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gnt-instance(8) Ganeti | Version @GANETI_VERSION@

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Name

----

gnt-instance - Ganeti instance administration

Synopsis

--------

**gnt-instance** {command} [arguments...]

DESCRIPTION

-----------

The **gnt-instance** command is used for instance administration in

the Ganeti system.

COMMANDS

--------

Creation/removal/querying

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

ADD

^^^

| **add**

| {-t|\--disk-template {diskless | file \| plain \| drbd \| rbd}}

| {\--disk=*N*: {size=*VAL* \| adopt=*LV*}[,vg=*VG*][,metavg=*VG*][,mode=*ro\|rw*]

|  \| {-s|\--os-size} *SIZE*}

| [\--no-ip-check] [\--no-name-check] [\--no-start] [\--no-install]

| [\--net=*N* [:options...] \| \--no-nics]

| [{-B|\--backend-parameters} *BEPARAMS*]

| [{-H|\--hypervisor-parameters} *HYPERVISOR* [: option=*value*... ]]

| [{-O|\--os-parameters} *param*=*value*... ]

| [\--file-storage-dir *dir\_path*] [\--file-driver {loop \| blktap}]

| {{-n|\--node} *node[:secondary-node]* \| {-I|\--iallocator} *name*}

| {{-o|\--os-type} *os-type*}

| [\--submit]

| [\--ignore-ipolicy]

| {*instance*}

Creates a new instance on the specified host. The *instance* argument

must be in DNS, but depending on the bridge/routing setup, need not be

in the same network as the nodes in the cluster.

The ``disk`` option specifies the parameters for the disks of the

instance. The numbering of disks starts at zero, and at least one disk

needs to be passed. For each disk, either the size or the adoption

source needs to be given, and optionally the access mode (read-only or

the default of read-write) and the LVM volume group can also be

specified (via the ``vg`` key). For DRBD devices, a different VG can

be specified for the metadata device using the ``metavg`` key.  The

size is interpreted (when no unit is given) in mebibytes. You can also

use one of the suffixes *m*, *g* or *t* to specify the exact the units

used; these suffixes map to mebibytes, gibibytes and tebibytes.

When using the ``adopt`` key in the disk definition, Ganeti will

reuse those volumes (instead of creating new ones) as the

instance's disks. Ganeti will rename these volumes to the standard

format, and (without installing the OS) will use them as-is for the

instance. This allows migrating instances from non-managed mode

(e.g. plain KVM with LVM) to being managed via Ganeti. Please note that

this works only for the \`plain' disk template (see below for

template details).

Alternatively, a single-disk instance can be created via the ``-s``

option which takes a single argument, the size of the disk. This is

similar to the Ganeti 1.2 version (but will only create one disk).

The minimum disk specification is therefore ``--disk 0:size=20G`` (or

``-s 20G`` when using the ``-s`` option), and a three-disk instance

can be specified as ``--disk 0:size=20G --disk 1:size=4G --disk

2:size=100G``.

The ``--no-ip-check`` skips the checks that are done to see if the

instance's IP is not already alive (i.e. reachable from the master

node).

The ``--no-name-check`` skips the check for the instance name via

the resolver (e.g. in DNS or /etc/hosts, depending on your setup).

Since the name check is used to compute the IP address, if you pass

this option you must also pass the ``--no-ip-check`` option.

If you don't want the instance to automatically start after

creation, this is possible via the ``--no-start`` option. This will

leave the instance down until a subsequent **gnt-instance start**

command.

The NICs of the instances can be specified via the ``--net``

option. By default, one NIC is created for the instance, with a

random MAC, and set up according the the cluster level nic

parameters. Each NIC can take these parameters (all optional):

mac

    either a value or 'generate' to generate a new unique MAC

ip

    specifies the IP address assigned to the instance from the Ganeti

    side (this is not necessarily what the instance will use, but what

    the node expects the instance to use)

mode

    specifies the connection mode for this nic: routed, bridged or

    openvswitch.

link

    in bridged or openvswitch mode specifies the interface to attach

    this NIC to, in routed mode it's intended to differentiate between

    different routing tables/instance groups (but the meaning is

    dependent on the network script, see **gnt-cluster**\(8) for more

    details). Note that openvswitch support is also hypervisor

    dependent.

Of these "mode" and "link" are nic parameters, and inherit their

default at cluster level.  Alternatively, if no network is desired for

the instance, you can prevent the default of one NIC with the

``--no-nics`` option.

The ``-o (--os-type)`` option specifies the operating system to be

installed.  The available operating systems can be listed with

**gnt-os list**.  Passing ``--no-install`` will however skip the OS

installation, allowing a manual import if so desired. Note that the

no-installation mode will automatically disable the start-up of the

instance (without an OS, it most likely won't be able to start-up

successfully).

The ``-B (--backend-parameters)`` option specifies the backend

parameters for the instance. If no such parameters are specified, the

values are inherited from the cluster. Possible parameters are:

maxmem

    the maximum memory size of the instance; as usual, suffixes can be

    used to denote the unit, otherwise the value is taken in mebibytes

minmem

    the minimum memory size of the instance; as usual, suffixes can be

    used to denote the unit, otherwise the value is taken in mebibytes

vcpus

    the number of VCPUs to assign to the instance (if this value makes

    sense for the hypervisor)

auto\_balance

    whether the instance is considered in the N+1 cluster checks

    (enough redundancy in the cluster to survive a node failure)

always\_failover

    ``True`` or ``False``, whether the instance must be failed over

    (shut down and rebooted) always or it may be migrated (briefly

    suspended)

Note that before 2.6 Ganeti had a ``memory`` parameter, which was the

only value of memory an instance could have. With the

``maxmem``/``minmem`` change Ganeti guarantees that at least the minimum

memory is always available for an instance, but allows more memory to be

used (up to the maximum memory) should it be free.

The ``-H (--hypervisor-parameters)`` option specified the hypervisor

to use for the instance (must be one of the enabled hypervisors on the

cluster) and optionally custom parameters for this instance. If not

other options are used (i.e. the invocation is just -H *NAME*) the

instance will inherit the cluster options. The defaults below show the

cluster defaults at cluster creation time.

The possible hypervisor options are as follows:

boot\_order

    Valid for the Xen HVM and KVM hypervisors.

    A string value denoting the boot order. This has different meaning

    for the Xen HVM hypervisor and for the KVM one.

    For Xen HVM, The boot order is a string of letters listing the boot

    devices, with valid device letters being:

    a

        floppy drive

    c

        hard disk

    d

        CDROM drive

    n

        network boot (PXE)

    The default is not to set an HVM boot order, which is interpreted

    as 'dc'.

    For KVM the boot order is either "floppy", "cdrom", "disk" or

    "network".  Please note that older versions of KVM couldn't netboot

    from virtio interfaces. This has been fixed in more recent versions

    and is confirmed to work at least with qemu-kvm 0.11.1. Also note

    that if you have set the ``kernel_path`` option, that will be used

    for booting, and this setting will be silently ignored.

blockdev\_prefix

    Valid for the Xen HVM and PVM hypervisors.

    Relevant to non-pvops guest kernels, in which the disk device names

    are given by the host.  Allows one to specify 'xvd', which helps run

    Red Hat based installers, driven by anaconda.

floppy\_image\_path

    Valid for the KVM hypervisor.

    The path to a floppy disk image to attach to the instance.  This

    is useful to install Windows operating systems on Virt/IO disks

    because you can specify here the floppy for the drivers at

    installation time.

cdrom\_image\_path

    Valid for the Xen HVM and KVM hypervisors.

    The path to a CDROM image to attach to the instance.

cdrom2\_image\_path

    Valid for the KVM hypervisor.

    The path to a second CDROM image to attach to the instance.

    **NOTE**: This image can't be used to boot the system. To do that

    you have to use the 'cdrom\_image\_path' option.

nic\_type

    Valid for the Xen HVM and KVM hypervisors.

    This parameter determines the way the network cards are presented

    to the instance. The possible options are:

    - rtl8139 (default for Xen HVM) (HVM & KVM)

    - ne2k\_isa (HVM & KVM)

    - ne2k\_pci (HVM & KVM)

    - i82551 (KVM)

    - i82557b (KVM)

    - i82559er (KVM)

    - pcnet (KVM)

    - e1000 (KVM)

    - paravirtual (default for KVM) (HVM & KVM)

disk\_type

    Valid for the Xen HVM and KVM hypervisors.

    This parameter determines the way the disks are presented to the

    instance. The possible options are:

    - ioemu [default] (HVM & KVM)

    - ide (HVM & KVM)

    - scsi (KVM)

    - sd (KVM)

    - mtd (KVM)

    - pflash (KVM)

cdrom\_disk\_type

    Valid for the KVM hypervisor.

    This parameter determines the way the cdroms disks are presented

    to the instance. The default behavior is to get the same value of

    the earlier parameter (disk_type). The possible options are:

    - paravirtual

    - ide

    - scsi

    - sd

    - mtd

    - pflash

vnc\_bind\_address

    Valid for the Xen HVM and KVM hypervisors.

    Specifies the address that the VNC listener for this instance

    should bind to. Valid values are IPv4 addresses. Use the address

    0.0.0.0 to bind to all available interfaces (this is the default)

    or specify the address of one of the interfaces on the node to

    restrict listening to that interface.

vnc\_tls

    Valid for the KVM hypervisor.

    A boolean option that controls whether the VNC connection is

    secured with TLS.

vnc\_x509\_path

    Valid for the KVM hypervisor.

    If ``vnc_tls`` is enabled, this options specifies the path to the

    x509 certificate to use.

vnc\_x509\_verify

    Valid for the KVM hypervisor.

spice\_bind

    Valid for the KVM hypervisor.

    Specifies the address or interface on which the SPICE server will

    listen. Valid values are:

    - IPv4 addresses, including 0.0.0.0 and 127.0.0.1

    - IPv6 addresses, including :: and ::1

    - names of network interfaces

    If a network interface is specified, the SPICE server will be bound

    to one of the addresses of that interface.

spice\_ip\_version

    Valid for the KVM hypervisor.

    Specifies which version of the IP protocol should be used by the

    SPICE server.

    It is mainly intended to be used for specifying what kind of IP

    addresses should be used if a network interface with both IPv4 and

    IPv6 addresses is specified via the ``spice_bind`` parameter. In

    this case, if the ``spice_ip_version`` parameter is not used, the

    default IP version of the cluster will be used.

spice\_password\_file

    Valid for the KVM hypervisor.

    Specifies a file containing the password that must be used when

    connecting via the SPICE protocol. If the option is not specified,

    passwordless connections are allowed.

spice\_image\_compression

    Valid for the KVM hypervisor.

    Configures the SPICE lossless image compression. Valid values are:

    - auto_glz

    - auto_lz

    - quic

    - glz

    - lz

    - off

spice\_jpeg\_wan\_compression

    Valid for the KVM hypervisor.

    Configures how SPICE should use the jpeg algorithm for lossy image

    compression on slow links. Valid values are:

    - auto

    - never

    - always

spice\_zlib\_glz\_wan\_compression

    Valid for the KVM hypervisor.

    Configures how SPICE should use the zlib-glz algorithm for lossy image

    compression on slow links. Valid values are:

    - auto

    - never

    - always

spice\_streaming\_video

    Valid for the KVM hypervisor.

    Configures how SPICE should detect video streams. Valid values are:

    - off

    - all

    - filter

spice\_playback\_compression

    Valid for the KVM hypervisor.

    Configures whether SPICE should compress audio streams or not.

spice\_use\_tls

    Valid for the KVM hypervisor.

    Specifies that the SPICE server must use TLS to encrypt all the

    traffic with the client.

spice\_tls\_ciphers

    Valid for the KVM hypervisor.

    Specifies a list of comma-separated ciphers that SPICE should use

    for TLS connections. For the format, see man **cipher**\(1).

spice\_use\_vdagent

    Valid for the KVM hypervisor.

    Enables or disables passing mouse events via SPICE vdagent.

cpu\_type

    Valid for the KVM hypervisor.

    This parameter determines the emulated cpu for the instance. If this

    parameter is empty (which is the default configuration), it will not

    be passed to KVM.

    Be aware of setting this parameter to ``"host"`` if you have nodes

    with different CPUs from each other. Live migration may stop working

    in this situation.

    For more information please refer to the KVM manual.

acpi

    Valid for the Xen HVM and KVM hypervisors.

    A boolean option that specifies if the hypervisor should enable

    ACPI support for this instance. By default, ACPI is disabled.

pae

    Valid for the Xen HVM and KVM hypervisors.

    A boolean option that specifies if the hypervisor should enabled

    PAE support for this instance. The default is false, disabling PAE

    support.

use\_localtime

    Valid for the Xen HVM and KVM hypervisors.

    A boolean option that specifies if the instance should be started

    with its clock set to the localtime of the machine (when true) or

    to the UTC (When false). The default is false, which is useful for

    Linux/Unix machines; for Windows OSes, it is recommended to enable

    this parameter.

kernel\_path

    Valid for the Xen PVM and KVM hypervisors.

    This option specifies the path (on the node) to the kernel to boot

    the instance with. Xen PVM instances always require this, while for

    KVM if this option is empty, it will cause the machine to load the

    kernel from its disks (and the boot will be done accordingly to

    ``boot_order``).

kernel\_args

    Valid for the Xen PVM and KVM hypervisors.

    This options specifies extra arguments to the kernel that will be

    loaded. device. This is always used for Xen PVM, while for KVM it

    is only used if the ``kernel_path`` option is also specified.

    The default setting for this value is simply ``"ro"``, which

    mounts the root disk (initially) in read-only one. For example,

    setting this to single will cause the instance to start in

    single-user mode.

initrd\_path

    Valid for the Xen PVM and KVM hypervisors.

    This option specifies the path (on the node) to the initrd to boot

    the instance with. Xen PVM instances can use this always, while

    for KVM if this option is only used if the ``kernel_path`` option

    is also specified. You can pass here either an absolute filename

    (the path to the initrd) if you want to use an initrd, or use the

    format no\_initrd\_path for no initrd.

root\_path

    Valid for the Xen PVM and KVM hypervisors.

    This options specifies the name of the root device. This is always

    needed for Xen PVM, while for KVM it is only used if the

    ``kernel_path`` option is also specified.

    Please note, that if this setting is an empty string and the

    hypervisor is Xen it will not be written to the Xen configuration

    file

serial\_console

    Valid for the KVM hypervisor.

    This boolean option specifies whether to emulate a serial console

    for the instance.

serial\_speed

    Valid for the KVM hypervisor.

    This integer option specifies the speed of the serial console.

    Common values are 9600, 19200, 38400, 57600 and 115200: choose the

    one which works on your system. (The default is 38400 for historical

    reasons, but newer versions of kvm/qemu work with 115200)

disk\_cache

    Valid for the KVM hypervisor.

    The disk cache mode. It can be either default to not pass any

    cache option to KVM, or one of the KVM cache modes: none (for

    direct I/O), writethrough (to use the host cache but report

    completion to the guest only when the host has committed the

    changes to disk) or writeback (to use the host cache and report

    completion as soon as the data is in the host cache). Note that

    there are special considerations for the cache mode depending on

    version of KVM used and disk type (always raw file under Ganeti),

    please refer to the KVM documentation for more details.

security\_model

    Valid for the KVM hypervisor.

    The security model for kvm. Currently one of *none*, *user* or

    *pool*. Under *none*, the default, nothing is done and instances

    are run as the Ganeti daemon user (normally root).

    Under *user* kvm will drop privileges and become the user

    specified by the security\_domain parameter.

    Under *pool* a global cluster pool of users will be used, making

    sure no two instances share the same user on the same node. (this

    mode is not implemented yet)

security\_domain

    Valid for the KVM hypervisor.

    Under security model *user* the username to run the instance

    under.  It must be a valid username existing on the host.

    Cannot be set under security model *none* or *pool*.

kvm\_flag

    Valid for the KVM hypervisor.

    If *enabled* the -enable-kvm flag is passed to kvm. If *disabled*

    -disable-kvm is passed. If unset no flag is passed, and the

    default running mode for your kvm binary will be used.

mem\_path

    Valid for the KVM hypervisor.

    This option passes the -mem-path argument to kvm with the path (on

    the node) to the mount point of the hugetlbfs file system, along

    with the -mem-prealloc argument too.

use\_chroot

    Valid for the KVM hypervisor.

    This boolean option determines whether to run the KVM instance in a

    chroot directory.

    If it is set to ``true``, an empty directory is created before

    starting the instance and its path is passed via the -chroot flag

    to kvm. The directory is removed when the instance is stopped.

    It is set to ``false`` by default.

migration\_downtime

    Valid for the KVM hypervisor.

    The maximum amount of time (in ms) a KVM instance is allowed to be

    frozen during a live migration, in order to copy dirty memory

    pages. Default value is 30ms, but you may need to increase this

    value for busy instances.

    This option is only effective with kvm versions >= 87 and qemu-kvm

    versions >= 0.11.0.

cpu\_mask

    Valid for the Xen, KVM and LXC hypervisors.

    The processes belonging to the given instance are only scheduled

    on the specified CPUs.

    The format of the mask can be given in three forms. First, the word

    "all", which signifies the common case where all VCPUs can live on

    any CPU, based on the hypervisor's decisions.

    Second, a comma-separated list of CPU IDs or CPU ID ranges. The

    ranges are defined by a lower and higher boundary, separated by a

    dash, and the boundaries are inclusive. In this form, all VCPUs of

    the instance will be mapped on the selected list of CPUs. Example:

    ``0-2,5``, mapping all VCPUs (no matter how many) onto physical CPUs

    0, 1, 2 and 5.

    The last form is used for explicit control of VCPU-CPU pinnings. In

    this form, the list of VCPU mappings is given as a colon (:)

    separated list, whose elements are the possible values for the

    second or first form above. In this form, the number of elements in

    the colon-separated list _must_ equal the number of VCPUs of the

    instance.

    Example:

    .. code-block:: bash

      # Map the entire instance to CPUs 0-2

      gnt-instance modify -H cpu_mask=0-2 my-inst

      # Map vCPU 0 to physical CPU 1 and vCPU 1 to CPU 3 (assuming 2 vCPUs)

      gnt-instance modify -H cpu_mask=1:3 my-inst

      # Pin vCPU 0 to CPUs 1 or 2, and vCPU 1 to any CPU

      gnt-instance modify -H cpu_mask=1-2:all my-inst

      # Pin vCPU 0 to any CPU, vCPU 1 to CPUs 1, 3, 4 or 5, and CPU 2 to

      # CPU 0 (backslashes for escaping the comma)

      gnt-instance modify -H cpu_mask=all:1\\,3-5:0 my-inst

      # Pin entire VM to CPU 0

      gnt-instance modify -H cpu_mask=0 my-inst

      # Turn off CPU pinning (default setting)

      gnt-instance modify -H cpu_mask=all my-inst

cpu\_cap

    Valid for the Xen hypervisor.

    Set the maximum amount of cpu usage by the VM. The value is a percentage

    between 0 and (100 * number of VCPUs). Default cap is 0: unlimited.

cpu\_weight

    Valid for the Xen hypervisor.

    Set the cpu time ratio to be allocated to the VM. Valid values are

    between 1 and 65535. Default weight is 256.

usb\_mouse

    Valid for the KVM hypervisor.

    This option specifies the usb mouse type to be used. It can be

    "mouse" or "tablet". When using VNC it's recommended to set it to

    "tablet".

keymap

    Valid for the KVM hypervisor.

    This option specifies the keyboard mapping to be used. It is only

    needed when using the VNC console. For example: "fr" or "en-gb".

reboot\_behavior

    Valid for Xen PVM, Xen HVM and KVM hypervisors.

    Normally if an instance reboots, the hypervisor will restart it. If

    this option is set to ``exit``, the hypervisor will treat a reboot

    as a shutdown instead.

    It is set to ``reboot`` by default.

cpu\_cores

    Valid for the KVM hypervisor.

    Number of emulated CPU cores.

cpu\_threads

    Valid for the KVM hypervisor.

    Number of emulated CPU threads.

cpu\_sockets

    Valid for the KVM hypervisor.

    Number of emulated CPU sockets.

soundhw

    Valid for the KVM hypervisor.

    Comma separated list of emulated sounds cards, or "all" to enable

    all the available ones.

usb\_devices

    Valid for the KVM hypervisor.

    Comma separated list of usb devices. These can be emulated devices

    or passthrough ones, and each one gets passed to kvm with its own

    ``-usbdevice`` option. See the **qemu**\(1) manpage for the syntax

    of the possible components.

vga

    Valid for the KVM hypervisor.

    Emulated vga mode, passed the the kvm -vga option.

kvm\_extra

    Valid for the KVM hypervisor.

    Any other option to the KVM hypervisor, useful tweaking anything

    that Ganeti doesn't support.

machine\_version

    Valid for the KVM hypervisor.

    Use in case an instance must be booted with an exact type of

    machine version (due to e.g. outdated drivers). In case it's not set

    the default version supported by your version of kvm is used.

The ``-O (--os-parameters)`` option allows customisation of the OS

parameters. The actual parameter names and values depends on the OS

being used, but the syntax is the same key=value. For example, setting

a hypothetical ``dhcp`` parameter to yes can be achieved by::

    gnt-instance add -O dhcp=yes ...

The ``-I (--iallocator)`` option specifies the instance allocator plugin

to use (``.`` means the default allocator). If you pass in this option

the allocator will select nodes for this instance automatically, so you

don't need to pass them with the ``-n`` option. For more information

please refer to the instance allocator documentation.

The ``-t (--disk-template)`` options specifies the disk layout type

for the instance.  The available choices are:

diskless

    This creates an instance with no disks. Its useful for testing only

    (or other special cases).

file

    Disk devices will be regular files.

plain

    Disk devices will be logical volumes.

drbd

    Disk devices will be drbd (version 8.x) on top of lvm volumes.

rbd

    Disk devices will be rbd volumes residing inside a RADOS cluster.

The optional second value of the ``-n (--node)`` is used for the drbd

template type and specifies the remote node.

If you do not want gnt-instance to wait for the disk mirror to be

synced, use the ``--no-wait-for-sync`` option.

The ``--file-storage-dir`` specifies the relative path under the

cluster-wide file storage directory to store file-based disks. It is

useful for having different subdirectories for different

instances. The full path of the directory where the disk files are

stored will consist of cluster-wide file storage directory + optional

subdirectory + instance name. Example:

``@RPL_FILE_STORAGE_DIR@/mysubdir/instance1.example.com``. This

option is only relevant for instances using the file storage backend.

The ``--file-driver`` specifies the driver to use for file-based

disks. Note that currently these drivers work with the xen hypervisor

only. This option is only relevant for instances using the file

storage backend. The available choices are:

loop

    Kernel loopback driver. This driver uses loopback devices to

    access the filesystem within the file. However, running I/O

    intensive applications in your instance using the loop driver

    might result in slowdowns. Furthermore, if you use the loopback

    driver consider increasing the maximum amount of loopback devices

    (on most systems it's 8) using the max\_loop param.

blktap

    The blktap driver (for Xen hypervisors). In order to be able to

    use the blktap driver you should check if the 'blktapctrl' user

    space disk agent is running (usually automatically started via

    xend).  This user-level disk I/O interface has the advantage of

    better performance. Especially if you use a network file system

    (e.g. NFS) to store your instances this is the recommended choice.

If ``--ignore-ipolicy`` is given any instance policy violations occuring

during this operation are ignored.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

Example::

    # gnt-instance add -t file --disk 0:size=30g -B maxmem=512 -o debian-etch \

      -n node1.example.com --file-storage-dir=mysubdir instance1.example.com

    # gnt-instance add -t plain --disk 0:size=30g -B maxmem=1024,minmem=512 \

      -o debian-etch -n node1.example.com instance1.example.com

    # gnt-instance add -t plain --disk 0:size=30g --disk 1:size=100g,vg=san \

      -B maxmem=512 -o debian-etch -n node1.example.com instance1.example.com

    # gnt-instance add -t drbd --disk 0:size=30g -B maxmem=512 -o debian-etch \

      -n node1.example.com:node2.example.com instance2.example.com

BATCH-CREATE

^^^^^^^^^^^^

**batch-create** {instances\_file.json}

This command (similar to the Ganeti 1.2 **batcher** tool) submits

multiple instance creation jobs based on a definition file. The

instance configurations do not encompass all the possible options for

the **add** command, but only a subset.

The instance file should be a valid-formed JSON file, containing a

dictionary with instance name and instance parameters. The accepted

parameters are:

disk\_size

    The size of the disks of the instance.

disk\_template

    The disk template to use for the instance, the same as in the

    **add** command.

backend

    A dictionary of backend parameters.

hypervisor

    A dictionary with a single key (the hypervisor name), and as value

    the hypervisor options. If not passed, the default hypervisor and

    hypervisor options will be inherited.

mac, ip, mode, link

    Specifications for the one NIC that will be created for the

    instance. 'bridge' is also accepted as a backwards compatible

    key.

nics

    List of nics that will be created for the instance. Each entry

    should be a dict, with mac, ip, mode and link as possible keys.

    Please don't provide the "mac, ip, mode, link" parent keys if you

    use this method for specifying nics.

primary\_node, secondary\_node

    The primary and optionally the secondary node to use for the

    instance (in case an iallocator script is not used).

iallocator

    Instead of specifying the nodes, an iallocator script can be used

    to automatically compute them.

start

    whether to start the instance

ip\_check

    Skip the check for already-in-use instance; see the description in

    the **add** command for details.

name\_check

    Skip the name check for instances; see the description in the

    **add** command for details.

file\_storage\_dir, file\_driver

    Configuration for the file disk type, see the **add** command for

    details.

A simple definition for one instance can be (with most of the

parameters taken from the cluster defaults)::

    {

      "instance3": {

        "template": "drbd",

        "os": "debootstrap",

        "disk_size": ["25G"],

        "iallocator": "dumb"

      },

      "instance5": {

        "template": "drbd",

        "os": "debootstrap",

        "disk_size": ["25G"],

        "iallocator": "dumb",

        "hypervisor": "xen-hvm",

        "hvparams": {"acpi": true},

        "backend": {"maxmem": 512, "minmem": 256}

      }

    }

The command will display the job id for each submitted instance, as

follows::

    # gnt-instance batch-create instances.json

    instance3: 11224

    instance5: 11225

REMOVE

^^^^^^

**remove** [\--ignore-failures] [\--shutdown-timeout=*N*] [\--submit]

[\--force] {*instance*}

Remove an instance. This will remove all data from the instance and

there is *no way back*. If you are not sure if you use an instance

again, use **shutdown** first and leave it in the shutdown state for a

while.

The ``--ignore-failures`` option will cause the removal to proceed

even in the presence of errors during the removal of the instance

(e.g. during the shutdown or the disk removal). If this option is not

given, the command will stop at the first error.

The ``--shutdown-timeout`` is used to specify how much time to wait

before forcing the shutdown (e.g. ``xm destroy`` in Xen, killing the

kvm process for KVM, etc.). By default two minutes are given to each

instance to stop.

The ``--force`` option is used to skip the interactive confirmation.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

Example::

    # gnt-instance remove instance1.example.com

LIST

^^^^

| **list**

| [\--no-headers] [\--separator=*SEPARATOR*] [\--units=*UNITS*] [-v]

| [{-o|\--output} *[+]FIELD,...*] [\--filter] [instance...]

Shows the currently configured instances with memory usage, disk

usage, the node they are running on, and their run status.

The ``--no-headers`` option will skip the initial header line. The

``--separator`` option takes an argument which denotes what will be

used between the output fields. Both these options are to help

scripting.

The units used to display the numeric values in the output varies,

depending on the options given. By default, the values will be

formatted in the most appropriate unit. If the ``--separator`` option

is given, then the values are shown in mebibytes to allow parsing by

scripts. In both cases, the ``--units`` option can be used to enforce

a given output unit.

The ``-v`` option activates verbose mode, which changes the display of

special field states (see **ganeti**\(7)).

The ``-o (--output)`` option takes a comma-separated list of output

fields. The available fields and their meaning are:

@QUERY_FIELDS_INSTANCE@

If the value of the option starts with the character ``+``, the new

field(s) will be added to the default list. This allows one to quickly

see the default list plus a few other fields, instead of retyping the

entire list of fields.

There is a subtle grouping about the available output fields: all

fields except for ``oper_state``, ``oper_ram``, ``oper_vcpus`` and

``status`` are configuration value and not run-time values. So if you

don't select any of the these fields, the query will be satisfied

instantly from the cluster configuration, without having to ask the

remote nodes for the data. This can be helpful for big clusters when

you only want some data and it makes sense to specify a reduced set of

output fields.

If exactly one argument is given and it appears to be a query filter

(see **ganeti**\(7)), the query result is filtered accordingly. For

ambiguous cases (e.g. a single field name as a filter) the ``--filter``

(``-F``) option forces the argument to be treated as a filter (e.g.

``gnt-instance list -F admin_state``).

The default output field list is: ``name``, ``os``, ``pnode``,

``admin_state``, ``oper_state``, ``oper_ram``.

LIST-FIELDS

^^^^^^^^^^^

**list-fields** [field...]

Lists available fields for instances.

INFO

^^^^

**info** [-s \| \--static] [\--roman] {\--all \| *instance*}

Show detailed information about the given instance(s). This is

different from **list** as it shows detailed data about the instance's

disks (especially useful for the drbd disk template).

If the option ``-s`` is used, only information available in the

configuration file is returned, without querying nodes, making the

operation faster.

Use the ``--all`` to get info about all instances, rather than

explicitly passing the ones you're interested in.

The ``--roman`` option can be used to cause envy among people who like

ancient cultures, but are stuck with non-latin-friendly cluster

virtualization technologies.

MODIFY

^^^^^^

| **modify**

| [{-H|\--hypervisor-parameters} *HYPERVISOR\_PARAMETERS*]

| [{-B|\--backend-parameters} *BACKEND\_PARAMETERS*]

| [{-m|\--runtime-memory} *SIZE*]

| [\--net add*[:options]* \| \--net [*N*:]remove \| \--net *N:options*]

| [\--disk add:size=*SIZE*[,vg=*VG*][,metavg=*VG*] \| \--disk [*N*:]remove \|

|  \--disk *N*:mode=*MODE*]

| [{-t|\--disk-template} plain | {-t|\--disk-template} drbd -n *new_secondary*] [\--no-wait-for-sync]

| [\--os-type=*OS* [\--force-variant]]

| [{-O|\--os-parameters} *param*=*value*... ]

| [\--offline \| \--online]

| [\--submit]

| [\--ignore-ipolicy]

| {*instance*}

Modifies the memory size, number of vcpus, ip address, MAC address

and/or nic parameters for an instance. It can also add and remove

disks and NICs to/from the instance. Note that you need to give at

least one of the arguments, otherwise the command complains.

The ``-H (--hypervisor-parameters)``, ``-B (--backend-parameters)``

and ``-O (--os-parameters)`` options specifies hypervisor, backend and

OS parameter options in the form of name=value[,...]. For details

which options can be specified, see the **add** command.

The ``-t (--disk-template)`` option will change the disk template of

the instance.  Currently only conversions between the plain and drbd

disk templates are supported, and the instance must be stopped before

attempting the conversion. When changing from the plain to the drbd

disk template, a new secondary node must be specified via the ``-n``

option. The option ``--no-wait-for-sync`` can be used when converting

to the ``drbd`` template in order to make the instance available for

startup before DRBD has finished resyncing.

The ``-m (--runtime-memory)`` option will change an instance's runtime

memory to the given size (in MB if a different suffix is not specified),

by ballooning it up or down to the new value.

The ``--disk add:size=``*SIZE* option adds a disk to the instance. The

optional ``vg=``*VG* option specifies an LVM volume group other than

the default volume group to create the disk on. For DRBD disks, the

``metavg=``*VG* option specifies the volume group for the metadata

device. ``--disk`` *N*``:add,size=``**SIZE** can be used to add a

disk at a specific index. The ``--disk remove`` option will remove the

last disk of the instance. Use ``--disk `` *N*``:remove`` to remove a

disk by its index. The ``--disk`` *N*``:mode=``*MODE* option will change

the mode of the Nth disk of the instance between read-only (``ro``) and

read-write (``rw``).

The ``--net add:``*options* and ``--net`` *N*``:add,``*options* option

will add a new network interface to the instance. The available options

are the same as in the **add** command (``mac``, ``ip``, ``link``,

``mode``). The ``--net remove`` will remove the last network interface

of the instance (``--net`` *N*``:remove`` for a specific index), while

the ``--net`` *N*``:``*options* option will change the parameters of the Nth

instance network interface.

The option ``-o (--os-type)`` will change the OS name for the instance

(without reinstallation). In case an OS variant is specified that is

not found, then by default the modification is refused, unless

``--force-variant`` is passed. An invalid OS will also be refused,

unless the ``--force`` option is given.

The ``--online`` and ``--offline`` options are used to transition an

instance into and out of the ``offline`` state. An instance can be

turned offline only if it was previously down. The ``--online`` option

fails if the instance was not in the ``offline`` state, otherwise it

changes instance's state to ``down``. These modifications take effect

immediately.

If ``--ignore-ipolicy`` is given any instance policy violations occuring

during this operation are ignored.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

Most of the changes take effect at the next restart. If the instance is

running, there is no effect on the instance.

REINSTALL

^^^^^^^^^

| **reinstall** [{-o|\--os-type} *os-type*] [\--select-os] [-f *force*]

| [\--force-multiple]

| [\--instance \| \--node \| \--primary \| \--secondary \| \--all]

| [{-O|\--os-parameters} *OS\_PARAMETERS*] [\--submit] {*instance*...}

Reinstalls the operating system on the given instance(s). The

instance(s) must be stopped when running this command. If the ``-o

(--os-type)`` is specified, the operating system is changed.

The ``--select-os`` option switches to an interactive OS reinstall.

The user is prompted to select the OS template from the list of

available OS templates. OS parameters can be overridden using ``-O

(--os-parameters)`` (more documentation for this option under the

**add** command).

Since this is a potentially dangerous command, the user will be

required to confirm this action, unless the ``-f`` flag is passed.

When multiple instances are selected (either by passing multiple

arguments or by using the ``--node``, ``--primary``, ``--secondary``

or ``--all`` options), the user must pass the ``--force-multiple``

options to skip the interactive confirmation.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

RENAME

^^^^^^

| **rename** [\--no-ip-check] [\--no-name-check] [\--submit]

| {*instance*} {*new\_name*}

Renames the given instance. The instance must be stopped when running

this command. The requirements for the new name are the same as for

adding an instance: the new name must be resolvable and the IP it

resolves to must not be reachable (in order to prevent duplicate IPs

the next time the instance is started). The IP test can be skipped if

the ``--no-ip-check`` option is passed.

Note that you can rename an instance to its same name, to force

re-executing the os-specific rename script for that instance, if

needed.

The ``--no-name-check`` skips the check for the new instance name via

the resolver (e.g. in DNS or /etc/hosts, depending on your setup) and

that the resolved name matches the provided name. Since the name check

is used to compute the IP address, if you pass this option you must also

pass the ``--no-ip-check`` option.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

Starting/stopping/connecting to console

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

STARTUP

^^^^^^^

| **startup**

| [\--force] [\--ignore-offline]

| [\--force-multiple] [\--no-remember]

| [\--instance \| \--node \| \--primary \| \--secondary \| \--all \|

| \--tags \| \--node-tags \| \--pri-node-tags \| \--sec-node-tags]

| [{-H|\--hypervisor-parameters} ``key=value...``]

| [{-B|\--backend-parameters} ``key=value...``]

| [\--submit] [\--paused]

| {*name*...}

Starts one or more instances, depending on the following options.  The

four available modes are:

\--instance

    will start the instances given as arguments (at least one argument

    required); this is the default selection

\--node

    will start the instances who have the given node as either primary

    or secondary

\--primary

    will start all instances whose primary node is in the list of nodes

    passed as arguments (at least one node required)

\--secondary

    will start all instances whose secondary node is in the list of

    nodes passed as arguments (at least one node required)

\--all

    will start all instances in the cluster (no arguments accepted)

\--tags

    will start all instances in the cluster with the tags given as

    arguments

\--node-tags

    will start all instances in the cluster on nodes with the tags

    given as arguments

\--pri-node-tags

    will start all instances in the cluster on primary nodes with the

    tags given as arguments

\--sec-node-tags

    will start all instances in the cluster on secondary nodes with the

    tags given as arguments

Note that although you can pass more than one selection option, the

last one wins, so in order to guarantee the desired result, don't pass

more than one such option.

Use ``--force`` to start even if secondary disks are failing.

``--ignore-offline`` can be used to ignore offline primary nodes and

mark the instance as started even if the primary is not available.

The ``--force-multiple`` will skip the interactive confirmation in the

case the more than one instance will be affected.

The ``--no-remember`` option will perform the startup but not change

the state of the instance in the configuration file (if it was stopped

before, Ganeti will still think it needs to be stopped). This can be

used for testing, or for a one shot-start where you don't want the

watcher to restart the instance if it crashes.

The ``-H (--hypervisor-parameters)`` and ``-B (--backend-parameters)``

options specify temporary hypervisor and backend parameters that can

be used to start an instance with modified parameters. They can be

useful for quick testing without having to modify an instance back and

forth, e.g.::

    # gnt-instance start -H kernel_args="single" instance1

    # gnt-instance start -B maxmem=2048 instance2

The first form will start the instance instance1 in single-user mode,

and the instance instance2 with 2GB of RAM (this time only, unless

that is the actual instance memory size already). Note that the values

override the instance parameters (and not extend them): an instance

with "kernel\_args=ro" when started with -H kernel\_args=single will

result in "single", not "ro single".

The ``--paused`` option is only valid for Xen and kvm hypervisors.  This

pauses the instance at the start of bootup, awaiting ``gnt-instance

console`` to unpause it, allowing the entire boot process to be

monitored for debugging.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

Example::

    # gnt-instance start instance1.example.com

    # gnt-instance start --node node1.example.com node2.example.com

    # gnt-instance start --all

SHUTDOWN

^^^^^^^^

| **shutdown**

| [\--timeout=*N*]

| [\--force] [\--force-multiple] [\--ignore-offline] [\--no-remember]

| [\--instance \| \--node \| \--primary \| \--secondary \| \--all \|

| \--tags \| \--node-tags \| \--pri-node-tags \| \--sec-node-tags]

| [\--submit]

| {*name*...}

Stops one or more instances. If the instance cannot be cleanly stopped

during a hardcoded interval (currently 2 minutes), it will forcibly

stop the instance (equivalent to switching off the power on a physical

machine).

The ``--timeout`` is used to specify how much time to wait before

forcing the shutdown (e.g. ``xm destroy`` in Xen, killing the kvm

process for KVM, etc.). By default two minutes are given to each

instance to stop.

The ``--instance``, ``--node``, ``--primary``, ``--secondary``,

``--all``, ``--tags``, ``--node-tags``, ``--pri-node-tags`` and

``--sec-node-tags`` options are similar as for the **startup** command

and they influence the actual instances being shutdown.

``--ignore-offline`` can be used to ignore offline primary nodes and

force the instance to be marked as stopped. This option should be used

with care as it can lead to an inconsistent cluster state.

Use ``--force`` to be able to shutdown an instance even when it's marked

as offline. This is useful is an offline instance ends up in the

``ERROR_up`` state, for example.

The ``--no-remember`` option will perform the shutdown but not change

the state of the instance in the configuration file (if it was running

before, Ganeti will still thinks it needs to be running). This can be

useful for a cluster-wide shutdown, where some instances are marked as

up and some as down, and you don't want to change the running state:

you just need to disable the watcher, shutdown all instances with

``--no-remember``, and when the watcher is activated again it will

restore the correct runtime state for all instances.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

Example::

    # gnt-instance shutdown instance1.example.com

    # gnt-instance shutdown --all

REBOOT

^^^^^^

| **reboot**

| [{-t|\--type} *REBOOT-TYPE*]

| [\--ignore-secondaries]

| [\--shutdown-timeout=*N*]

| [\--force-multiple]

| [\--instance \| \--node \| \--primary \| \--secondary \| \--all \|

| \--tags \| \--node-tags \| \--pri-node-tags \| \--sec-node-tags]

| [\--submit]

| [*name*...]

Reboots one or more instances. The type of reboot depends on the value

of ``-t (--type)``. A soft reboot does a hypervisor reboot, a hard reboot

does a instance stop, recreates the hypervisor config for the instance

and starts the instance. A full reboot does the equivalent of

**gnt-instance shutdown && gnt-instance startup**.  The default is

hard reboot.

For the hard reboot the option ``--ignore-secondaries`` ignores errors

for the secondary node while re-assembling the instance disks.

The ``--instance``, ``--node``, ``--primary``, ``--secondary``,

``--all``, ``--tags``, ``--node-tags``, ``--pri-node-tags`` and

``--sec-node-tags`` options are similar as for the **startup** command

and they influence the actual instances being rebooted.

The ``--shutdown-timeout`` is used to specify how much time to wait

before forcing the shutdown (xm destroy in xen, killing the kvm

process, for kvm). By default two minutes are given to each instance

to stop.

The ``--force-multiple`` will skip the interactive confirmation in the

case the more than one instance will be affected.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

Example::

    # gnt-instance reboot instance1.example.com

    # gnt-instance reboot --type=full instance1.example.com

CONSOLE

^^^^^^^

**console** [\--show-cmd] {*instance*}

Connects to the console of the given instance. If the instance is not

up, an error is returned. Use the ``--show-cmd`` option to display the

command instead of executing it.

For HVM instances, this will attempt to connect to the serial console

of the instance. To connect to the virtualized "physical" console of a

HVM instance, use a VNC client with the connection info from the

**info** command.

For Xen/kvm instances, if the instance is paused, this attempts to

unpause the instance after waiting a few seconds for the connection to

the console to be made.

Example::

    # gnt-instance console instance1.example.com

Disk management

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

REPLACE-DISKS

^^^^^^^^^^^^^

**replace-disks** [\--submit] [\--early-release] [\--ignore-ipolicy] {-p}

[\--disks *idx*] {*instance*}

**replace-disks** [\--submit] [\--early-release] [\--ignore-ipolicy] {-s}

[\--disks *idx*] {*instance*}

**replace-disks** [\--submit] [\--early-release] [\--ignore-ipolicy]

{{-I\|\--iallocator} *name* \| {{-n|\--new-secondary} *node* } {*instance*}

**replace-disks** [\--submit] [\--early-release] [\--ignore-ipolicy]

{-a\|\--auto} {*instance*}

This command is a generalized form for replacing disks. It is

currently only valid for the mirrored (DRBD) disk template.

The first form (when passing the ``-p`` option) will replace the disks

on the primary, while the second form (when passing the ``-s`` option

will replace the disks on the secondary node. For these two cases (as

the node doesn't change), it is possible to only run the replace for a

subset of the disks, using the option ``--disks`` which takes a list

of comma-delimited disk indices (zero-based), e.g. 0,2 to replace only

the first and third disks.

The third form (when passing either the ``--iallocator`` or the

``--new-secondary`` option) is designed to change secondary node of the

instance. Specifying ``--iallocator`` makes the new secondary be

selected automatically by the specified allocator plugin (use ``.`` to

indicate the default allocator), otherwise the new secondary node will

be the one chosen manually via the ``--new-secondary`` option.

Note that it is not possible to select an offline or drained node as a

new secondary.

The fourth form (when using ``--auto``) will automatically determine

which disks of an instance are faulty and replace them within the same

node. The ``--auto`` option works only when an instance has only

faulty disks on either the primary or secondary node; it doesn't work

when both sides have faulty disks.

The ``--early-release`` changes the code so that the old storage on

secondary node(s) is removed early (before the resync is completed)

and the internal Ganeti locks for the current (and new, if any)

secondary node are also released, thus allowing more parallelism in

the cluster operation. This should be used only when recovering from a

disk failure on the current secondary (thus the old storage is already

broken) or when the storage on the primary node is known to be fine

(thus we won't need the old storage for potential recovery).

The ``--ignore-ipolicy`` let the command ignore instance policy

violations if replace-disks changes groups and the instance would

violate the new groups instance policy.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

ACTIVATE-DISKS

^^^^^^^^^^^^^^

**activate-disks** [\--submit] [\--ignore-size] [\--wait-for-sync] {*instance*}

Activates the block devices of the given instance. If successful, the

command will show the location and name of the block devices::

    node1.example.com:disk/0:/dev/drbd0

    node1.example.com:disk/1:/dev/drbd1

In this example, *node1.example.com* is the name of the node on which

the devices have been activated. The *disk/0* and *disk/1* are the

Ganeti-names of the instance disks; how they are visible inside the

instance is hypervisor-specific. */dev/drbd0* and */dev/drbd1* are the

actual block devices as visible on the node.

The ``--ignore-size`` option can be used to activate disks ignoring

the currently configured size in Ganeti. This can be used in cases

where the configuration has gotten out of sync with the real-world

(e.g. after a partially-failed grow-disk operation or due to rounding

in LVM devices). This should not be used in normal cases, but only

when activate-disks fails without it.

The ``--wait-for-sync`` option will ensure that the command returns only

after the instance's disks are synchronised (mostly for DRBD); this can

be useful to ensure consistency, as otherwise there are no commands that

can wait until synchronisation is done. However when passing this

option, the command will have additional output, making it harder to

parse the disk information.

Note that it is safe to run this command while the instance is already

running.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

DEACTIVATE-DISKS

^^^^^^^^^^^^^^^^

**deactivate-disks** [-f] [\--submit] {*instance*}

De-activates the block devices of the given instance. Note that if you

run this command for an instance with a drbd disk template, while it

is running, it will not be able to shutdown the block devices on the

primary node, but it will shutdown the block devices on the secondary

nodes, thus breaking the replication.

The ``-f``/``--force`` option will skip checks that the instance is

down; in case the hypervisor is confused and we can't talk to it,

normally Ganeti will refuse to deactivate the disks, but with this

option passed it will skip this check and directly try to deactivate

the disks. This can still fail due to the instance actually running or

other issues.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

GROW-DISK

^^^^^^^^^

| **grow-disk** [\--no-wait-for-sync] [\--submit] [\--absolute]

| {*instance*} {*disk*} {*amount*}

Grows an instance's disk. This is only possible for instances having a

plain, drbd, file, sharedfile or rbd disk template.

Note that this command only change the block device size; it will not

grow the actual filesystems, partitions, etc. that live on that

disk. Usually, you will need to:

#. use **gnt-instance grow-disk**

#. reboot the instance (later, at a convenient time)

#. use a filesystem resizer, such as **ext2online**\(8) or

   **xfs\_growfs**\(8) to resize the filesystem, or use **fdisk**\(8) to

   change the partition table on the disk

The *disk* argument is the index of the instance disk to grow. The

*amount* argument is given as a number which can have a suffix (like the

disk size in instance create); if the suffix is missing, the value will

be interpreted as mebibytes.

By default, the *amount* value represents the desired increase in the

disk size (e.g. an amount of 1G will take a disk of size 3G to 4G). If

the optional ``--absolute`` parameter is passed, then the *amount*

argument doesn't represent the delta, but instead the desired final disk

size (e.g. an amount of 8G will take a disk of size 4G to 8G).

For instances with a drbd template, note that the disk grow operation

might complete on one node but fail on the other; this will leave the

instance with different-sized LVs on the two nodes, but this will not

create problems (except for unused space).

If you do not want gnt-instance to wait for the new disk region to be

synced, use the ``--no-wait-for-sync`` option.

See **ganeti**\(7) for a description of ``--submit`` and other common

options.

Example (increase the first disk for instance1 by 16GiB)::

    # gnt-instance grow-disk instance1.example.com 0 16g

Example for increasing the disk size to a certain size::

   # gnt-instance grow-disk --absolute instance1.example.com 0 32g

Also note that disk shrinking is not supported; use **gnt-backup

export** and then **gnt-backup import** to reduce the disk size of an

instance.

RECREATE-DISKS

^^^^^^^^^^^^^^

| **recreate-disks** [\--submit]

| [{-n node1:[node2] \| {-I\|\--iallocator *name*}}]

| [\--disk=*N*[:[size=*VAL*][,mode=*ro\|rw*]]] {*instance*}

Recreates all or a subset of disks of the given instance.

Note that this functionality should only be used for missing disks; if

any of the given disks already exists, the operation will fail.  While

this is suboptimal, recreate-disks should hopefully not be needed in

normal operation and as such the impact of this is low.

If only a subset should be recreated, any number of ``disk`` options can

be specified. It expects a disk index and an optional list of disk

parameters to change. Only ``size`` and ``mode`` can be changed while

recreating disks. To recreate all disks while changing parameters on

a subset only, a ``--disk`` option must be given for every disk of the

instance.

Optionally the instance's disks can be recreated on different

nodes. This can be useful if, for example, the original nodes of the

instance have gone down (and are marked offline), so we can't recreate

on the same nodes. To do this, pass the new node(s) via ``-n`` option,

with a syntax similar to the **add** command. The number of nodes

passed must equal the number of nodes that the instance currently

has. Note that changing nodes is only allowed when all disks are

replaced, e.g. when no ``--disk`` option is passed.

Another method of choosing which nodes to place the instance on is by

using the specified iallocator, passing the ``--iallocator`` option.

The primary and secondary nodes will be chosen by the specified