MOUNT_UFS(8) Maintenance Commands and Procedures MOUNT_UFS(8)


mount_ufs - mount ufs file systems


mount -F ufs [generic_options] [-o specific_options]
[-O] special | mount_point

mount -F ufs [generic_options] [-o specific_options]
[-O] special mount_point


The mount utility attaches a ufs file system to the file system hierarchy
at the mount_point, which is the pathname of a directory. If mount_point
has any contents prior to the mount operation, these are hidden until the
file system is unmounted.

The ufs file system supports direct mounting of files containing the file
system as well as block devices. See mount(8) and lofiadm(8).

If mount is invoked with special or mount_point as the only arguments,
mount will search /etc/vfstab to fill in the missing arguments, including
the specific_options. See mount(8).

If special and mount_point are specified without any specific_options,
the default is rw.

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 on top of the symbolic link itself.


See mount(8) for the list of supported generic_options.

The following options are supported:

-o specific_options

Specify ufs file system specific options in a comma-separated list
with no intervening spaces. If invalid options are specified, a
warning message is printed and the invalid options are ignored. The
following options are available:

dfratime | nodfratime

By default, writing access time updates to the disk may be
deferred (dfratime) for the file system until the disk is
accessed for a reason other than updating access times.
nodfratime disables this behavior.

If power management is enabled on the system, do not set
nodfratime unless noatime is also set. If you set nodfratime
without setting noatime, the disk is spun up every time a file
within a file system on the disk is accessed - even if the file
is not modified.

forcedirectio | noforcedirectio

If forcedirectio is specified and supported by the file system,
then for the duration of the mount, forced direct I/O will be
used. If the filesystem is mounted using forcedirectio, data is
transferred directly between user address space and the disk. If
the filesystem is mounted using noforcedirectio, data is buffered
in kernel address space when data is transferred between user
address space and the disk. forcedirectio is a performance option
that is of benefit only in large sequential data transfers. The
default behavior is noforcedirectio.

global | noglobal

If global is specified and supported on the file system, and the
system in question is part of a cluster, the file system will be
globally visible on all nodes of the cluster. If noglobal is
specified, the mount will not be globally visible. The default
behavior is noglobal.

intr | nointr

Allow (do not allow) keyboard interrupts to kill a process that
is waiting for an operation on a locked file system. The default
is intr.

largefiles | nolargefiles

If nolargefiles is specified and supported by the file system,
then for the duration of the mount it is guaranteed that all
regular files in the file system have a size that will fit in the
smallest object of type off_t supported by the system performing
the mount. The mount will fail if there are any files in the file
system not meeting this criterion. If largefiles is specified,
there is no such guarantee. The default behavior is largefiles.

If nolargefiles is specified, mount will fail for ufs if the file
system to be mounted has contained a large file (a file whose
size is greater than or equal to 2 Gbyte) since the last
invocation of fsck on the file system. The large file need not be
present in the file system at the time of the mount for the mount
to fail; it could have been created previously and destroyed.
Invoking fsck (see fsck_ufs(8)) on the file system will reset the
file system state if no large files are present. After invoking
fsck, a successful mount of the file system with nolargefiles
specified indicates the absence of large files in the file
system; an unsuccessful mount attempt indicates the presence of
at least one large file.

logging | nologging

If logging is specified, then logging is enabled for the duration
of the mounted file system. Logging is the process of storing
transactions (changes that make up a complete UFS operation) in a
log before the transactions are applied to the file system. Once
a transaction is stored, the transaction can be applied to the
file system later. This prevents file systems from becoming
inconsistent, therefore reducing the possibility that fsck might
run. And, if fsck is bypassed, logging generally reduces the
time required to reboot a system.

The default behavior is logging for all UFS file systems.

The log is allocated from free blocks in the file system, and is
sized approximately 1 Mbyte per 1 Gbyte of file system, up to a
maximum of 256 Mbytes. The log size may be larger (up to a
maximum of 512 Mbytes) dependent upon the number of cylinder
groups present in the file system.

Logging is enabled on any UFS file system, including root (/),
except under the following conditions:

o When logging is specifically disabled.

o If there is insufficient file system space for the
log. In this case, the following message is displayed
and file system is still mounted:

# mount /dev/dsk/c0t4d0s0 /mnt
/mnt: No space left on device
Could not enable logging for /mnt on /dev/dsk/c0t4d0s0.

The log created by UFS logging is continually flushed as it fills
up. The log is totally flushed when the file system is unmounted
or as a result of the lockfs -f command.


Mount the file system without making an entry in /etc/mnttab.


By default, the file system is mounted with normal access time
(atime) recording. If noatime is specified, the file system will
ignore access time updates on files, except when they coincide
with updates to the ctime or mtime. See stat(2). This option
reduces disk activity on file systems where access times are
unimportant (for example, a Usenet news spool).

noatime turns off access time recording regardless of dfratime or

The POSIX standard requires that access times be marked on files.
-noatime ignores them unless the file is also modified.


By default, Access Control Lists (ACLs) are supported on a
mounted UFS file system. Use this option to disallow the setting
or any modification of an ACL on a file within a mounted UFS file
system. See getfacl(1) for background on ACLs.

onerror = action

This option specifies the action that UFS should take to recover
from an internal inconsistency on a file system. Specify action
as panic, lock, or umount. These values cause a forced system
shutdown, a file system lock to be applied to the file system, or
the file system to be forcibly unmounted, respectively. The
default is panic.


Quotas are turned on for the file system.


Remounts a file system with a new set of options. All options not
explicitly set with remount revert to their default values.


Read-write with quotas turned on. Equivalent to rw, quota.

xattr | noxattr

Allow or disallow the creation and manipulation of extended
attributes. The default is xattr. See fsattr(7) for a description of
extended attributes.


Overlay mount. Allow the file system to be mounted over an existing
mount point, making the underlying file system inaccessible. If a
mount is attempted on a pre-existing mount point without setting this
flag, the mount will fail, producing the error "device busy".


Example 1: Turning Off (and On) Logging

The following command turns off logging on an already mounted file
system. The subsequent command restores logging.

# mount -F ufs -o remount,nologging /export
# (absence of message indicates success)
# mount -F ufs -o remount,logging /export

In the preceding commands, the -F ufs option is not necessary.



table of mounted file systems


list of default parameters for each file system


getfacl(1), fcntl(2), mount(2), stat(2), mnttab(5), vfstab(5),
attributes(7), fsattr(7), largefile(7), fsck(8), fsck_ufs(8), lofiadm(8),
mount(8), mountall(8)


Since the root (/) file system is mounted read-only by the kernel during
the boot process, only the remount option (and options that can be used
in conjunction with remount) affect the root (/) entry in the /etc/vfstab

illumos June 22, 2009 MOUNT_UFS(8)