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.
SEE ALSO¶
nilfs(8),
mount(8),
umount.nilfs2(8),
nilfs_cleanerd(8),
lscp(1).
