Provided by: gfs2-utils_3.1.3-0ubuntu1_i386 bug


       gfs2 - GFS2 reference guide


       Overview of the GFS2 filesystem


       GFS2  is  a  clustered  filesystem,  designed  for sharing data between
       multiple nodes connected to a common shared storage device. It can also
       be  used  as  a  local  filesystem  on a single node, however since the
       design is  aimed  at  clusters,  that  will  usually  result  in  lower
       performance  than  using  a filesystem designed specifically for single
       node use.

       GFS2 is a journaling filesystem and one journal is  required  for  each
       node  that  will  mount  the  filesystem.  The one exception to that is
       spectator mounts which are equivalent to  mounting  a  read-only  block
       device  and  as  such  can  neither  recover  a journal or write to the
       filesystem, so do not require a journal assigned to them.


              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  LockProtoName  must  be  one  of  the   supported   locking
              protocols, currently these are lock_nolock and lock_dlm.

              The default lock protocol name is written to disk initially when
              creating the filesystem with mkfs.gfs2(8), -p option.  It can be
              changed  on-disk  by  using  the gfs2_tool(8) utility's sb proto

              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.  Using  the
              incorrect  lock  protocol  on  a cluster filesystem mounted from
              more than one node will almost certainly  result  in  filesystem

              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

              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 mkfs.gfs2(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.

              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.

              Setting errors=panic causes GFS2 to oops  when  encountering  an
              error  that would otherwise cause the mount to withdraw or print
              an assertion warning. The default  setting  is  errors=withdraw.
              This  option  should  not  be  used  in a production system.  It
              replaces the earlier debug option on kernel versions 2.6.31  and

       acl    Enables POSIX Access Control List acl(5) support within GFS2.

              Mount  this  filesystem using a special form of read-only mount.
              The mount does not use one of  the  filesystem's  journals.  The
              node is unable to recover journals for other nodes.

              A synonym for spectator

              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.

              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".

              Causes GFS2 to generate "discard" I/O requests for blocks  which
              have  been  freed.  These  can  be  used by suitable hardware to
              implement thin-provisioning and similar schemes. This feature is
              supported in kernel version 2.6.30 and above.

              This  option,  which  defaults  to  on,  causes GFS2 to send I/O
              barriers when flushing the journal. The option is  automatically
              turned  off  if  the  underlying  device  does  not  support I/O
              barriers. We highly recommend the use of I/O barriers with  GFS2
              at  all  times  unless  the  block device is designed so that it
              cannot lose its write cache content (e.g. its on a  UPS,  or  it
              doesn't have a write cache)

              This  is  similar to the ext3 commit= option in that it sets the
              maximum number of seconds between journal commits  if  there  is
              dirty  data  in  the  journal.  The  default is 60 seconds. This
              option is only provided in kernel versions 2.6.31 and above.

              When  data=ordered  is  set,  the  user  data  modified   by   a
              transaction  is  flushed  to  the disk before the transaction is
              committed 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.

       meta   This option results in selecting the meta filesystem root rather
              than the normal filesystem root. This option  is  normally  only
              used  by  the  GFS2  utility functions. Altering any file on the
              GFS2 meta filesystem may render the filesystem unusable, so only
              experts in the GFS2 on-disk layout should use this option.

              This  sets the number of seconds for which a change in the quota
              information may sit on one node  before  being  written  to  the
              quota file. This is the preferred way to set this parameter. The
              value is an integer number of seconds  greater  than  zero.  The
              default is 60 seconds. Shorter settings result in faster updates
              of the lazy quota information and  less  likelihood  of  someone
              exceeding   their   quota.   Longer   settings  make  filesystem
              operations involving quotas faster and more efficient.

              Setting statfs_quantum to 0 is the preferred way to set the slow
              version  of  statfs. The default value is 30 secs which sets the
              maximum time period before statfs changes will be syned  to  the
              master  statfs  file.  This can be adjusted to allow for faster,
              less accurate statfs values or slower more accurate values. When
              set to 0, statfs will always report the true values.

              This  setting  provides a bound on the maximum percentage change
              in the statfs information on a local basis before it  is  synced
              back  to the master statfs file, even if the time period has not
              expired. If the  setting  of  statfs_quantum  is  0,  then  this
              setting is ignored.


       GFS2  doesn't  support  errors=remount-ro  or  data=journal.  It is not
       possible to switch support  for  user  and  group  quotas  on  and  off
       independently  of  each  other.  Some  of the error messages are rather
       cryptic, if you encounter one of  these  messages  check  firstly  that
       gfs_controld  is  running and secondly that you have enough journals on
       the filesystem for the number of nodes in use.


       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).

       The GFS2 documentation has been split into a number of sections:

       gfs2_edit(8) A GFS2 debug tool (use with caution) fsck.gfs2(8) The GFS2
       file   system   checker   gfs2_grow(8)   Growing  a  GFS2  file  system
       gfs2_jadd(8) Adding a journal to a GFS2 file system mkfs.gfs2(8) Make a
       GFS2 file system gfs2_quota(8) Manipulate GFS2 disk quotas gfs2_tool(8)
       Tool to manipulate a GFS2 file system (obsolete)  tunegfs2(8)  Tool  to
       manipulate GFS2 superblocks