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
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:
-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.
nobarrier
Disable 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 continue.
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.
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 <ryusuke@osrg.net> 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.
SEE ALSO
nilfs(8), mount(8), umount.nilfs2(8), nilfs_cleanerd(8), lscp(1).