1 ganeti-os-interface(7) Ganeti | Version @GANETI_VERSION@
2 ========================================================
7 ganeti-os-interface - Specifications for guest OS types
12 The method of supporting guest operating systems in Ganeti is to have,
13 for each guest OS type, a directory containing a number of required
14 files. This directory must be present across all nodes (Ganeti doesn't
15 replicate it) in order for the OS to be usable by Ganeti.
21 There are eight required files: *create*, *import*, *export*, *rename*,
22 *verify* (executables), *ganeti_api_version*, *variants.list* and
23 *parameters.list* (text files).
28 All commands will get their input via environment variables. A
29 common set of variables will be exported for all commands, and some
30 of them might have extra ones. Note that all counts are
33 Since Ganeti version 2.5, the environment will be cleaned up before
34 being passed to scripts, therefore they will not inherit the environment
35 in with which the ganeti node daemon was started. If you depend on any
36 environment variables (non-Ganeti), then you will need to define or
37 source them appropriately.
40 The OS API version that the rest of the environment conforms to.
43 The instance name the script should operate on.
46 Both names point to the name of the instance's OS as Ganeti knows
47 it. This can simplify the OS scripts by providing the same scripts
48 under multiple names, and then the scripts can use this name to
49 alter their behaviour.
51 With OS API 15 changing the script behavior based on this variable
52 is deprecated: OS_VARIANT should be used instead (see below).
55 The variant of the OS which should be installed. Each OS must
56 support all variants listed under its variants.list file, and may
57 support more. Any more supported variants should be properly
58 documented in the per-OS documentation.
61 The hypervisor of this instance.
64 The number of disks the instance has. The actual disk defitions are
65 in a set of additional variables. The instance's disk will be
66 numbered from 0 to this value minus one.
69 The path to the storage for disk N of the instance. This might be
70 either a block device or a regular file, in which case the OS
71 scripts should use ``losetup`` (if they need to mount it). E.g. the
72 first disk of the instance might be exported as
73 ``DISK_0_PATH=/dev/drbd0``.
76 This is how the hypervisor will export the instance disks: either
77 read-write (``rw``) or read-only (``ro``).
80 (Optional) If applicable to the current hypervisor type: the type
81 of the device exported by the hypervisor. For example, the Xen HVM
82 hypervisor can export disks as either ``paravirtual`` or
86 How files are visible on the node side. This can be either
87 ``block`` (when using block devices) or ``file:type``, where
88 ``type`` is either ``loop`` or ``blktap`` depending on how the
89 hypervisor will be configured. Note that not all backend types
90 apply to all hypervisors.
93 Similar to the ``DISK_COUNT``, this represents the number of NICs
97 The MAC address associated with this interface.
100 The IP address, if any, associated with the N-th NIC of the
104 The NIC mode, either routed or bridged
107 The bridge to which this NIC will be attached. This variable is
108 defined only when the NIC is in bridged mode.
111 If the NIC is in bridged mode, this is the same as
112 ``NIC_%N_BRIDGE``. If it is in routed mode, the routing table
113 which will be used by the hypervisor to insert the appropriate
117 (Optional) If applicable, the type of the exported NIC to the
118 instance, this can be one of: ``rtl8139``, ``ne2k_pci``,
119 ``ne2k_isa``, ``paravirtual``.
122 Each OS parameter (see below) will be exported in its own
123 variable, prefixed with ``OSP_``, and upper-cased. For example, a
124 ``dhcp`` parameter will be exported as ``OSP_DHCP``.
127 If non-zero, this should cause the OS script to generate verbose
128 logs of its execution, for troubleshooting purposes. Currently
129 only ``0`` and ``1`` are valid values.
139 The **create** command is used for creating a new instance from
140 scratch. It has no additional environment variables bside the
143 The ``INSTANCE_NAME`` variable denotes the name of the instance,
144 which is guaranteed to resolve to an IP address. The create script
145 should configure the instance according to this name. It can
146 configure the IP statically or not, depending on the deployment
149 The ``INSTANCE_REINSTALL`` variable is set to ``1`` when this create
150 request is reinstalling an existing instance, rather than creating
151 one anew. This can be used, for example, to preserve some data in the
152 old instance in an OS-specific way.
157 This command is used in order to make a backup of a given disk of
158 the instance. The command should write to stdout a dump of the
159 given block device. The output of this program will be passed
160 during restore to the **import** command.
162 The specific disk to backup is denoted by two additional environment
163 variables: ``EXPORT_INDEX`` which denotes the index in the instance
164 disks structure (and could be used for example to skip the second disk
165 if not needed for backup) and ``EXPORT_DEVICE`` which has the same value
166 as ``DISK_N_PATH`` but is duplicated here for easier usage by shell
167 scripts (rather than parse the ``DISK_...`` variables).
169 To provide the user with an estimate on how long the export will take,
170 a predicted size can be written to the file descriptor passed in the
171 variable ``EXP_SIZE_FD``. The value is in bytes and must be terminated
172 by a newline character (``\n``). Older versions of Ganeti don't
173 support this feature, hence the variable should be checked before
176 if test -n "$EXP_SIZE_FD"; then
177 blockdev --getsize64 $blockdev >&$EXP_SIZE_FD
183 The **import** command is used for restoring an instance from a
184 backup as done by **export**. The arguments are the similar to
185 those passed to **export**, whose output will be provided on
188 The difference in variables is that the current disk is denoted by
189 ``IMPORT_DEVICE`` and ``IMPORT_INDEX`` (instead of ``EXPORT_...``).
194 This command is used in order to perform a rename at the instance
195 OS level, after the instance has been renamed in Ganeti. The
196 command should do whatever steps are required to ensure that the
197 instance is updated to use the new name, if the operating system
200 Note that it is acceptable for the rename script to do nothing at
201 all, however be warned that in this case, there will be a
202 desynchronization between what gnt-instance list shows you and the
203 actual hostname of the instance.
205 The script will be passed one additional environment variable
206 called ``OLD_INSTANCE_NAME`` which holds the old instance name. The
207 ``INSTANCE_NAME`` variable holds the new instance name.
209 A very simple rename script should at least change the hostname and
210 IP address of the instance, leaving the administrator to update the
216 The *verify* script is used to verify consistency of the OS parameters
217 (see below). The command should take one or more arguments denoting
218 what checks should be performed, and return a proper exit code
219 depending on whether the validation failed or succeeded.
221 Currently (API version 20), only one parameter is supported:
222 ``parameters``. This should validate the ``OSP_`` variables from the
223 environment, and output diagnostic messages in case the validation
228 For the ``dhcp`` parameter given as example above, a verification
237 echo "Invalid value '$OSP_DHCP' for the dhcp parameter" 1>&2
252 The ganeti_api_version file is a plain text file containing the
253 version(s) of the guest OS API that this OS definition complies
254 with, one per line. The version documented by this man page is 20,
255 so this file must contain the number 20 followed by a newline if
256 only this version is supported. A script compatible with more than
257 one Ganeti version should contain the most recent version first
258 (i.e. 20), followed by the old version(s) (in this case 15 and/or
264 variants.list is a plain text file containing all the declared supported
265 variants for this OS, one per line. If this file is missing or empty,
266 then the OS won't be considered to support variants.
271 This file declares the parameters supported by the OS, one parameter
272 per line, with name and description (space and/or tab separated). For
275 dhcp Whether to enable (yes) or disable (no) dhcp
276 root_size The size of the root partition, in GiB
278 The parameters can then be used in instance add or modification, as
281 # gnt-instance add -O dhcp=no,root_size=8 ...
287 Backwards compatibility
288 ~~~~~~~~~~~~~~~~~~~~~~~
290 Ganeti 2.3 and up is compatible with API versions 10, 15 and 20. The OS
291 parameters and related scripts (verify) are only supported in
292 version 20. The variants functionality (variants.list, and OS_VARIANT
293 env. var) are supported/present only in version 15 and up.
298 All the scripts should display an usage message when called with a
299 wrong number of arguments or when the first argument is ``-h`` or
302 Upgrading from old versions
303 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
308 The ``parameters.list`` file and ``verify`` script have been
309 added. For no parameters, an empty parameters file and an empty verify
310 script which returns success can be used.
315 The ``variants.list`` file has been added, so OSes should support at
316 least one variant, declaring it in that file and must be prepared to
317 parse the OS_VARIANT environment variable. OSes are free to support more
318 variants than just the declared ones. Note that this file is optional;
319 without it, the variants functionality is disabled.
324 The method for passing data has changed from command line options
325 to environment variables, so scripts should be modified to use
326 these. For an example of how this can be done in a way compatible
327 with both versions, feel free to look at the debootstrap instance's
328 common.sh auxiliary script.
330 Also, instances can have now a variable number of disks, not only
331 two, and a variable number of NICs (instead of fixed one), so the
332 scripts should deal with this. The biggest change is in the
333 import/export, which are called once per disk, instead of once per
339 The rename script has been added. If you don't want to do any
340 changes on the instances after a rename, you can migrate the OS
341 definition to version 5 by creating the rename script simply as::
347 Note that the script must be executable.
349 .. vim: set textwidth=72 :
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