gnbd_export(8)gnbd_export(8)NAMEgnbd_export - the interface to export GNBDs
SYNOPSISgnbd_export [OPTION]...
DESCRIPTIONgnbd_export exports local block devices or files as GNBDs.
OPTIONS-a Validate.
This option forces all server processes to send a ping message
to the clients they are connected to. This forces servers with
faulty connections to quit.
-c Enable caching.
Reads from the exported GNBD will take advantage of the linux
page cache. This option is used with -e. NOTE: If this option
is not specified, gnbd will run with a noticeable performance
decrease. Also, if this option is not specified, the exported
GNBD will run in timeout mode, with the default timeout (see the
-t option). With the -c option, it is not necessary to have the
gnbd server machine be part of the cluster. If -c option is not
used, the server machine must already have a cluster manager
running on it. When the first uncached gnbd is exported, the
gnbd_clusterd daemon will be started. This daemon connects to
the cluster manager via the magma interface. WARNING: You must
NOT specify this option if you wish to use gnbd with dm multi‐
pathing, or run GFS on gnbd server machines. To set up dm mul‐
tipathing over gnbd, all gnbds involved must run with caching
disabled. Data corruption will occur if the GNBD devices are
run with caching. Any device that is exported without the -c
option can also be used locally, but you must access the device
directly. You MUST NOT use gnbd_import to import devices
exported from the same machine.
-d pathname
Device.
Specify the device to export as a GNBD. This option is used
with -e. pathname may be either a block device or a regular
file. Usually block devices are used, because this increases
GNBD performance.
-e gnbdname
Export.
Export a device as a GNBD with the Device name gnbdname. You
must also specify the pathname of the device with the -d option.
Once a GNBD has been exported, clients can import it with
gnbd_import.
-h Help.
Print the usage information.
-l List.
List all exported GNBDs and kgnbd_portd server information. The
listing contains each server's number (which is only for inter‐
nal use), its Device name, the pathname of the device that is
being exported, it's size in 512 byte sectors, and information
on whether or not it is cached, and if not, what it's timeout
is.
-O Override
This option allows you to unexport gnbd devices, even if they
are still in use. When an agent other than fence_gnbd is used
to fence gnbd client nodes, occasionally gnbd server threads are
not correctly cleaned up. This causes no performance issues.
However, the affected gnbd devices cannot be unexported. In
this case, using the -O option with either -r or -R will allow
you to unexport the GNBD devices. WARNING: Make sure that no
clients have the GNBD imported before using this option.
-o Readonly
export the server in readonly mode.
-q Quiet.
Only prints out error messages.
-R Remove All.
Remove all exported GNBDs.
-r [GNBD(s)]
Remove.
Remove named GNBD(s).
-u uid Manually set UID.
Manunally set the Universal Identifier for an exported device.
This option is used with -e. The UID is used by device-mapper-
multipath to determine which devices belong in a multipath map.
A device must have a UID to be multipathed. However, for most
SCSI devices the default Get UID command will return an appro‐
priate id (see -U). NOTE: The UID refers to the device being
exported, not the GNBD itself. The UIDs of two GNBD devices
should be equal, only if they are exporting the same underlying
device. This means that both GNBD servers are connected to the
same physical device. WARNING: This should only be used for
exporting shared storage devices, when the -U command does not
work. This should almost never happen for SCSI devices. If two
GNBD devices are not exporting the same underlying device, but
are given the same UID, data corruption WILL occur. You should
not use this option unless -U does not work for your setup, and
you understand why.
-U [command]
Get UID Command.
This is a command the gnbd_export will run to get a Universal
Identifier for the exported device. The UID is necessary to use
device-mapper-multipath with GNBD (see -u for more information).
The command must use the full path of any executeable that you
wish to run. A command can contain the %M, %m or %n escape
sequences. %M will be expanded to the major number of the
exported device, %m will be expaned to the minor number of the
exported device, and %n will be expanded to the sysfs name for
the device. If no command is given, gnbd will use the default
command "/usr/sbin/gnbd_get_uid". This command will work for
most scsi devices.
-t [seconds]
Timeout.
Set the exported GNBD to timeout mode This option is used with
-p. This is the default for uncached GNBDs. For cached GNBDs,
the default is wait mode (For GFS versions up through 5.2, all
GNBDs were in wait mode). In wait mode, if the connection to
the server is lost, the gnbd client waits for the connection to
be reestablished, and then resends all the pending requests. In
timeout mode, if the connection cannot be reestablished or if
the gnbd client does not receive a response from the server
within the timeout period, the gnbd client returns all pending
and future requests as failures until the imported GNBD is
closed. The default timeout period is 60 seconds. Timeout mode
is necessary for failover to work with dm multipathing over
gnbd.
-v Verbose.
Increase the verbosity of the output. This option is the most
useful with -l. If it is used along with -l, an extended list
of information on each exported device will be printed.
-V Version information.
Print out version information.
SEE ALSOgnbd_import(8), gnbd(8)gnbd_export(8)
