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
34 The OS API version that the rest of the environment conforms to.
37 The instance name the script should operate on.
40 Both names point to the name of the instance's OS as Ganeti knows
41 it. This can simplify the OS scripts by providing the same scripts
42 under multiple names, and then the scripts can use this name to
43 alter their behaviour.
45 With OS API 15 changing the script behavior based on this variable
46 is deprecated: OS_VARIANT should be used instead (see below).
49 The variant of the OS which should be installed. Each OS must
50 support all variants listed under its variants.list file, and may
51 support more. Any more supported variants should be properly
52 documented in the per-OS documentation.
55 The hypervisor of this instance.
58 The number of disks the instance has. The actual disk defitions are
59 in a set of additional variables. The instance's disk will be
60 numbered from 0 to this value minus one.
63 The path to the storage for disk N of the instance. This might be
64 either a block device or a regular file, in which case the OS
65 scripts should use ``losetup`` (if they need to mount it). E.g. the
66 first disk of the instance might be exported as
67 ``DISK_0_PATH=/dev/drbd0``.
70 This is how the hypervisor will export the instance disks: either
71 read-write (``rw``) or read-only (``ro``).
74 (Optional) If applicable to the current hypervisor type: the type
75 of the device exported by the hypervisor. For example, the Xen HVM
76 hypervisor can export disks as either ``paravirtual`` or
80 How files are visible on the node side. This can be either
81 ``block`` (when using block devices) or ``file:type``, where
82 ``type`` is either ``loop`` or ``blktap`` depending on how the
83 hypervisor will be configured. Note that not all backend types
84 apply to all hypervisors.
87 Similar to the ``DISK_COUNT``, this represents the number of NICs
91 The MAC address associated with this interface.
94 The IP address, if any, associated with the N-th NIC of the
98 The NIC mode, either routed or bridged
101 The bridge to which this NIC will be attached. This variable is
102 defined only when the NIC is in bridged mode.
105 If the NIC is in bridged mode, this is the same as
106 ``NIC_%N_BRIDGE``. If it is in routed mode, the routing table
107 which will be used by the hypervisor to insert the appropriate
111 (Optional) If applicable, the type of the exported NIC to the
112 instance, this can be one of: ``rtl8139``, ``ne2k_pci``,
113 ``ne2k_isa``, ``paravirtual``.
116 Each OS parameter (see below) will be exported in its own
117 variable, prefixed with ``OSP_``, and upper-cased. For example, a
118 ``dhcp`` parameter will be exported as ``OSP_DHCP``.
121 If non-zero, this should cause the OS script to generate verbose
122 logs of its execution, for troubleshooting purposes. Currently
123 only ``0`` and ``1`` are valid values.
133 The **create** command is used for creating a new instance from
134 scratch. It has no additional environment variables bside the
137 The ``INSTANCE_NAME`` variable denotes the name of the instance,
138 which is guaranteed to resolve to an IP address. The create script
139 should configure the instance according to this name. It can
140 configure the IP statically or not, depending on the deployment
143 The ``INSTANCE_REINSTALL`` variable is set to ``1`` when this create
144 request is reinstalling an existing instance, rather than creating
145 one anew. This can be used, for example, to preserve some data in the
146 old instance in an OS-specific way.
151 This command is used in order to make a backup of a given disk of
152 the instance. The command should write to stdout a dump of the
153 given block device. The output of this program will be passed
154 during restore to the **import** command.
156 The specific disk to backup is denoted by two additional environment
157 variables: ``EXPORT_INDEX`` which denotes the index in the instance
158 disks structure (and could be used for example to skip the second disk
159 if not needed for backup) and ``EXPORT_DEVICE`` which has the same value
160 as ``DISK_N_PATH`` but is duplicated here for easier usage by shell
161 scripts (rather than parse the ``DISK_...`` variables).
163 To provide the user with an estimate on how long the export will take,
164 a predicted size can be written to the file descriptor passed in the
165 variable ``EXP_SIZE_FD``. The value is in bytes and must be terminated
166 by a newline character (``\n``). Older versions of Ganeti don't
167 support this feature, hence the variable should be checked before
170 if test -n "$EXP_SIZE_FD"; then
171 blockdev --getsize64 $blockdev >&$EXP_SIZE_FD
177 The **import** command is used for restoring an instance from a
178 backup as done by **export**. The arguments are the similar to
179 those passed to **export**, whose output will be provided on
182 The difference in variables is that the current disk is denoted by
183 ``IMPORT_DEVICE`` and ``IMPORT_INDEX`` (instead of ``EXPORT_...``).
188 This command is used in order to perform a rename at the instance
189 OS level, after the instance has been renamed in Ganeti. The
190 command should do whatever steps are required to ensure that the
191 instance is updated to use the new name, if the operating system
194 Note that it is acceptable for the rename script to do nothing at
195 all, however be warned that in this case, there will be a
196 desynchronization between what gnt-instance list shows you and the
197 actual hostname of the instance.
199 The script will be passed one additional environment variable
200 called ``OLD_INSTANCE_NAME`` which holds the old instance name. The
201 ``INSTANCE_NAME`` variable holds the new instance name.
203 A very simple rename script should at least change the hostname and
204 IP address of the instance, leaving the administrator to update the
210 The *verify* script is used to verify consistency of the OS parameters
211 (see below). The command should take one or more arguments denoting
212 what checks should be performed, and return a proper exit code
213 depending on whether the validation failed or succeeded.
215 Currently (API version 20), only one parameter is supported:
216 ``parameters``. This should validate the ``OSP_`` variables from the
217 environment, and output diagnostic messages in case the validation
222 For the ``dhcp`` parameter given as example above, a verification
231 echo "Invalid value '$OSP_DHCP' for the dhcp parameter" 1>&2
246 The ganeti_api_version file is a plain text file containing the
247 version(s) of the guest OS API that this OS definition complies
248 with, one per line. The version documented by this man page is 20,
249 so this file must contain the number 20 followed by a newline if
250 only this version is supported. A script compatible with more than
251 one Ganeti version should contain the most recent version first
252 (i.e. 20), followed by the old version(s) (in this case 15 and/or
258 variants.list is a plain text file containing all the declared
259 supported variants for this OS, one per line. At least one variant
265 This file declares the parameters supported by the OS, one parameter
266 per line, with name and description (space and/or tab separated). For
269 dhcp Whether to enable (yes) or disable (no) dhcp
270 root_size The size of the root partition, in GiB
272 The parameters can then be used in instance add or modification, as
275 # gnt-instance add -O dhcp=no,root_size=8 ...
281 Backwards compatibility
282 ~~~~~~~~~~~~~~~~~~~~~~~
284 Ganeti 2.3 and up is compatible with API versions 10, 15 and 20. The OS
285 parameters and related scripts (verify) are only supported in
286 version 20. The variants functionality (variants.list, and OS_VARIANT
287 env. var) are supported/present only in version 15 and up.
292 All the scripts should display an usage message when called with a
293 wrong number of arguments or when the first argument is ``-h`` or
296 Upgrading from old versions
297 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
302 The ``parameters.list`` file and ``verify`` script have been
303 added. For no parameters, an empty parameters file and an empty verify
304 script which returns success can be used.
309 The ``variants.list`` file has been added, so OSes should support at
310 least one variant, declaring it in that file and must be prepared to
311 parse the OS_VARIANT environment variable. OSes are free to support
312 more variants than just the declared ones.
317 The method for passing data has changed from command line options
318 to environment variables, so scripts should be modified to use
319 these. For an example of how this can be done in a way compatible
320 with both versions, feel free to look at the debootstrap instance's
321 common.sh auxiliary script.
323 Also, instances can have now a variable number of disks, not only
324 two, and a variable number of NICs (instead of fixed one), so the
325 scripts should deal with this. The biggest change is in the
326 import/export, which are called once per disk, instead of once per
332 The rename script has been added. If you don't want to do any
333 changes on the instances after a rename, you can migrate the OS
334 definition to version 5 by creating the rename script simply as::
340 Note that the script must be executable.
342 .. vim: set textwidth=72 :