save and reuse a cache file to speed reinstalls (located under

  $localstatedir/cache/ganeti-instance-debootstrap)

- CLEAN_CACHE: if empty, the cached files will never be cleaned and thus

  the installation will definitely need to be updated after install;

  otherwise, the value of this variable will be taken as the number of

  days after which to remove the cache file; the default is 14 (two

  weeks)

- PARTITION_STYLE: if 'none' the device will be formatted directly, if 'msdos'

  a partition table will be installed on it. You need to have kpartx installed

  to use the 'msdos' option. The default is 'msdos' from Ganeti 2.0 onwards,

  but still 'none' if installing under Ganeti 1.2

Note that the settings file is important on the node that the instance

is installed on, not the cluster master. This is indeed not a very good

model of using this OS but currently the OS interface in ganeti is

limiting.

Customization of the instance

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If run-parts is in the os create script, and the CUSTOMIZE_DIR (by default

$sysconfdir/ganeti/instance-debootstrap.d, /etc/ganeti/instance-debootstrap.d

if you configured the os with --sysconfdir=/etc) directory exists any

executable whose name matches the run-parts execution rules (quoting

run-parts(8): the  names  must consist entirely of upper and lower case

letters, digits, underscores, and hyphens) is executed to allow further

personalization of the installation. The following environment variables are

passed, in addition to the ones ganeti passes to the OS scripts:

TARGET: directory in which the filesystem is mounted

SUITE: suite installed by debootstrap (eg: lenny)

ARCH: target architecture

PARTITION_STYLE: style of the disk partitioning (see above)

EXTRA_PKGS: extra packages installed by debootstrap

BLOCKDEV: ganeti block device

FSYSDEV: device in which the filesystem resides (the one mounted in TARGET)

The scripts in CUSTOMIZE_DIR can exit with an error code to signal an error in

the instance creation, should they fail.

The scripts in CUSTOMIZE_DIR should not start any long-term processes or

daemons using this directory, otherwise the installation will fail because it

won't be able to umount the filesystem from the directory, and hand the

instance back to Ganeti.

Caching

~~~~~~~

As described above, the install process uses a cache file in order to

speed up repeated installs. If you only rarely do installs, this will

not matter to you, but if you want to install 10 instances in a row, the

difference will be visible.

The default settings are to generate a cache, and to clean it up after

two weeks.

Note that the cache will use one file per architecture per suite, so if

you install multiple suites there might be a non-trivial amount of space

used in the cache directory. It is safe to remove manually the files.

It is also possible, if done with care, to modify and regenerate the

cache file (which is simply a tar archive) in order to preseed your

installs with site-specific customizations.

Instance notes

--------------

The instance is a minimal install:

 - it has no password for root; simply login at the console

 - it has no network interfaces defined (besides lo); add your own

   definitions to /etc/network/interfaces

 - after configuring the network, it is recommended to run ``apt-get

   update`` so that signatures for the release files are picked up