NAME
mount, umount - mount and unmount file systems
SYNOPSIS
/usr/etc/mount [ -p ]
/usr/etc/mount -a [ fnv ] [ -t type ]
/usr/etc/mount [ -fnrv ] [ -t type ] [ -o options ] filesys-
tem directory
/usr/etc/mount [ -vfn ] [ -o options ] filesystem | direc-
tory
/usr/etc/mount -d [ fnvr ] [ -o options ] RFS-resource |
directory
/usr/etc/umount [ -t type ] [ -h host ]
/usr/etc/umount -a [ v ]
/usr/etc/umount [ -v ] filesystem|directory ...
/usr/etc/umount [ -d ] RFS-resource | directory
DESCRIPTION
mount attaches a named filesystem to the file system hierar-
chy at the pathname location directory, which must already
exist. If directory has any contents prior to the mount
operation, these remain hidden until the filesystem is once
again unmounted. If filesystem is of the form
host:pathname, it is assumed to be an NFS file system (type
nfs).
umount unmounts a currently mounted file system, which can
be specified either as a directory or a filesystem.
mount and umount maintain a table of mounted file systems in
/etc/mtab, described in fstab(5). If invoked without an
argument, mount displays the contents of this table. If
invoked with either a filesystem or directory only, mount
searches the file /etc/fstab for a matching entry, and
mounts the file system indicated in that entry on the indi-
cated directory.
mount also allows the creation of new, virtual file systems
using loopback mounts. Loopback file systems provide access
to existing files using alternate pathnames. Once a virtual
file system is created, other file systems can be mounted
within it without affecting the original file system. File
systems that are subsequently mounted onto the original file
system, however, are visible to the virtual file system,
unless or until the corresponding mount point in the virtual
file system is covered by a file system mounted there.
Recursive traversal of loopback mount points is not allowed;
after the loopback mount of /tmp/newroot, the file
/tmp/newroot/tmp/newroot does not contain yet another file
system hierarchy. Rather, it appears just as /tmp/newroot
did before the loopback mount was performed (say, as an
empty directory).
The standard RC files first perform 4.2 mounts, then nfs
mounts, during booting. On Sun386i systems, lo (loopback)
mounts are performed just after 4.2 mounts. /etc/fstab
files depending on alternate mount orders at boot time will
fail to work as expected. Manual modification of
/etc/rc.local will be needed to make such mount orders work.
See lofs(4S) and fstab(5) for more information and WARNINGS
about loopback mounts.
OPTIONS
mount
-p Print the list of mounted file systems in a format
suitable for use in /etc/fstab.
-a All. Attempt to mount all the file systems described
in /etc/fstab. If a type argument is specified with
-t, mount all file systems of that type. Using -a,
mount builds a dependency tree of mount points in
/etc/fstab. mount will correctly mount these file sys-
tems regardless of their order in /etc/fstab (except
loopback mounts; see WARNINGS below).
-f Fake an /etc/mtab entry, but do not actually mount any
file systems.
-n Mount the file system without making an entry in
/etc/mtab.
-v Verbose. Display a message indicating each file system
being mounted.
-t type
Specify a file system type. The accepted types are
4.2, nfs, rfs, lo, hsfs, and tmp. See fstab(5) for a
description of 4.2, hsfs, and nfs; see lofs(4S) for a
description of lo; and see tmpfs(4) for a description
of tmp. See System and Network Administration for
details on rfs.
-r Mount the specified file system read-only, even if the
entry in /etc/fstab specifies that it is to be mounted
read-write.
Physically write-protected and magnetic-tape file sys-
tems must be mounted read-only. Otherwise errors occur
when the system attempts to update access times, even
if no write operation is attempted.
-d Mount an RFS file system. This option provides compati-
bility with the System V, Release 3 syntax for RFS
mounts. Alternatively, the equivalent Sun syntax, -t
rfs, may be used.
-o options
Specify file system options, a comma-separated list of
words from the list below. Some options are valid for
all file system types, while others apply to a specific
type only.
options valid on all file systems:
rw|ro Read/write or read-only.
suid|nosuid Setuid execution allowed or disal-
lowed.
grpid Create files with BSD semantics for
the propagation of the group ID.
Under this option, files inherit the
GID of the directory in which they
are created, regardless of the
directory's set-GID bit.
noauto Do not mount this file system that
is currently mounted read-only. If
the file system is not currently
mounted, an error results.
remount If the file system is currently
mounted, and if the entry in
/etc/fstab specifies that it is to
be mounted read-write or rw was
specified along with remount,
remount the file system making it
read-write. If the entry in
/etc/fstab specifies that it is to
be mounted read-only and rw was not
specified, the file system is not
remounted. If the file system is
currently mounted read-write, speci-
fying ro along with remount results
in an error. If the file system is
not currently mounted, an error
results.
The default is `rw,suid'.
options specific to 4.2 file systems:
quota|noquota Usage limits are enforced, or are
not enforced. The default is
noquota.
options specific to nfs (NFS) file systems:
bg|fg If the first attempt fails, retry in
the background, or, in the fore-
ground.
noquota Prevent quota(1) from checking
whether the user is over quota on
this file system; if the file system
has quotas enabled on the server,
quotas will still be checked for
operations on this file system.
retry=n The number of times to retry the
mount operation.
rsize=n Set the read buffer size to n bytes.
wsize=n Set the write buffer size to n
bytes.
timeo=n Set the NFS timeout to n tenths of a
second.
retrans=n The number of NFS retransmissions.
port=n The server IP port number.
soft|hard Return an error if the server does
not respond, or continue the retry
request until the server responds.
intr Allow keyboard interrupts on hard
mounts.
secure Use a more secure protocol for NFS
transactions.
posix Request POSIX.1 semantics for the
file system. Requires a mount ver-
sion 2 mountd(8C) on the server.
acregmin=n Hold cached attributes for at least
n seconds after file modification.
acregmax=n Hold cached attributes for no more
than n seconds after file modifica-
tion.
acdirmin=n Hold cached attributes for at least
n seconds after directory update.
acdirmax=n Hold cached attributes for no more
than n seconds after directory
update.
actimeo=n Set min and max times for regular
files and directories to n seconds.
nocto Suppress fresh attributes when open-
ing a file.
noac Suppress attribute and name (lookup)
caching.
Regular defaults are:
fg,retry=10000,timeo=7,retrans=3,port=NFS_PORT,hard,\
acregmin=3,acregmax=60,acdirmin=30,acdirmax=60
actimeo has no default; it sets acregmin, acreg-
max, acdirmin and acdirmax
Defaults for rsize and wsize are set internally by
the system kernel.
options specific to rfs (RFS) file systems:
bg|fg If the first attempt fails, retry in
the background, or, in the fore-
ground.
retry=n The number of times to retry the
mount operation.
Defaults are the same as for NFS.
options specific to hsfs (HSFS) file systems:
norrip Disable processing of Rock Ridge
extensions for the file system.
umount
-h host
Unmount all file systems listed in /etc/mtab that are
remote-mounted from host.
-t type
Unmount all file systems listed in /etc/mtab that are
of a given type.
-a Unmount all file systems currently mounted (as listed
in /etc/mtab).
-v Verbose. Display a message indicating each file system
being unmounted.
-d Unmount an RFS file system. This option provides com-
patibility with the System V, Release 3 syntax for
unmounting an RFS file system.
NFS FILESYSTEMS
Background vs. Foreground
Filesystems mounted with the bg option indicate that mount
is to retry in the background if the server's mount daemon
(mountd(8C)) does not respond. mount retries the request up
to the count specified in the retry=n option. Once the file
system is mounted, each NFS request made in the kernel waits
timeo=n tenths of a second for a response. If no response
arrives, the time-out is multiplied by 2 and the request is
retransmitted. When the number of retransmissions has
reached the number specified in the retrans=n option, a file
system mounted with the soft option returns an error on the
request; one mounted with the hard option prints a warning
message and continues to retry the request.
Read-Write vs. Read-Only
File systems that are mounted rw (read-write) should use the
hard option.
Interrupting Processes With Pending NFS Requests
The intr option allows keyboard interrupts to kill a process
that is hung while waiting for a response on a hard-mounted
file system.
Quotas
Quota checking on NFS file systems is performed by the
server, not the client; if the file system has the quota
option on the server, quota checking is performed for both
local requests and NFS requests. When a user logs in,
login(1) runs the quota(1) program to check whether the user
is over their quota on any of the file systems mounted on
the machine. This check is performed for NFS file systems
by an RPC call to the rquotad(8C) server on the machine from
which the file system is mounted. This can be time-
consuming, especially if the remote machine is down. If the
noquota option is specified for an NFS file system, quota
will not check whether the user is over their quota on that
file system, which can speed up the process of logging in.
This does not disable quota checking for operations on that
file system; it merely disables reporting whether the user
is over quota on that file system.
Secure Filesystems
The secure option must be given if the server requires
secure mounting for the file system.
File Attributes
The attribute cache retains file attributes on the client.
Attributes for a file are assigned a time to be flushed. If
the file is modified before the flush time, then the flush
time is extended by the time since the last modification
(under the assumption that files that changed recently are
likely to change soon). There is a minimum and maximum
flush time extension for regular files and for directories.
Setting actimeo=n extends flush time by n seconds for both
regular files and directories.
SYSTEM V COMPATIBILITY
System V File-Creation Semantics
Ordinarily, when a file is created its GID is set to the
effective GID of the calling process. This behavior may be
overridden on a per-directory basis, by setting the set-GID
bit of the parent directory; in this case, the GID is set to
the GID of the parent directory (see open(2V) and
mkdir(2V)). Files created on file systems that are mounted
with the grpid option will obey BSD semantics; that is, the
GID is unconditionally inherited from that of the parent
directory.
EXAMPLES
To mount a local disk:
mount /dev/xy0g /usr
To fake an entry for nd root:
mount -ft 4.2 /dev/nd0 /
To mount all 4.2 file systems:
mount -at 4.2
To mount a remote file system:
mount -t nfs serv:/usr/src /usr/src
To mount a remote file system:
mount serv:/usr/src /usr/src
To hard mount a remote file system:
mount -o hard serv:/usr/src /usr/src
ground on failure:
To mount an RFS remote file system, retrying in the back-
mount -d -o bg SRC /usr/src
To mount an RFS remote file system read-only:
mount -t rfs -r SRC /usr/src
To save current mount state:
mount -p > /etc/fstab
Note: this is not recommended when running the
automounter, see automount(8).
To loopback mount file systems:
mount -t lo /export/tmp/localhost /tmp
mount -t lo /export/var/localhost /var lo
mount -t lo /export/cluster/sun386.sunos4.0.1 /usr/cluster
mount -t lo /export/local/sun386 /usr/local
FILES
/etc/mtab table of mounted file systems
/etc/fstab table of file systems mounted at boot
WARNINGS
mount does not understand the mount order dependencies
involved in loopback mounting. Loopback mounts may be
dependent on two mounts having been previously performed,
while nfs and 4.2 mounts are dependent only on a single pre-
vious mount. As a rule of thumb, place loopback mounts at
the end of the /etc/fstab file. See lofs(4S) for a complete
description.
SEE ALSO
mkdir(2V), mount(2V), open(2V), unmount(2V), lofs(4S),
fstab(5), mtab(5), automount(8), mountd(8C), nfsd(8)
BUGS
Mounting file systems full of garbage crashes the system.
If the directory on which a file system is to be mounted is
a symbolic link, the file system is mounted on the directory
to which the symbolic link refers, rather than being mounted
on top of the symbolic link itself.