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:

When logging is specifically disabled.
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 nodfratime.

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 file.

June 22, 2009 OmniOS