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

NAME
     mountmount file systems

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

DESCRIPTION
     The mount utility calls the nmount(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
     appropriate information is taken from the fstab(5) file.

     The system maintains a list of currently mounted file systems.  If no
     arguments 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”
	     (unless 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
	     options are available:

	     acls    Enable POSIX.1e Access Control Lists, or ACLs, which can
		     be customized via the setfacl(1) and getfacl(1) commands.
		     This flag is mutually exclusive with nfsv4acls flag.

	     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
		     remain consistent.	 For this reason, the async flag
		     should be used sparingly, and only when some data recov‐
		     ery mechanism is present.

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

	     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.

	     mountprog=⟨program⟩
		     Force mount to use the specified program to mount the
		     file system, instead of calling nmount(2) directly.  For
		     example:

		     mount -t foofs -o mountprog=/mydir/fooprog /dev/acd0 /mnt

	     multilabel
		     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
		     automatically at mount-time.

	     nfsv4acls
		     Enable NFSv4 ACLs, which can be customized via the
		     setfacl(1) and getfacl(1) commands.  This flag is mutu‐
		     ally exclusive with acls flag.

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

	     noatime
		     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.

	     noclusterr
		     Disable read clustering.

	     noclusterw
		     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.

	     nosymfollow
		     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).

	     snapshot
		     This option allows a snapshot of the specified file sys‐
		     tem to be taken.  The -u flag is required with this
		     option.  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
		     unmount 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
		     order, however you may not get back all the space con‐
		     tained 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
		     snapshot 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
			  appear as zero length files.	When you are done with
			  the mounted snapshot:

			  umount /mnt
			  mdconfig -d -u 4

	     suiddir
		     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.
		     Execute 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.

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

	     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 cd9660 -o -e /dev/cd0 /cdrom

	     causes mount to execute the equivalent of:

		   /sbin/mount_cd9660 -e /dev/cd0 /cdrom

	     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
	     option.

     -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.

	     The default behavior of mount is to pass the -t option directly
	     to the nmount(2) system call in the fstype option.

	     However, for the following file system types: cd9660, mfs,
	     msdosfs, newnfs, nfs, ntfs, nwfs, nullfs, portalfs, smbfs, udf,
	     and unionfs, mount will not call nmount(2) directly and will
	     instead attempt to execute a program in /sbin/mount_XXX where XXX
	     is replaced by the file system 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
	     options specified in the argument to -o and finally applying the
	     -r or -w option.

     -v	     Verbose mode.  If the -v is used alone, show all file systems,
	     including those that were mounted with the MNT_IGNORE flag and
	     show additional information about each file system (including
	     fsid when run by root).

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

ENVIRONMENT
     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
		 information.)

FILES
     /etc/fstab	 file system table

DIAGNOSTICS
     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
     kldload(8)).

SEE ALSO
     getfacl(1), setfacl(1), nmount(2), acl(3), mac(4), devfs(5), ext2fs(5),
     fstab(5), procfs(5), kldload(8), mount_cd9660(8), mount_msdosfs(8),
     mount_nfs(8), mount_ntfs(8), mount_nullfs(8), mount_nwfs(8),
     mount_portalfs(8), mount_smbfs(8), mount_udf(8), mount_unionfs(8),
     umount(8), zfs(8), zpool(8)

CAVEATS
     After a successful mount, the permissions on the original mount point
     determine 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).

     Use of the mount is preferred over the use of the file system specific
     mount_XXX commands.  In particular, mountd(8) gets a SIGHUP signal (that
     causes an update of the export list) only when the file system is mounted
     via mount.

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

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

BSD			       February 10, 2010			   BSD
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