System Administration Guide, Volume 1

Mounting File Systems

After you create a file system, you need to make it available to the system so you can use it. You make a file system available by mounting it, which attaches the file system to the system directory tree at the specified mount point. The root (/) file system is always mounted. Any other file system can be connected or disconnected from the root (/) file system.

The table below provides guidelines on mounting file systems based on how you use them.

Table 36-1 Determining How to Mount File Systems

If You Need to Mount ... 

Then You Should Use ... 

Local or remote file systems infrequently 

The mount command entered manually from the command line.

Local file systems frequently 

The /etc/vfstab file, which will mount the file system automatically when the system is booted in multi-user state.

Remote file systems frequently, such as home directories 

  • The /etc/vfstab file, which will automatically mount the file system when the system is booted in multi-user state.

  • AutoFS, which will automatically mount or unmount the file system when you change into (mount) or out of (unmount) the directory.

To enhance performance, you can also cache the remote file systems by using CacheFS. 

You can mount a CD-ROM containing a file system by simply inserting it into the drive (Volume Management will automatically mount it). You can mount a diskette containing a file system by inserting it into the drive and running the volcheck(1) command. See Chapter 14, Guidelines for Using CDs and Diskettes (Overview) for more information.

Commands Used to Mount and Unmount File Systems

The table below lists the commands in the /usr/sbin directory that you use to mount and unmount file systems.

Table 36-2 Commands for Mounting and Unmounting File Systems




Mounts file systems and remote resources. 


Mounts all file systems specified in the /etc/vfstab file. The mountall command is run automatically when entering multiuser run states.


Unmounts file systems and remote resources. 


Unmounts all file systems specified in the /etc/vfstab file.

The mount commands will not mount a read/write file system that has known inconsistencies. If you receive an error message from the mount or mountall command, you might need to check the file system. See Chapter 39, Checking File System Integrity for information on how to check the file system.

The umount commands will not unmount a file system that is busy. A file system is considered busy if a user is accessing a file or directory in the file system, if a program has a file open in that file system, or if the file system is shared.

Commonly Used Mount Options

The table below describes the commonly used mount options that you can specify with the -o option of the mount command. If you specify multiple options, separate them with commas (no spaces). For example, -o ro,nosuid.

For a complete list of mount options for each file system type, refer to the specific mount command man pages (for example, mount_ufs(1M)).

Table 36-3 Commonly Used -o Mount Options


File System 


bg | fg


If the first attempt fails, retries in the background (bg) or in the foreground (fg). This option is safe for non-critical vfstab entries. The default is fg.

hard | soft


Specifies the procedure if the server does not respond. soft indicates that an error is returned. hard indicates that the retry request is continued until the server responds. The default is hard.

intr | nointr


Specifies whether keyboard interrupts are delivered to a process that is hung while waiting for a response on a hard-mounted file system. The default is intr (interrupts allowed).

largefiles | nolargefiles


Enables you to create files larger than 2 Gbytes. The largefiles option means that a file system mounted with this option might contain files larger than 2 Gbytes, but it is not a requirement. The default is largefiles. If the nolargefiles option is specified, the file system could not be mounted on a system running Solaris 2.6 or compatible versions.

logging | nologging


Enables logging for the file system. UFS logging is the process of storing transactions (changes that make up a complete UFS operation) into a log before the transactions are applied to the UFS file system. Logging helps prevent UFS file systems from becoming inconsistent, which means fsck can be bypassed. Bypassing fsck reduces the time to reboot a system if it crashes, or after a system is shutdown uncleanly.

The log is allocated from free blocks on the file system, and is sized approximately 1 Mbyte per 1 Gbyte of file system, up to a maximum of 64 Mbytes. The default is nologging.



Suppresses 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). The default is normal access time (atime) recording.



Changes the mount options associated with an already-mounted file system. This option can generally be used with any option except ro, but what can be changed with this option is dependent on the file system type.



Retries the mount operation when it fails. n is the number of times to retry.

ro | rw


Specifies read/write or read-only. If you do not specify this option, the default is read/write. The default option for HSFS is ro.

suid | nosuid


Allows or disallows setuid execution. The default is to allow setuid execution.

How to Determine Which File Systems Are Mounted

You can determine which file systems are mounted by using the mount command.

$ mount [ -v ]


Displays the list of mounted file systems in verbose mode. 

Example--Determining Which File Systems Are Mounted

$ mount
/ on /dev/dsk/c0t0d0s0 read/write/setuid/intr/largefiles/onerror=panic on ...
/usr on /dev/dsk/c0t0d0s6 read/write/setuid/intr/largefiles/onerror=panic on ...
/proc on /proc read/write/setuid on Fri Sep 10 16:09:48 1999
/dev/fd on fd read/write/setuid on Fri Sep 10 16:09:51 1999
/etc/mnttab on mnttab read/write/setuid on Fri Sep 10 16:10:06 1999
/var/run on swap read/write/setuid on Fri Sep 10 16:10:06 1999
/tmp on swap read/write/setuid on Fri Sep 10 16:10:09 1999
/export/home on /dev/dsk/c0t0d0s7 read/write/setuid/intr/largefiles/onerror=panic ...