NAME
mount_memfs: mount, umount — mount and unmount MemFS file systems
SYNOPSIS
/usr/sbin/mount
[-l]
[-p|-v]
/usr/sbin/mount
-a
[-F
memfs]
[-eQ]
/usr/sbin/mount
[-F
memfs]
[-eQV]
[-o
specific_options]
directory
/usr/sbin/umount
-a
[-F
memfs]
[-v]
/usr/sbin/umount
[-v]
[-V]
directory
DESCRIPTION
The
mount
command mounts file systems.
Only
a superuser
can mount file systems.
Other users can use
mount
to list mounted file systems.
The
mount
command attaches
a removable file system, to
directory,
a directory on the file tree.
directory,
which must already exist,
will become the name of the root of the newly mounted file system.
directory
must be given as an absolute path name.
mount
can be invoked on any removable file system, except the
/
directory.
It is important to note that
mount_memfs
does an internal
mkfs
and hence a separate
mkfs
is not needed for MemFS filesystems.
It constructs the MemFS
filesystem in the buffer cache.
The MemFS blocks will be swapped out of buffer cache when there is
buffer cache or system memory pressure.
MemFS blocks that are swapped out of the buffer cache are stored in
memory allocated to a user process associated with every MemFS mount
instance.
The user process is created during a
mount
and destroyed with a corresponding
umount.
The tunable
memfs_bufcache_swappct
can be used to mark the threshold for swapping out MemFS blocks from the
buffer cache to the user process (see
memfs_bufcache_swappct(5)).
If
mount
is invoked without any arguments,
it lists all of the mounted file systems from the file system mount table,
/etc/mnttab.
The
umount
command unmounts mounted file systems.
Only a superuser can unmount file systems.
Options (mount)
mount
recognizes the following options:
- -a
Attempt to mount all file systems described in
/etc/fstab.
All optional fields in
/etc/fstab
must be included and supported.
If
-F
memfs
is specified, all MemFS file systems in
/etc/fstab
are mounted. If
noauto
is specified in an entry's option list, this entry is skipped.
File systems are not necessarily mounted in the order listed in
/etc/fstab.
- -e
Verbose mode.
Write a message to standard output
indicating which file system is being mounted.
- -F memfs
Specify the MemFS file system type (see
fstyp(1M)).
- -l
Limit actions to local file systems only.
- -o specific_options
Specify options specific to the MemFS file system type.
specific_options
is a list of comma separated suboptions and/or keyword/attribute pairs
intended for the MemFS specific module of the command.
The following
specific_options
are valid on MemFS file systems.
- defaults
Use all default options.
- size
The size for the MemFS filesystem.
Append to
size,
kb
or
KB
to indicate the value is in kilobytes,
mb
or
MB
to indicate megabytes, or
gb
or
GB
to indicate gigabytes.
The default value is the percentage of maximum buffer cache
size that can be occupied by MemFS, as specified by the
memfs_bufcache_swappct
tunable.
The size of MemFS file systems is limited by
UFS_MAXDEVBLK,
defined in
<sys/fs.h>,
which is 256 GB - 1, or 268,435,455 blocks.
- suid
Allow set-user-ID execution (default).
- nosuid
Do not allow set-user-ID execution.
- -p
Report the list of mounted file systems in the
/etc/fstab
format.
- -Q
Prevent the display of error messages
resulting from an attempt to mount already mounted file systems.
- -v
Report the regular output with file system type and flags;
however,
directory
and
special
fields are reversed.
The
special
field for
memfs
always contains the text
memfs.
- -V
Echo the completed command line, but performs no other action.
The command line is generated
by incorporating the user-specified options
and other information derived from
/etc/fstab.
This option allows the user to verify the command line.
Options (umount)
umount
recognizes the following options:
- -a
Attempt to unmount all file systems described in
/etc/mnttab.
All optional fields in
/etc/mnttab
must be included and supported.
If
-F
memfs
is specified, all MemFS file systems in
/etc/mnttab
are unmounted.
File systems are not necessarily unmounted in the order listed in
/etc/mnttab.
- -F memfs
Specify the MemFS file system type (see
fstyp(1M)).
- -v
Verbose mode.
Write a message to standard output
indicating which file system is being unmounted.
- -V
Echo the completed command line, but performs no other action.
The command line is generated
by incorporating the user-specified options
and other information derived from
/etc/fstab.
This option allows the user to verify the command line.
Notes
Quotas are not available for MemFS filesystems.
MemFS filesystems are largefiles-enabled.
MemFS filesystems do not support forced unmount.
MemFS filesystems cannot be mounted read only.
DIAGNOSTICS
umount
complains if the directory is not mounted or if it is busy.
The file system is busy if it contains an open file
or some logged-in user's working directory.
EXAMPLES
Mount a MemFS of size 100 MB on
/mnt:
mount -F memfs -o size=100MB /mnt
Unmount a local MemFS disk:
AUTHOR
mount
was developed by HP,
AT&T,
the University of California, Berkeley,
and Sun Microsystems.
FILES
- /etc/fstab
Static information about the file systems
- /etc/mnttab
Mounted file system table
SEE ALSO
fsclean(1M),
mount(1M),
quotaon(1M),
mount(2),
fstab(4),
mnttab(4),
pfs(4),
fs_wrapper(5),
memfs_bufcache_metapct(5),
memfs_bufcache_swappct(5),
quota(5).
STANDARDS CONFORMANCE
mount: SVID3
umount: SVID3
