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MOUNT(8)		  BSD System Manager's Manual		      MOUNT(8)

     mount -- mount file systems

     mount [-adflpruvw]	[-F fstab] [-o options]	[-t ufs	| external_type]
     mount [-dfpruvw] special |	node
     mount [-dfpruvw] [-o options] [-t ufs | external_type] special node

     The mount utility calls the mount(2) system call to prepare and graft a
     special device or the remote node (rhost:path) on to the file system tree
     at	the point node.	 If either special or node are not provided, the ap-
     propriate information is taken from the fstab(5) file.

     The system	maintains a list of currently mounted file systems.  If	no ar-
     guments are given to mount, this list is printed.

     The options are as	follows:

     -a	     All the file systems described in fstab(5)	are mounted.  Excep-
	     tions are those marked as "noauto", those marked as "late"	(un-
	     less the -l option	was specified),	those excluded by the -t flag
	     (see below), or if	they are already mounted (except the root file
	     system which is always remounted to preserve traditional single
	     user mode behavior).

     -d	     Causes everything to be done except for the actual	system call.
	     This option is useful in conjunction with the -v flag to deter-
	     mine what the mount command is trying to do.

     -F	fstab
	     Specify the fstab file to use.

     -f	     Forces the	revocation of write access when	trying to downgrade a
	     file system mount status from read-write to read-only.  Also
	     forces the	R/W mount of an	unclean	file system (dangerous;	use
	     with caution).

     -l	     When used in conjunction with the -a option, also mount those
	     file systems which	are marked as "late".

     -o	     Options are specified with	a -o flag followed by a	comma sepa-
	     rated string of options.  In case of conflicting options being
	     specified,	the rightmost option takes effect.  The	following op-
	     tions are available:

	     acls    Enable Access Control Lists, or ACLS, which can be	cus-
		     tomized via the setfacl(1)	and getfacl(1) commands.

	     async   All I/O to	the file system	should be done asynchronously.
		     This is a dangerous flag to set, since it does not	guar-
		     antee that	the file system	structure on the disk will re-
		     main consistent.  For this	reason,	the async flag should
		     be	used sparingly,	and only when some data	recovery mech-
		     anism is present.

		     When used with the	-u flag, this is the same as specify-
		     ing the options currently in effect for the mounted file

	     force   The same as -f; forces the	revocation of write access
		     when trying to downgrade a	file system mount status from
		     read-write	to read-only.  Also forces the R/W mount of an
		     unclean file system (dangerous; use with caution).

	     fstab   When used with the	-u flag, this is the same as specify-
		     ing all the options listed	in the fstab(5)	file for the
		     file system.

	     late    This file system should be	skipped	when mount is run with
		     the -a flag but without the -l flag.

		     Enable multi-label	Mandatory Access Control, or MAC, on
		     the specified file	system.	 If the	file system supports
		     multilabel	operation, individual labels will be main-
		     tained for	each object in the file	system,	rather than
		     using a single label for all objects.  An alternative to
		     the -l flag in tunefs(8).	See mac(4) for more informa-
		     tion, which cause the multilabel mount flag to be set au-
		     tomatically at mount-time.

		     Metadata I/O should be done synchronously,	while data I/O
		     should be done asynchronously.  This is the default.

		     Do	not update the file access time	when reading from a
		     file.  This option	is useful on file systems where	there
		     are large numbers of files	and performance	is more	criti-
		     cal than updating the file	access time (which is rarely
		     ever important).  This option is currently	only supported
		     on	local file systems.

	     noauto  This file system should be	skipped	when mount is run with
		     the -a flag.

		     Disable read clustering.

		     Disable write clustering.

	     noexec  Do	not allow execution of any binaries on the mounted
		     file system.  This	option is useful for a server that has
		     file systems containing binaries for architectures	other
		     than its own.  Note: This option was not designed as a
		     security feature and no guarantee is made that it will
		     prevent malicious code execution; for example, it is
		     still possible to execute scripts which reside on a
		     noexec mounted partition.

	     nosuid  Do	not allow set-user-identifier or set-group-identifier
		     bits to take effect.  Note: this option is	worthless if a
		     public available suid or sgid wrapper like	suidperl(1) is
		     installed on your system.	It is set automatically	when
		     the user does not have super-user privileges.

		     Do	not follow symlinks on the mounted file	system.

	     ro	     The same as -r; mount the file system read-only (even the
		     super-user	may not	write it).

	     sync    All I/O to	the file system	should be done synchronously.

		     This option allows	a snapshot of the specified file sys-
		     tem to be taken.  The -u flag is required with this op-
		     tion.  Note that snapshot files must be created in	the
		     file system that is being snapshotted.  You may create up
		     to	20 snapshots per file system.  Active snapshots	are
		     recorded in the superblock, so they persist across	un-
		     mount and remount operations and across system reboots.
		     When you are done with a snapshot,	it can be removed with
		     the rm(1) command.	 Snapshots may be removed in any or-
		     der, however you may not get back all the space contained
		     in	the snapshot as	another	snapshot may claim some	of the
		     blocks that it is releasing.  Note	that the schg flag is
		     set on snapshots to ensure	that not even the root user
		     can write to them.	 The unlink command makes an exception
		     for snapshot files	in that	it allows them to be removed
		     even though they have the schg flag set, so it is not
		     necessary to clear	the schg flag before removing a	snap-
		     shot file.

		     Once you have taken a snapshot, there are three interest-
		     ing things	that you can do	with it:

		     1.	  Run fsck(8) on the snapshot file.  Assuming that the
			  file system was clean	when it	was mounted, you
			  should always	get a clean (and unchanging) result
			  from running fsck on the snapshot.  This is essen-
			  tially what the background fsck process does.

		     2.	  Run dump(8) on the snapshot.	You will get a dump
			  that is consistent with the file system as of	the
			  timestamp of the snapshot.

		     3.	  Mount	the snapshot as	a frozen image of the file
			  system.  To mount the	snapshot /var/snapshot/snap1:

			  mdconfig -a -t vnode -f /var/snapshot/snap1 -u 4
			  mount	-r /dev/md4 /mnt

			  You can now cruise around your frozen	/var file sys-
			  tem at /mnt.	Everything will	be in the same state
			  that it was at the time the snapshot was taken.  The
			  one exception	is that	any earlier snapshots will ap-
			  pear as zero length files.  When you are done	with
			  the mounted snapshot:

			  umount /mnt
			  mdconfig -d -u 4

			  Further details can be found in the file at

		     A directory on the	mounted	file system will respond to
		     the SUID bit being	set, by	setting	the owner of any new
		     files to be the same as the owner of the directory.  New
		     directories will inherit the bit from their parents.  Ex-
		     ecute bits	are removed from the file, and it will not be
		     given to root.

		     This feature is designed for use on fileservers serving
		     PC	users via ftp, SAMBA, or netatalk.  It provides	secu-
		     rity holes	for shell users	and as such should not be used
		     on	shell machines,	especially on home directories.	 This
		     option requires the SUIDDIR option	in the kernel to work.
		     Only UFS file systems support this	option.	 See chmod(2)
		     for more information.

	     update  The same as -u; indicate that the status of an already
		     mounted file system should	be changed.

	     union   Causes the	namespace at the mount point to	appear as the
		     union of the mounted file system root and the existing
		     directory.	 Lookups will be done in the mounted file sys-
		     tem first.	 If those operations fail due to a non-exis-
		     tent file the underlying directory	is then	accessed.  All
		     creates are done in the mounted file system.

	     Any additional options specific to	a file system type that	is not
	     one of the	internally known types (see the	-t option) may be
	     passed as a comma separated list; these options are distinguished
	     by	a leading "-" (dash).  Options that take a value are specified
	     using the syntax -option=value.  For example, the mount command:

		   mount -t unionfs -o -b /sys $HOME/sys

	     causes mount to execute the equivalent of:

		   /sbin/mount_unionfs -b /sys $HOME/sys

	     Additional	options	specific to file system	types which are	not
	     internally	known (see the description of the -t option below) may
	     be	described in the manual	pages for the associated
	     /sbin/mount_XXX utilities.

     -p	     Print mount information in	fstab(5) format.  Implies also the -v

     -r	     The file system is	to be mounted read-only.  Mount	the file sys-
	     tem read-only (even the super-user	may not	write it).  The	same
	     as	the ro argument	to the -o option.

     -t	ufs | external_type
	     The argument following the	-t is used to indicate the file	system
	     type.  The	type ufs is the	default.  The -t option	can be used to
	     indicate that the actions should only be taken on file systems of
	     the specified type.  More than one	type may be specified in a
	     comma separated list.  The	list of	file system types can be pre-
	     fixed with	"no" to	specify	the file system	types for which	action
	     should not	be taken.  For example,	the mount command:

		   mount -a -t nonfs,nullfs

	     mounts all	file systems except those of type NFS and NULLFS.

	     If	the type is not	one of the internally known types, mount will
	     attempt to	execute	a program in /sbin/mount_XXX where XXX is re-
	     placed by the type	name.  For example, nfs	file systems are
	     mounted by	the program /sbin/mount_nfs.

	     Most file systems will be dynamically loaded by the kernel	if not
	     already present, and if the kernel	module is available.

     -u	     The -u flag indicates that	the status of an already mounted file
	     system should be changed.	Any of the options discussed above
	     (the -o option) may be changed; also a file system	can be changed
	     from read-only to read-write or vice versa.  An attempt to	change
	     from read-write to	read-only will fail if any files on the	file
	     system are	currently open for writing unless the -f flag is also
	     specified.	 The set of options is determined by applying the op-
	     tions specified in	the argument to	-o and finally applying	the -r
	     or	-w option.

     -v	     Verbose mode.

     -w	     The file system object is to be read and write.

     PATH_FSTAB	 If the	environment variable PATH_FSTAB	is set,	all operations
		 are performed against the specified file.  PATH_FSTAB will
		 not be	honored	if the process environment or memory address
		 space is considered "tainted".	 (See issetugid(2) for more

     /etc/fstab	 file system table

     Various, most of them are self-explanatory.

	   XXXXX file system is	not available

     The kernel	does not support the respective	file system type.  Note	that
     support for a particular file system might	be provided either on a	static
     (kernel compile-time), or dynamic basis (loaded as	a kernel module	by

     getfacl(1), setfacl(1), mount(2), acl(3), mac(4), fstab(5), kldload(8),
     mount_cd9660(8), mount_devfs(8), mount_ext2fs(8), mount_fdescfs(8),
     mount_linprocfs(8), mount_msdosfs(8), mount_nfs(8), mount_ntfs(8),
     mount_nullfs(8), mount_nwfs(8), mount_portalfs(8),	mount_procfs(8),
     mount_reiserfs(8),	mount_smbfs(8),	mount_std(8), mount_udf(8),
     mount_umapfs(8), mount_unionfs(8),	umount(8)

     After a successful	mount, the permissions on the original mount point de-
     termine if	.. is accessible from the mounted file system.	The minimum
     permissions for the mount point for traversal across the mount point in
     both directions to	be possible for	all users is 0111 (execute for all).

     A mount utility appeared in Version 1 AT&T	UNIX.

     It	is possible for	a corrupted file system	to cause a crash.

BSD				 July 12, 2006				   BSD


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