NAME

mount - mount remote NFS resources

SYNOPSIS

mount [ -F nfs ] [ -r ] [ -o specific_options ]  [  resource
mountpoint ]

DESCRIPTION

The mount command attaches a named resource to the file system hierarchy at the pathname location mountpoint, which must already exist. If mountpoint has any contents prior to the mount operation, the contents remain hidden until the resource is once again unmounted.

If the resource is listed in the vfstab file, the command line can specify either resource or mountpoint, and mount will consult vfstab for more information. If the -F option is omitted, mount will take the file system type from vfstab.

mount maintains a table of mounted file systems in /etc/mnttab, described in mnttab(4).

The following options are available to the mount command:

-r   Mount the specified file system read-only.

-o specific_options

Specify file system specific options in a comma-separated list of words from the list below.

rw|ro         resource is mounted read-write  or  read-
              only.  The default is rw.
suid|nosuid   Setuid execution allowed  or  disallowed.
              The default is suid.
remount       If a file system  is  mounted  read-only,
              remounts the file system read-write.
bg|fg         If the first attempt fails, retry in  the
              background,  or,  in the foreground.  The
              default is fg.
retry=n       The number of times to  retry  the  mount
              operation.  The default is 10000.
port=n        The server IP port number.   The  default
              is NFS_PORT.
grpid         Create a file with its  GID  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(2)   and
              mkdir(2)].  Files created on file systems
              that  are  not  mounted  with  the  grpid
              option  will obey BSD semantics; that is,
              the GID is unconditionally inherited from
              that of the parent directory.
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     Set the number of NFS retransmissions  to
              n.
soft|hard     Return an error if the  server  does  not
              respond,  or  continue  the retry request
              until the server responds.
intr          Allow keyboard interrupts to kill a  pro-
              cess  that  is  hung  while waiting for a
              response on a hard-mounted file system.
secure        Use a more secure protocol for NFS  tran-
              sactions.
noac          Suppress attribute caching.
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 modification.
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.

NFS FILE SYSTEMS

Background vs. Foreground

File systems mounted with the bg option indicate that mount is to retry in the background if the server's mount daemon [mountd(1M)] 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.

Secure File Systems

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.

EXAMPLES

To mount a remote file system: mount  -F  nfs  serv:/usr/src
/usr/src
To  hard  mount  a  remote  file  system:  mount   -o   hard
serv:/usr/src /usr/src

FILES

/etc/mnttab         table of mounted file systems
/etc/dfs/fstypes    default distributed file system type
/etc/vfstab         table of automatically mounted resources

SEE ALSO

mountall(1M), mount(2), umount(2), mnttab(4).

NOTES

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.