Ubuntu Manpage: mount.nilfs2 - mount a NILFS2 file system

NAME

       mount.nilfs2 - mount a NILFS2 file system

SYNOPSIS

       mount -t nilfs2 [-finrvw] [-o options [,...]] device dir
       mount -t nilfs2 [-finrvw] [-o options [,...]] device | dir

       mount.nilfs2 [-fnrvw] [-o options [,...]] device dir

       mount.nilfs2 [-V]

DESCRIPTION

       mount.nilfs2  serves  to attach a NILFS2 file system on the specified directory dir. It is intended to be
       executed from mount(8), and will invoke the garbage collector nilfs_cleanerd(8)  after  an  actual  mount
       system  call  has  succeeded.   Conversely,  umount.nilfs2(8)  will shutdown the garbage collector before
       detaching the file system.

       The standard command line interface is the first form:
              mount -t nilfs2 [options] device dir
       This tells the kernel to attach the NILFS2 file system on device at the directory dir.  With  the  second
       form, the mount program tries to find out a missing device or dir argument from the /etc/fstab table.

       The  third  form,  which  directly  invokes  mount.nilfs2, is also usable since mount.nilfs2 maintains by
       itself the system mount state such as the list of mounted file systems described in  /etc/mtab.  However,
       the  first  or the second form is usually recommended because some expansive options are not supported by
       the third form.

OPTIONS

       The full set of options used by an invocation of mount(8) is determined by extracting  the  options  from
       the  fstab table, then applying any options specified by the -o argument, and finally applying a -r or -w
       option, when present.

       See mount(8) for the full set of options.  Commonly used options are as follows:

       -V     Output version.

       -f     Fakes mounting the file system, meaning that the actual system call will be skipped.  This  option
              is  used  to  add entries for devices that were mounted earlier with the -n option. It can also be
              used for invoking nilfs_cleanerd(8) skipped previously.

       -i     Don't call mount.nilfs2.  This disables garbage collection and handling of pseudo mount options.

       -n     Mount without writing in /etc/mtab.  This is necessary for example when /etc  is  on  a  read-only
              file system.

       -r     Mount the file system read-only.  A synonym is "-o ro".

       -v     Verbose mode.

       -w     Mount the file system read/write. This is the default. A synonym is "-o rw".

       -o     Options  are  specified  with  a -o flag followed by a comma separated string of options.  Some of
              these options are only useful when they appear in the /etc/fstab file.   For  standard  filesystem
              options, see mount(8).

NILFS2 SPECIFIC MOUNT OPTIONS

The following options apply only to the NILFS2 filesystem. They all follow the -o flag.

barrier / nobarrier
These options enable/disable (default is enabled) barrier writes for the block I/O to a lower
device. The barrier write serves an important role to ensure consistency of filesystems after a
system crash or power failure. NILFS2 uses this feature by default to assure the reliability.
For devices not supporting the barrier write, it will be disabled automatically and a warning will
be logged.

cp=checkpoint-number
Specify the checkpoint-number of the snapshot to be mounted. Checkpoints and snapshots are listed
by lscp(1). Only the checkpoints marked as snapshot are mountable with this option. Note that
the read-only mount option must be specified together.

errors=continue / errors=remount-ro / errors=panic
Define the behaviour when an error is encountered. (Either ignore errors and just mark the file
system erroneous and continue, or remount the file system read-only, or panic and halt the
system.) The default is remount-ro. In earlier kernels than Linux 2.6.35, continue was the
default.

pp=protection-period
Specify the protection-period for the cleaner daemon (in seconds). nilfs_cleanerd never deletes
recent checkpoints whose elapsed time from its creation is smaller than protection-period.

nogc Disable garbage collection. The cleaner daemon will not be started. It can be be started
manually, but in that case it must also be stopped manually before unmounting.

order=relaxed / order=strict
Specify order semantics for file data. Metadata is always written to follow the POSIX semantics
about the order of filesystem operations.

relaxed
Apply relaxed order semantics that allows modified data blocks to be written to disk
without making a checkpoint if no metadata update is going. This mode is equivalent to the
ordered data mode of the ext3 filesystem except for the updates on data blocks still
conserve atomicity. This will improve synchronous write performance for overwriting. This
is the default mode.

strict Apply strict in-order semantics that preserves sequence of all file operations including
overwriting of data blocks. That means, it is guaranteed that no overtaking of events
occurs in the recovered file system after a crash. Unlike journaling filesystems, NILFS2
does not write a same block twice to disk. So there is no significant performance
degradation in comparison with the relaxed mode except for file overwriting.

norecovery
Disable recovery of the filesystem on mount. This disables every write access on the device for
read-only mounts or snapshots. This option will fail for r/w mounts on an unclean volume.

discard / nodiscard
These options enable/disable (default is disabled) the use of discard/TRIM commands. The
discard/TRIM commands are sent to the underlying block device when blocks are freed. This is
useful for SSD devices and sparse/thinly-provisioned LUNs. (since 2.6.34).

RETURN CODES

       The return codes of mount.nilfs2 conform to those of mount(8); the following codes could be returned (the
       bits can be ORed):

       0      success

       1      incorrect invocation or permissions

       2      system error (out of memory, cannot fork, no more loop devices)

       4      internal bug

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded

AUTHOR

       mount.nilfs2 is written by Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> for NILFS2, based on the mount
       program included in the util-linux package.

AVAILABILITY

       mount.nilfs2 is part of the nilfs-utils package and is available from http://nilfs.sourceforge.net.