gfs2_mount

Section: Maintenance Commands (8)
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NAME

gfs2_mount - GFS2 mount options

 

SYNOPSIS

mount [StandardMountOptions] -t gfs2 DEVICE MOUNTPOINT -o [GFS2Option1,GFS2Option2,GFS2OptionX...]

 

DESCRIPTION

GFS2 may be used as a local (single computer) filesystem, but its real purpose is in clusters, where multiple computers (nodes) share a common storage device.

Above is the format typically used to mount a GFS2 filesystem, using the mount(8) command. The device may be any block device on which you have created a GFS2 filesystem. Examples include a single disk partition (e.g. /dev/sdb3), a loopback device, a device exported from another node (e.g. an iSCSI device or a gnbd(8) device), or a logical volume (typically comprised of a number of individual disks).

device does not necessarily need to match the device name as seen on another node in the cluster, nor does it need to be a logical volume. However, the use of a cluster-aware volume manager such as CLVM2 (see lvm(8)) will guarantee that the managed devices are named identically on each node in a cluster (for much easier management), and will allow you to configure a very large volume from multiple storage units (e.g. disk drives).

device must make the entire filesystem storage area visible to the computer. That is, you cannot mount different parts of a single filesystem on different computers. Each computer must see an entire filesystem. You may, however, mount several GFS2 filesystems if you want to distribute your data storage in a controllable way.

mountpoint is the same as dir in the mount(8) man page.

This man page describes GFS2-specific options that can be passed to the GFS2 file system at mount time, using the -o flag. There are many other -o options handled by the generic mount command mount(8). However, the options described below are specifically for GFS2, and are not interpreted by the mount command nor by the kernel's Virtual File System. GFS2 and non-GFS2 options may be intermingled after the -o, separated by commas (but no spaces).

As an alternative to mount command line options, you may send mount options to gfs2 using "gfs2_tool margs" (after loading the gfs2 kernel module, but before mounting GFS2). For example, you may need to do this when working from an initial ramdisk initrd(4). The options are restricted to the ones described on this man page (no general mount(8) options will be recognized), must not be preceded by -o, and must be separated by commas (no spaces). Example:

# gfs2_tool margs "lockproto=lock_nolock,ignore_local_fs"

Options loaded via "gfs2_tool margs" have a lifetime of only one GFS2 mount. If you wish to mount another GFS2 filesystem, you must set another group of options with "gfs2_tool margs".

The options debug, acl, quota, suiddir, and data can be changed after mount using the "mount -o remount,option /mountpoint" command. The options debug, acl, and suiddir support the "no" prefix. For example, "noacl" turns off what "acl" turns on.

If you have trouble mounting GFS2, check the syslog (e.g. /var/log/messages) for specific error messages.

 

OPTIONS

lockproto=LockModuleName
This specifies which inter-node lock protocol is used by the GFS2 filesystem for this mount, overriding the default lock protocol name stored in the filesystem's on-disk superblock.

The LockModuleName must be an exact match of the protocol name presented by the lock module when it registers with the lock harness. Traditionally, this matches the .o filename of the lock module, e.g. lock_dlm, or lock_nolock.

The default lock protocol name is written to disk initially when creating the filesystem with gfs2_mkfs(8), -p option. It can be changed on-disk by using the gfs2_tool(8) utility's sb proto command.

The lockproto mount option should be used only under special circumstances in which you want to temporarily use a different lock protocol without changing the on-disk default.

locktable=LockTableName
This specifies the identity of the cluster and of the filesystem for this mount, overriding the default cluster/filesystem identify stored in the filesystem's on-disk superblock. The cluster/filesystem name is recognized globally throughout the cluster, and establishes a unique namespace for the inter-node locking system, enabling the mounting of multiple GFS2 filesystems.

The format of LockTableName is lock-module-specific. For lock_dlm, the format is clustername:fsname. For lock_nolock, the field is ignored.

The default cluster/filesystem name is written to disk initially when creating the filesystem with gfs2_mkfs(8), -t option. It can be changed on-disk by using the gfs2_tool(8) utility's sb table command.

The locktable mount option should be used only under special circumstances in which you want to mount the filesystem in a different cluster, or mount it as a different filesystem name, without changing the on-disk default.

localcaching
This flag tells GFS2 that it is running as a local (not clustered) filesystem, so it can turn on some block caching optimizations that can't be used when running in cluster mode.

This is turned on automatically by the lock_nolock module, but can be overridden by using the ignore_local_fs option.

localflocks
This flag tells GFS2 that it is running as a local (not clustered) filesystem, so it can allow the kernel VFS layer to do all flock and fcntl file locking. When running in cluster mode, these file locks require inter-node locks, and require the support of GFS2. When running locally, better performance is achieved by letting VFS handle the whole job.

This is turned on automatically by the lock_nolock module, but can be overridden by using the ignore_local_fs option.

debug
Causes GFS2 to oops when encountering an error that would cause the mount to withdraw or print an assertion warning. This option should probably not be used in a production system.
ignore_local_fs
By default, using the nolock lock module automatically turns on the localcaching and localflocks optimizations. ignore_local_fs forces GFS2 to treat the filesystem as if it were a multihost (clustered) filesystem, with localcaching and localflocks optimizations turned off.
upgrade
This flag tells GFS2 to upgrade the filesystem's on-disk format to the version supported by the current GFS2 software installation on this computer. If you try to mount an old-version disk image, GFS2 will notify you via a syslog message that you need to upgrade. Try mounting again, using the -o upgrade option. When upgrading, only one node may mount the GFS2 filesystem.
num_glockd=Number
Tunes GFS2 to alleviate memory pressure when rapidly aquiring many locks (e.g. several processes scanning through huge directory trees). GFS2' glockd kernel daemon cleans up memory for no-longer-needed glocks. Multiple instances of the daemon clean up faster than a single instance. The default value is one daemon, with a maximum of 16. Since this option was introduced, other methods of rapid cleanup have been developed within GFS2, so this option may go away in the future.
acl
Enables POSIX Access Control List acl(5) support within GFS2.
spectator
Mount this filesystem using a special form of read-only mount. The mount does not use one of the filesystem's journals.
suiddir
Sets owner of any newly created file or directory to be that of parent directory, if parent directory has S_ISUID permission attribute bit set. Sets S_ISUID in any new directory, if its parent directory's S_ISUID is set. Strips all execution bits on a new file, if parent directory owner is different from owner of process creating the file. Set this option only if you know why you are setting it.
quota=[off/account/on]
Turns quotas on or off for a filesystem. Setting the quotas to be in the "account" state causes the per UID/GID usage statistics to be correctly maintained by the filesystem, limit and warn values are ignored. The default value is "off".
data=[ordered/writeback]
When data=ordered is set, the user data modified by a transaction is flushed to the disk before the transaction is commited to disk. This should prevent the user from seeing uninitialized blocks in a file after a crash. Data=writeback mode writes the user data to the disk at any time after it's dirtied. This doesn't provide the same consistency guarantee as ordered mode, but it should be slightly faster for some workloads. The default is ordered mode.

 

LINKS

http://sources.redhat.com/cluster
-- home site of GFS2
http://www.suse.de/~agruen/acl/linux-acls/
-- good writeup on ACL support in Linux

 

SEE ALSO

gfs2(8), mount(8) for general mount options, chmod(1) and chmod(2) for access permission flags, acl(5) for access control lists, lvm(8) for volume management, ccs(7) for cluster management, umount(8), initrd(4).


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
LINKS
SEE ALSO

linux.jgfs.net manual pages