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. Howerver, 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. With this option, invocation of nilfs_cleanerd(8) is
skipped. To add entries to mtab and invoke the garbage collector later, the -f
option is available.

-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. (Eigher 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://www.nilfs.org.