mount.nilfs2 - mount a NILFS2 file system
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]
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.
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).
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).
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
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.
mount.nilfs2 is part of the nilfs-utils package and is
available from http://nilfs.sourceforge.net.