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MOUNT(8) NetBSD System Manager's Manual MOUNT(8)
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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. The provided argument is looked up
first in the ``fs_file'', then in the ``fs_spec'' column. If the match-
ing entry in fstab(5) has the string ``from_mount'' as its ``fs_spec''
field, the device or remote file system already mounted at the location
specified by ``fs_spec'' will be used.
If both special and node are given, the disklabel is checked for the file
In NetBSD, a file system can only be mounted by an ordinary user who owns
the point node and has access to the special device (at least read per-
missions). Also, the vfs.generic.usermount sysctl(3) must be set to 1 to
permit file system mounting by ordinary users, see sysctl(8). Finally,
the flags nosuid and nodev must be given for non-superuser mounts.
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 Causes mount to try to mount all of the file systems listed in
the fstab(5) file 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
because 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 Forces the revocation of write access when trying to downgrade a
file system mount status from read-write to read-only.
-o Options are specified with a -o flag followed by a comma sepa-
rated string of options. The following options are available:
async All I/O to the file system should be done asyn-
chronously. In the event of a crash, it is
impossible for the system to verify the integrity of
data on a file system mounted with this option. You
should only use this option if you have an applica-
tion-specific data recovery mechanism, or are willing
to recreate the file system from scratch.
noasync Clear async mode.
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.
getargs Retrieves the file system specific mount arguments
for the given mounted file system and prints them.
hidden By setting the MNT_IGNORE flag, causes the mount
point to be excluded from the list of file systems
shown by default with df(1).
noatime Never update the access time field for files. This
option is useful for optimizing read performance on
file systems that are used as news spools.
noauto This file system should be skipped when mount is run
with the -a flag.
nocoredump Do not allow programs to create crash dumps (core
files) on the file system. This option can be used
to help protect sensitive data by keeping core files
(which may contain sensitive data) from being created
on insecure file systems. Only core files that would
be created by program crashes are prevented by use of
this flag; the behavior of savecore(8) is not
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 architectures other than its own.
nodevmtime Do not update modification times on device special
files. This option is useful on laptops or other
systems that perform power management.
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 architec-
tures other than its own.
nosuid Do not allow set-user-identifier or set-group-identi-
fier bits to take effect.
port (NFS only) Use the specified NFS port.
rdonly The same as -r; mount the file system read-only (even
the super-user may not write it).
reload Reload all incore data for a file system. This is
used mainly after running fsck(8) on the root file
system and finding things to fix. The file system
must be mounted read-only. All cached meta-data are
invalidated, superblock and summary information is
re-read from disk, all cached inactive vnodes and
file data are invalidated and all inode data are re-
read for all active vnodes.
softdep (FFS only) Mount the file system using soft dependen-
cies. This means that metadata will not be written
immediately, but is written in an ordered fashion to
keep the on-disk state of the file system consistent.
This results in significant speedups for file cre-
ate/delete operations. This option will be ignored
when using the -u flag and a file system is already
mounted read/write. This option has gone through
moderate to heavy testing, but should still be used
with care. A file system mounted with softdep can
not be mounted with async. It requires the SOFTDEP
option to be enabled in the running kernel.
symperm Recognize permission of symbolic link when reading or
sync All I/O to the file system should be done syn-
chronously. This is not equivalent to the normal
mode in which only metadata is written synchronously.
nosync Clear sync mode.
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 system first. If those operations fail
due to a non-existent file the underlying directory
is then accessed. All creates are done in the
mounted file system, except for the fdesc file sys-
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
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 mfs -o nosuid,-N,-s=32m swap /tmp
causes mount to execute the equivalent of:
/sbin/mount_mfs -o nosuid -N -s 32m swap /tmp
-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 ``rdonly'' argument to the -o option.
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
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,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
specified. The set of options is determined by first extracting
the options for the file system from the fstab(5) file, then
applying any options specified by the -o argument, and finally
applying the -r or -w option.
-v Verbose mode. If this flag is specified more than once, then the
file system-specific mount arguments are printed for the given
mounted file system.
-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
instance the options specific to Berkeley Fast File System (FFS) are
described in the mount_ffs(8) manual page.
The particular type of file system in each partition of a disk can be
found by examining the disk label with the disklabel(8) command.
/etc/fstab file system table
Some useful examples:
mount -t cd9660 -r /dev/cd0a /cdrom
mount -t msdos /dev/fd0a /floppy
mount nfs-server-host:/directory/path /mount-point
MFS (32 megabyte)
mount -t mfs -o nosuid,-s=32m swap /tmp
The ``noauto'' directive in /etc/fstab can be used to make it easy to
manually mount and unmount removable media using just the mountpoint
filename, with an entry like this:
/dev/cd0a /cdrom cd9660 ro,noauto 0 0
That would allow a simple command like "mount /cdrom" or "umount /cdrom"
for media using the ISO-9660 file system format in the first CD-ROM
The error ``Operation not supported by device'' indicates that the mount
for the specified file-system type cannot be completed because the kernel
lacks support for the said file-system. See options(4).
df(1), mount(2), options(4), fstab(5), disklabel(8), fsck(8),
mount_ados(8), mount_cd9660(8), mount_ext2fs(8), mount_fdesc(8),
mount_ffs(8), mount_filecore(8), mount_kernfs(8), mount_lfs(8),
mount_mfs(8), mount_msdos(8), mount_nfs(8), mount_ntfs(8), mount_null(8),
mount_overlay(8), mount_portal(8), mount_procfs(8), mount_udf(8),
mount_umap(8), mount_union(8), umount(8)
A mount command appeared in Version 6 AT&T UNIX.
NetBSD 4.0 August 1, 2007 NetBSD 4.0