gnbd_export(8)

NAME
gnbd_export - the interface to export GNBDs

SYNOPSIS
gnbd_export [OPTION]...

DESCRIPTION
gnbd_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 multipathing, or run GFS on gnbd server machines. To set up dm multipathing 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 internal 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 appropriate 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 ALSO
gnbd_import(8), gnbd(8)