System Administration Guide, Volume I

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.

Table 28-1 provides guidelines on mounting file systems based on how you use them.

Table 28-1 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 11, Guidelines for Using CDs and Diskettes (Overview) for more information.

Commands Used to Mount and Unmount File Systems

Table 28-2 lists the commands in the /usr/sbin directory that you use to mount and unmount file systems.

Table 28-2 Commands for Mounting and Unmounting File Systems


Command	Description
mount(1M)	Mounts file systems and remote resources.
mountall(1M)	Mounts all file systems specified in the `/etc/vfstab` file. The `mountall` command is run automatically when entering multiuser run states.
umount(1M)	Unmounts file systems and remote resources.
umountall(1M)	Unmounts all file systems specified in the `/etc/vfstab` file.

The mount commands will not mount a read/write file system that has inconsistencies. If you receive an error message from the mount or mountall command, you may need to check the file system. See Chapter 31, 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 in a directory in the file system, or if a program has a file open in that file system.

Commonly Used Mount Options

Table 28-3 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 28-3 Commonly Used -o Mount Options


Option	File System	Description
`bg \| fg`	NFS	If the first attempt fails, retries in the background (`bg`) or in the foreground (`fg`). The default is `fg`.
`f`	UFS	Fakes an entry in `/etc/mnttab`, but doesn't really mount any file systems.
`hard \| soft`	NFS	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`	NFS	Specifies whether keyboard interrupts are allowed to kill a process hung while waiting for a response on hard-mounted file systems. The default is `intr` (interrupts allowed).
`largefiles \| nolargefiles`	UFS	Enables you to create file systems containing files larger than 2 Gbytes. The `largefiles` option means that a filesystem mounted with this option may contain files larger than 2 Gbytes, but it is not a requirement. The default is `largefiles`.
`logging \| nologging`	UFS	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. Because the file system can never become inconsistent, `fsck` can be bypassed, which reduces the time to reboot a system if it crashes, or after an unclean halt. 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`.
`m`	CacheFS, NFS, PCFS, S5FS, UFS	Mounts the file system without making an entry in `/etc/mnttab`.
`noatime`	UFS	Ignores 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.
`remount`	NFS, S5FS, UFS	Remounts a read-only file system as read-write (using the `rw` option). This option can be used only in conjunction with the `f`, `logging \| nologging`, and `m` options. This option works only on currently mounted read-only file systems.
`retry=n`	NFS	Retries the mount operation when it fails. `n` is the number of times to retry.
`ro \| rw`	CacheFS, NFS, PCFS, UFS, S5FS	Specifies read/write or read-only. If you do not specify this option, the default is read/write.
`suid \| nosuid`	CacheFS, HSFS, NFS, S5FS, UFS	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

`-v`	Displays the list of mounted file systems in verbose mode.

Example--Determining Which File Systems Are Mounted

$ mount
/ on /dev/dsk/c0t3d0s0 read/write/setuid/largefiles on ...
/usr on /dev/dsk/c0t3d0s6 read/write/setuid/largefiles on ...
/proc on /proc read/write/setuid on Mon Jun 8 10:28:31 1998
/dev/fd on fd read/write/setuid on Mon Jun 8 10:28:31 1998
/export on /dev/dsk/c0t3d0s3 setuid/read/write/largefiles on ...
/export/home on /dev/dsk/c0t3d0s7 setuid/read/write/largefiles on ...
/export/swap on /dev/dsk/c0t3d0s4 setuid/read/write/largefiles on ...
/opt on /dev/dsk/c0t3d0s5 setuid/read/write/largefiles on ...
/tmp on swap read/write on Mon Jun 8 10:28:31 1998
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