MirOS Manual: mount(8)

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


     mount - mount file systems


     mount [-Aadfruvw] [-t type]
     mount [-dfruvw] special | node
     mount [-dfruvw] [-o options] [-t type] special node


     The mount command invokes a file system specific program to prepare and
     graft the special device or remote node (rhost:path) on to the file sys-
     tem tree at the point node. If either special or node are not provided,
     the appropriate information is taken from the fstab(5) file.

     For disk partitions, the special device must correspond to a partition
     registered in the disklabel(5).

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

     A mount point node must be an existing directory for a mount to succeed
     (except in the special case of /, of course). Only the superuser may
     mount file systems unless kern.usermount is nonzero (see sysctl(8)), the
     special device is readable and writeable by the user attempting the
     mount, and the mount point node is owned by the user attempting the

     The options are as follows:

     -A      Causes mount to try to mount all of the file systems listed in
             the fstab(5) table except those for which the "noauto" option is

     -a      Similar to the -A flag, except that if a file system (other than
             the root file system) appears to be already mounted, mount will
             not try to mount it again. mount assumes that a file system is
             already mounted if a file system with the same type is mounted on
             the given mount point. More stringent checks are not possible be-
             cause some file system types report strange values for the
             mounted-from device for mounted file systems.

     -d      Causes everything to be done except for the invocation of the
             file system specific program. This option is useful in conjunc-
             tion with the -v flag to determine what the mount command is try-
             ing to do.

     -f      Either force mounting of dirty file systems or, in the case of a
             downgrade from read-write to read-only operation, the revocation
             of opened files with write access.

     -o options
             Options can be given with (or without) a 'no' prefix to invert
             their meaning. The options listed below specify non-default
             values. For example, 'noasync' is the default, so 'async' can be
             used to mount a file system asynchronously. Multiple options can
             be specified in a comma-separated list. The available options are
             as follows:

             async   All I/O to the file system should be done asynchronously.
                     This is a dangerous flag to set since it does not guaran-
                     tee to keep a consistent file system structure on the
                     disk. You should not use this flag unless you are
                     prepared to recreate the file system should your system
                     crash. The most common use of this flag is to speed up
                     restore(8) where it can give a factor of two speed in-

                     (FFS only.) Mount the file system using soft dependen-
                     cies. Instead of metadata being written immediately, it
                     is written in an ordered fashion to keep the on-disk
                     state of the file system consistent. This results in sig-
                     nificant speedups for file create/delete operations. This
                     option will be ignored when using the -u flag and a file
                     system is already mounted read/write. It requires option
                     FFS_SOFTUPDATES to be enabled in the running kernel.

             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.

                     Do not update atime on files in the system unless the
                     mtime or ctime is being changed as well. This option is
                     useful for laptops and news servers where one does not
                     want the extra disk activity associated with updating the

                     Synonym for noatime provided for compatibility with other
                     operating systems.

             noauto  Do not mount the file system automatically (either at
                     boot or with the -A or -a options).

             nodev   Do not interpret character or block special devices on
                     the file system. This option is useful for a server that
                     has file systems containing special devices for architec-
                     tures other than its own.

             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.

             nosuid  Do not allow set-user-identifier or set-group-identifier
                     bits to take effect.

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

             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.

             Any additional options specific to a given file system type (see
             the -t option) may be passed as a comma separated list; these op-
             tions 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 mfs -o nosuid,-s=4000 /dev/sd0b /tmp

             causes mount to execute the equivalent of:

                   # /sbin/mount_mfs -o nosuid -s 4000 /dev/sd0b /tmp

     -r      The file system is to be mounted read-only. Mount the file system
             read-only (even the superuser may not write it). The same as the
             "rdonly" argument to the -o option.

     -t type
             The argument following the -t is used to indicate the file system
             type. The type ffs 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 com-
             ma separated list. The list of file system types can be prefixed
             with "no" to specify the file system types for which action
             should not be taken. For example, the mount command:

                   # mount -a -t nonfs,mfs

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

             mount will attempt to execute a program in /sbin/mount_XXX where
             XXX is replaced by the type name. For example, NFS file systems
             are mounted by the program /sbin/mount_nfs.

     -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 speci-
             fied. Only options specified on the command line with -o are
             changed; other file system options are unaltered. The options set
             in the fstab(5) table are ignored.

     -v      Verbose mode.

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

     The options specific to the various file system types are described in
     the manual pages for those file systems' mount_XXX commands. For in-
     stance, the options specific to Berkeley Fast File Systems are described
     in the mount_ffs(8) manual page.


     /etc/fstab  file system table


     Mount a CD-ROM on node /mnt/cdrom:

           # mount -t cd9660 -r /dev/cd0a /mnt/cdrom

     Mount an MS-DOS floppy on node /mnt/floppy:

           # mount -t msdos /dev/fd0a /mnt/floppy

     Graft a remote NFS file system on host host, path /path/name, on node

           # mount host:/path/name /mnt/nfs

     Remount /var with option "dev":

           # mount -u -o dev /var


     mount(2), fstab(5), disklabel(8), mount_ados(8), mount_cd9660(8),
     mount_ext2fs(8), mount_fdesc(8), mount_ffs(8), mount_kernfs(8),
     mount_mfs(8), mount_msdos(8), mount_nfs(8), mount_ntfs(8),
     mount_portal(8), mount_procfs(8), mount_udf(8), mount_xfs(8), sysctl(8),


     A mount command appeared in Version 3 AT&T UNIX.


     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).

MirOS BSD #10-current           March 27, 1994                               3

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