Ubuntu Manpage: ganeti-os-interface - Specifications for guest OS types

Name

       ganeti-os-interface - Specifications for guest OS types

DESCRIPTION

       The  method  of supporting guest operating systems in Ganeti is to have, for each guest OS
       type, a directory containing a number of required files.  This directory must  be  present
       across all nodes (Ganeti doesn't replicate it) in order for the OS to be usable by Ganeti.

REFERENCE

There are eight required files: create, import, export, rename, verify (executables),
ganeti_api_version, variants.list and parameters.list (text files).

Common environment
All commands will get their input via environment variables. A common set of variables
will be exported for all commands, and some of them might have extra ones. Note that all
counts are zero-based.

Since Ganeti version 2.5, the environment will be cleaned up before being passed to
scripts, therefore they will not inherit the environment in with which the ganeti node
daemon was started. If you depend on any environment variables (non-Ganeti), then you
will need to define or source them appropriately.

OS_API_VERSION
The OS API version that the rest of the environment conforms to.

INSTANCE_NAME
The instance name the script should operate on.

INSTANCE_OS, OS_NAME
Both names point to the name of the instance's OS as Ganeti knows it. This can
simplify the OS scripts by providing the same scripts under multiple names, and
then the scripts can use this name to alter their behaviour.

With OS API 15 changing the script behavior based on this variable is deprecated:
OS_VARIANT should be used instead (see below).

OS_VARIANT
The variant of the OS which should be installed. Each OS must support all variants
listed under its variants.list file, and may support more. Any more supported
variants should be properly documented in the per-OS documentation.

HYPERVISOR
The hypervisor of this instance.

DISK_COUNT
The number of disks the instance has. The actual disk definitions are in a set of
additional variables. The instance's disk will be numbered from 0 to this value
minus one.

DISK_%N_PATH
The path to the storage for disk N of the instance. This might be either a block
device or a regular file, in which case the OS scripts should use losetup (if they
need to mount it). E.g. the first disk of the instance might be exported as
DISK_0_PATH=/dev/drbd0.

DISK_%N_ACCESS
This is how the hypervisor will export the instance disks: either read-write (rw)
or read-only (ro).

DISK_%N_UUID
The uuid associated with the N-th disk of the instance.

DISK_%N_NAME
(Optional) The name, if any, associated with the N-th disk of the instance.

DISK_%N_FRONTEND_TYPE
(Optional) If applicable to the current hypervisor type: the type of the device
exported by the hypervisor. For example, the Xen HVM hypervisor can export disks
as either paravirtual or ioemu.

DISK_%N_BACKEND_TYPE
How files are visible on the node side. This can be either block (when using block
devices) or file:type, where type is either loop, blktap or blktap2, depending on
how the hypervisor will be configured. Note that not all backend types apply to
all hypervisors.

NIC_COUNT
Similar to the DISK_COUNT, this represents the number of NICs of the instance.

NIC_%N_MAC
The MAC address associated with this interface.

NIC_%N_UUID
The uuid associated with the N-th NIC of the instance.

NIC_%N_NAME
(Optional) The name, if any, associated with the N-th NIC of the instance.

NIC_%N_IP
The IP address, if any, associated with the N-th NIC of the instance.

NIC_%N_MODE
The NIC mode, routed, bridged or openvswitch

NIC_%N_BRIDGE
The bridge to which this NIC will be attached. This variable is defined only when
the NIC is in bridged mode.

NIC_%N_LINK
In bridged or openvswitch mode, this is the interface to which the NIC will be
attached (same as NIC_%N_BRIDGE for bridged). In routed mode it is the routing
table which will be used by the hypervisor to insert the appropriate routes.

NIC_%N_FRONTEND_TYPE
(Optional) If applicable, the type of the exported NIC to the instance, this can be
one of: rtl8139, ne2k_pci, ne2k_isa, paravirtual.

NIC_%d_NETWORK_NAME
(Optional) If a NIC network is specified, the network's name.

NIC_%d_NETWORK_UUID
(Optional) If a NIC network is specified, the network's uuid.

NIC_%d_NETWORK_FAMILY
(Optional) If a NIC network is specified, the network's family.

NIC_%d_NETWORK_SUBNET
(Optional) If a NIC network is specified, the network's IPv4 subnet.

NIC_%d_NETWORK_GATEWAY
(Optional) If a NIC network is specified, the network's IPv4 gateway.

NIC_%d_NETWORK_SUBNET6
(Optional) If a NIC network is specified, the network's IPv6 subnet.

NIC_%d_NETWORK_GATEWAY6
(Optional) If a NIC network is specified, the network's IPv6 gateway.

NIC_%d_NETWORK_MAC_PREFIX
(Optional) If a NIC network is specified, the network's mac prefix.

NIC_%d_NETWORK_TAGS
(Optional) If a NIC network is specified, the network's tags, space separated.

OSP_name
Each OS parameter (see below) will be exported in its own variable, prefixed with
OSP_, and upper-cased. For example, a dhcp parameter will be exported as OSP_DHCP.

DEBUG_LEVEL
If non-zero, this should cause the OS script to generate verbose logs of its
execution, for troubleshooting purposes. Currently only 0 and 1 are valid values.

EXECUTABLE SCRIPTS

create
The create command is used for creating a new instance from scratch. It has no additional
environment variables bside the common ones.

The INSTANCE_NAME variable denotes the name of the instance, which is guaranteed to
resolve to an IP address. The create script should configure the instance according to
this name. It can configure the IP statically or not, depending on the deployment
environment.

The INSTANCE_REINSTALL variable is set to 1 when this create request is reinstalling an
existing instance, rather than creating a new one. This can be used, for example, to
preserve some data in the old instance in an OS-specific way.

export
This command is used in order to make a backup of a given disk of the instance. The
command should write to stdout a dump of the given block device. The output of this
program will be passed during restore to the import command.

The specific disk to backup is denoted by two additional environment variables:
EXPORT_INDEX which denotes the index in the instance disks structure (and could be used
for example to skip the second disk if not needed for backup) and EXPORT_DEVICE which has
the same value as DISK_N_PATH but is duplicated here for easier usage by shell scripts
(rather than parse the DISK_... variables).

To provide the user with an estimate on how long the export will take, a predicted size
can be written to the file descriptor passed in the variable EXP_SIZE_FD. The value is in
bytes and must be terminated by a newline character (\n). Older versions of Ganeti don't
support this feature, hence the variable should be checked before use. Example:

if test -n "$EXP_SIZE_FD"; then
blockdev --getsize64 $blockdev >&$EXP_SIZE_FD
fi

import
The import command is used for restoring an instance from a backup as done by export. The
arguments are the similar to those passed to export, whose output will be provided on
stdin.

The difference in variables is that the current disk is denoted by IMPORT_DEVICE and
IMPORT_INDEX (instead of EXPORT_...).

rename
This command is used in order to perform a rename at the instance OS level, after the
instance has been renamed in Ganeti. The command should do whatever steps are required to
ensure that the instance is updated to use the new name, if the operating system supports
it.

Note that it is acceptable for the rename script to do nothing at all, however be warned
that in this case, there will be a desynchronization between what gnt-instance list shows
you and the actual hostname of the instance.

The script will be passed one additional environment variable called OLD_INSTANCE_NAME
which holds the old instance name. The INSTANCE_NAME variable holds the new instance
name.

A very simple rename script should at least change the hostname and IP address of the
instance, leaving the administrator to update the other services.

verify
The verify script is used to verify consistency of the OS parameters (see below). The
command should take one or more arguments denoting what checks should be performed, and
return a proper exit code depending on whether the validation failed or succeeded.

Currently (API version 20), only one parameter is supported: parameters. This should
validate the OSP_ variables from the environment, and output diagnostic messages in case
the validation fails.

For the dhcp parameter given as example above, a verification script could be:

#!/bin/sh

case $OSP_DHCP in
""|yes|no)
;;
*)
echo "Invalid value '$OSP_DHCP' for the dhcp parameter" 1>&2
exit 1;
;;
esac

exit 0

TEXT FILES

   ganeti_api_version
       The ganeti_api_version file is a plain text file containing the version(s) of the guest OS
       API that this OS definition complies with, one per line.  The version documented  by  this
       man page is 20, so this file must contain the number 20 followed by a newline if only this
       version is supported.  A script compatible  with  more  than  one  Ganeti  version  should
       contain  the most recent version first (i.e.  20), followed by the old version(s) (in this
       case 15 and/or 10).

   variants.list
       variants.list is a plain text file containing all the declared supported variants for this
       OS,  one  per  line.  If this file is missing or empty, then the OS won't be considered to
       support variants.

       Empty lines and lines starting with a hash (#) are ignored.

   parameters.list
       This file declares the parameters supported by the OS, one parameter per line,  with  name
       and description (space and/or tab separated).  For example:

              dhcp Whether to enable (yes) or disable (no) dhcp
              root_size The size of the root partition, in GiB

       The parameters can then be used in instance add or modification, as follows:

              # gnt-instance add -O dhcp=no,root_size=8 ...

NOTES

Backwards compatibility
Ganeti 2.3 and up is compatible with API versions 10, 15 and 20. The OS parameters and
related scripts (verify) are only supported in version 20. The variants functionality
(variants.list, and OS_VARIANT env. var) are supported/present only in version 15 and up.

Common behaviour
All the scripts should display an usage message when called with a wrong number of
arguments or when the first argument is -h or --help.

Upgrading from old versions
Version 15 to 20
The parameters.list file and verify script have been added. For no parameters, an empty
parameters file and an empty verify script which returns success can be used.

Version 10 to 15
The variants.list file has been added, so OSes should support at least one variant,
declaring it in that file and must be prepared to parse the OS_VARIANT environment
variable. OSes are free to support more variants than just the declared ones. Note that
this file is optional; without it, the variants functionality is disabled.

Version 5 to 10
The method for passing data has changed from command line options to environment
variables, so scripts should be modified to use these. For an example of how this can be
done in a way compatible with both versions, feel free to look at the debootstrap
instance's common.sh auxiliary script.

Also, instances can have now a variable number of disks, not only two, and a variable
number of NICs (instead of fixed one), so the scripts should deal with this. The biggest
change is in the import/export, which are called once per disk, instead of once per
instance.

Version 4 to 5
The rename script has been added. If you don't want to do any changes on the instances
after a rename, you can migrate the OS definition to version 5 by creating the rename
script simply as: