mount.8

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(This can be meaningful with the
.B \-a
option.)

For example, the command:
.RS
.RS
.B "mount \-a \-t nomsdos,ext"
.RE
mounts all file systems except those of type
.I msdos
and
.IR ext .
.RE
.TP
.B \-O
Used in conjunction with
.BR \-a ,
to limit the set of filesystems to which the
.B \-a
is applied.  Like
.B \-t
in this regard except that it is useless except in the context of
.BR \-a .
For example, the command:
.RS
.RS
.B "mount \-a \-O no_netdev"
.RE
mounts all file systems except those which have the option
.I _netdev
specified in the options field in the
.I /etc/fstab
file.

It is different from
.B \-t
in that each option is matched exactly; a leading
.B no
at the beginning of one option does not negate the rest.

The
.B \-t
and
.B \-O
options are cumulative in effect; that is, the command
.RS
.B "mount \-a \-t ext2 \-O _netdev"
.RE
mounts all ext2 filesystems with the _netdev option, not all filesystems
that are either ext2 or have the _netdev option specified.
.RE
.TP
.B \-o
Options are specified with a
.B \-o
flag followed by a comma separated string of options.
Some of these options are only useful when they appear in the
.I /etc/fstab
file.  The following options apply to any file system that is being
mounted (but not every file system actually honors them - e.g., the
.B sync
option today has effect only for ext2, ext3 and ufs):
.RS
.TP
.B async
All I/O to the file system should be done asynchronously.
.TP
.B atime
Update inode access time for each access. This is the default.
.TP
.B auto
Can be mounted with the
.B \-a
option.
.TP
.B defaults
Use default options:
.BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async.
.TP
.B dev
Interpret character or block special devices on the file system.
.TP
.B exec
Permit execution of binaries.
.TP
.B group
Allow an ordinary (i.e., non-root) user to mount the file system if one
of his groups matches the group of the device.
This option implies the options
.BR nosuid " and " nodev
(unless overridden by subsequent options, as in the option line
.BR group,dev,suid ).
.TP
.B _netdev
The filesystem resides on a device that requires network access
(used to prevent the system from attempting to mount these filesystems
until the network has been enabled on the system).
.TP
.B noatime
Do not update inode access times on this file system (e.g, for faster
access on the news spool to speed up news servers).
.TP
.B noauto
Can only be mounted explicitly (i.e., the
.B \-a
option will not cause the file system to be mounted).
.TP
.B nodev
Do not interpret character or block special devices on the file
system.
.TP
.B noexec
Do not allow direct execution of any binaries on the mounted file system.
(Until recently it was possible to run binaries anyway using a command like
/lib/ld*.so /mnt/binary. This trick fails since Linux 2.4.25 / 2.6.0.)
.TP
.B nosuid
Do not allow set-user-identifier or set-group-identifier bits to take
effect. (This seems safe, but is in fact rather unsafe if you have
suidperl(1) installed.)
.TP
.B nouser
Forbid an ordinary (i.e., non-root) user to mount the file system.
This is the default.
.TP
.B owner
Allow an ordinary (i.e., non-root) user to mount the file system if he
is the owner of the device.
This option implies the options
.BR nosuid " and " nodev
(unless overridden by subsequent options, as in the option line
.BR owner,dev,suid ).
.TP
.B remount
Attempt to remount an already-mounted file system.  This is commonly
used to change the mount flags for a file system, especially to make a
readonly file system writeable. It does not change device or mount point.
.TP
.B ro
Mount the file system read-only.
.TP
.B rw
Mount the file system read-write.
.TP
.B suid
Allow set-user-identifier or set-group-identifier bits to take
effect.
.TP
.B sync
All I/O to the file system should be done synchronously.
.TP
.B dirsync
All directory updates within the file system should be done synchronously.
This affects the following system calls: creat, link, unlink, symlink,
mkdir, rmdir, mknod and rename.
.TP
.B user
Allow an ordinary user to mount the file system.
The name of the mounting user is written to mtab so that he can unmount
the file system again.
This option implies the options
.BR noexec ", " nosuid ", and " nodev
(unless overridden by subsequent options, as in the option line
.BR user,exec,dev,suid ).
.TP
.B users
Allow every user to mount and unmount the file system.
This option implies the options
.BR noexec ", " nosuid ", and " nodev
(unless overridden by subsequent options, as in the option line
.BR users,exec,dev,suid ).
.RE
.TP
.B \-\-bind
Remount a subtree somewhere else (so that its contents are available
in both places). See above.
.TP
.B \-\-move
Move a subtree to some other place. See above.

.SH "FILESYSTEM SPECIFIC MOUNT OPTIONS"
The following options apply only to certain file systems.
We sort them by file system. They all follow the
.B \-o
flag.
.SH "Mount options for adfs"
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
Set the owner and group of the files in the file system (default: uid=gid=0).
.TP
\fBownmask=\fP\fIvalue\fP and \fBothmask=\fP\fIvalue\fP
Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
respectively (default: 0700 and 0077, respectively).
See also
.IR /usr/src/linux/Documentation/filesystems/adfs.txt .
.SH "Mount options for affs"
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
Set the owner and group of the root of the file system (default: uid=gid=0,
but with option
.B uid
or
.B gid
without specified value, the uid and gid of the current process are taken).
.TP
\fBsetuid=\fP\fIvalue\fP and \fBsetgid=\fP\fIvalue\fP
Set the owner and group of all files.
.TP
.BI mode= value
Set the mode of all files to
.IR value " & 0777"
disregarding the original permissions.
Add search permission to directories that have read permission.
The value is given in octal.
.TP
.B protect
Do not allow any changes to the protection bits on the file system.
.TP
.B usemp
Set uid and gid of the root of the file system to the uid and gid
of the mount point upon the first sync or umount, and then
clear this option. Strange...
.TP
.B verbose
Print an informational message for each successful mount.
.TP
.BI prefix= string
Prefix used before volume name, when following a link.
.TP
.BI volume= string
Prefix (of length at most 30) used before '/' when following a symbolic link.
.TP
.BI reserved= value
(Default: 2.) Number of unused blocks at the start of the device.
.TP
.BI root= value
Give explicitly the location of the root block.
.TP
.BI bs= value
Give blocksize. Allowed values are 512, 1024, 2048, 4096.
.TP
.BR grpquota " / " noquota " / " quota " / " usrquota
These options are accepted but ignored.
(However, quota utilities may react to such strings in
.IR /etc/fstab .)

.SH "Mount options for coherent"
None.

.SH "Mount options for devpts"
The devpts file system is a pseudo file system, traditionally mounted on
.IR /dev/pts .
In order to acquire a pseudo terminal, a process opens
.IR /dev/ptmx ;
the number of the pseudo terminal is then made available to the process
and the pseudo terminal slave can be accessed as
.IR /dev/pts/ <number>.
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
This sets the owner or the group of newly created PTYs to
the specified values. When nothing is specified, they will
be set to the UID and GID of the creating process.
For example, if there is a tty group with GID 5, then
.B gid=5
will cause newly created PTYs to belong to the tty group.
.TP
.BI mode= value
Set the mode of newly created PTYs to the specified value.
The default is 0600.
A value of 
.B mode=620
and 
.B gid=5
makes "mesg y" the default on newly created PTYs.

.SH "Mount options for ext"
None.
Note that the `ext' file system is obsolete. Don't use it.
Since Linux version 2.1.21 extfs is no longer part of the kernel source.

.SH "Mount options for ext2"
The `ext2' file system is the standard Linux file system.
.\" Due to a kernel bug, it may be mounted with random mount options
.\" (fixed in Linux 2.0.4).
Since Linux 2.5.46, for most mount options the default
is determined by the filesystem superblock. Set them with
.BR tune2fs (8).
.TP
.BR bsddf " / " minixdf
Set the behaviour for the
.I statfs
system call. The
.B minixdf
behaviour is to return in the
.I f_blocks
field the total number of blocks of the file system, while the
.B bsddf
behaviour (which is the default) is to subtract the overhead blocks
used by the ext2 file system and not available for file storage. Thus
.RE
.nf

% mount /k -o minixdf; df /k; umount /k
Filesystem   1024-blocks  Used Available Capacity Mounted on
/dev/sda6      2630655   86954  2412169      3%   /k
% mount /k -o bsddf; df /k; umount /k
Filesystem   1024-blocks  Used Available Capacity Mounted on
/dev/sda6      2543714      13  2412169      0%   /k

.fi
(Note that this example shows that one can add command line options
to the options given in
.IR /etc/fstab .)

.TP
.\" Before Linux 2.3.99-pre3:
.\" .BR check " / " check=normal " / " check=strict
.\" Set checking level. When at least one of these options is set (and
.\" .B check=normal
.\" is set by default) the inodes and blocks bitmaps are checked upon mount
.\" (which can take half a minute or so on a big disk, and is rather useless).
.\" With strict checking, block deallocation checks that the block to free
.\" is in the data zone.
.\" Since 2.3.99-pre3 but before 2.6.0-test7 every string check=foo
.\" was equivalent to just check. Since 2.6.0-test7 only check is accepted.
.BR check
Check filesystem (block and inode bitmaps) at mount time.
.\" requires CONFIG_EXT2_CHECK
.TP
.BR check=none " / " nocheck
No checking is done at mount time. This is the default. This is fast.
It is wise to invoke
.BR e2fsck (8)
every now and then, e.g. at boot time.
.TP
.B debug
Print debugging info upon each (re)mount.
.TP
.BR 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 set in the filesystem superblock, and can be
changed using
.BR tune2fs (8).
.TP
.BR grpid " or " bsdgroups " / " nogrpid " or " sysvgroups
These options define what group id a newly created file gets.
When
.BR grpid
is set, it takes the group id of the directory in which it is created;
otherwise (the default) it takes the fsgid of the current process, unless
the directory has the setgid bit set, in which case it takes the gid
from the parent directory, and also gets the setgid bit set
if it is a directory itself.
.TP
.BR nobh
Do not attach buffer_heads to file pagecache. (Since 2.5.49.)
.TP
.BR nouid32
Disables 32-bit UIDs and GIDs.  This is for interoperability with older
kernels which only store and expect 16-bit values.
.TP
.BR oldalloc " or " orlov
Use old allocator or Orlov allocator for new inodes. Orlov is default.
.TP
\fBresgid=\fP\fIn\fP and \fBresuid=\fP\fIn\fP
The ext2 file system reserves a certain percentage of the available
space (by default 5%, see
.BR mke2fs (8)
and
.BR tune2fs (8)).
These options determine who can use the reserved blocks.
(Roughly: whoever has the specified uid, or belongs to the specified group.)
.TP
.BI sb= n
Instead of block 1, use block
.I n
as superblock. This could be useful when the filesystem has been damaged.
(Earlier, copies of the superblock would be made every 8192 blocks: in
block 1, 8193, 16385, ... (and one got thousands of copies on
a big filesystem). Since version 1.08,
.B mke2fs
has a \-s (sparse superblock) option to reduce the number of backup
superblocks, and since version 1.15 this is the default. Note
that this may mean that ext2 filesystems created by a recent
.B mke2fs
cannot be mounted r/w under Linux 2.0.*.)
The block number here uses 1k units. Thus, if you want to use logical
block 32768 on a filesystem with 4k blocks, use "sb=131072".
.TP
.BR user_xattr " / " nouser_xattr
Support "user." extended attributes (or not).
.\" requires CONFIG_EXT2_FS_XATTR
.TP
.BR acl " / " noacl
Support POSIX Access Control Lists (or not).
.\" requires CONFIG_EXT2_FS_POSIX_ACL
.TP
.BR grpquota " / " noquota " / " quota " / " usrquota
These options are accepted but ignored.


.SH "Mount options for ext3"
The `ext3' file system is version of the ext2 file system which has been
enhanced with journalling.  It supports the same options as ext2 as
well as the following additions:
.\" .TP
.\" .BR abort
.\" Mount the file system in abort mode, as if a fatal error has occurred.
.TP
.BR journal=update
Update the ext3 file system's journal to the current format.
.TP
.BR journal=inum
When a journal already exists, this option is ignored. Otherwise, it
specifies the number of the inode which will represent the ext3 file system's
journal file;  ext3 will create a new journal, overwriting the old contents
of the file whose inode number is
.IR inum .
.TP
.BR noload
Do not load the ext3 file system's journal on mounting.
.TP
.BR data=journal " / " data=ordered " / " data=writeback
Specifies the journalling mode for file data.  Metadata is always journaled.
.RS
.TP
.B journal
All data is committed into the journal prior to being written into the
main file system.
.TP
.B ordered
This is the default mode.  All data is forced directly out to the main file
system prior to its metadata being committed to the journal.
.TP
.B writeback
Data ordering is not preserved - data may be written into the main
file system after its metadata has been committed to the journal.
This is rumoured to be the highest-throughput option.  It guarantees
internal file system integrity, however it can allow old data to appear
in files after a crash and journal recovery.
 
.SH "Mount options for fat"
(Note:
.I fat
is not a separate filesystem, but a common part of the
.IR msdos ,
.I umsdos
and
.I vfat
filesystems.)
.TP
.BR blocksize=512 " / " blocksize=1024 " / " blocksize=2048
Set blocksize (default 512).
.TP
\fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
Set the owner and group of all files. (Default: the uid and gid
of the current process.)
.TP
.BI umask= value
Set the umask (the bitmask of the permissions that are
.B not
present). The default is the umask of the current process.
The value is given in octal.
.TP
.BI dmask= value
Set the umask applied to directories only.
The default is the umask of the current process.
The value is given in octal. Present since 2.5.43.