System Administration Guide, Volume 1

Modifying File System Checking at Boot Time

During boot up, a preliminary check on each file system to be mounted from a hard disk is run using the boot script /sbin/rcS, which checks the root (/), /usr, and /var file systems. The other rc shell scripts then use the fsck command to check each additional file system sequentially. They do not check file systems in parallel. File systems are checked sequentially during booting even if the fsck pass numbers are greater than one.

The /etc/vfstab File

When you run the commands for checking and mounting file systems without specifying a file system directly, the commands step through the file system table (/etc/vfstab) using the information specified in the various fields. The fsck pass field specifies information for file system checking. The mount at boot field specifies information for mounting the file system at boot time.

When you create new file systems, add entries to /etc/vfstab indicating whether they are to be checked and mounted at boot time. See Chapter 36, Mounting and Unmounting File Systems (Tasks) for more information about adding entries to the /etc/vfstab file.

Information in the /etc/vfstab file is specific for the slices and file systems for each system. Here is an example of an /etc/vfstab file:

$ more /etc/vfstab
#device         device          mount           FS      fsck    mount    mount
#to mount       to fsck         point           type    pass    at boot  options
#/dev/dsk/c1d0s2 /dev/rdsk/c1d0s2 /usr          ufs     1       yes     -
/proc           -               /proc           proc    -       no      -
fd              -               /dev/fd         fd      -       no      -
swap            -               /tmp            tmpfs   -       yes     -
/dev/dsk/c0t0d0s0 /dev/rdsk/c0t0d0s0 /          ufs     1       no      -
/dev/dsk/c0t0d0s1 -                  -          swap    -       no      -
/dev/dsk/c0t0d0s6 /dev/rdsk/c0t0d0s6 /usr       ufs     2       no      -
/dev/dsk/c0t0d0s7 /dev/rdsk/c0t0d0s7 /opt       ufs     3       yes     -
pluto:/usr/dist	-    				/usr/dist       nfs     no      yes     -

The table below describes the function of the fsck pass field.

Table 39-3 The fsck pass Field

If the fsck pass Field is Set To ...

Then ... 


- (hyphen)

The generic fsck command will not check the file system regardless of the state of the file system.

Use a hyphen for read-only file systems, remote file systems, or pseudo file systems, such as /proc, to which checking does not apply.


The file system specific fsck command is called.

When the value is 0 for UFS file systems, the file system is not checked.

1 or greater and fsck -o p is used

The file system specific fsck automatically checks UFS file systems in parallel.

The value can be any number greater than 1.  

In preen mode (-o p option), fsck allows only one active file system check per disk, starting a new check only after the previous one is completed. fsck automatically uses the major and minor numbers of the devices on which the file systems reside to determine how to check file systems on different disks at the same time.

When the fsck pass number is 1, file systems are checked sequentially, in the order they appear in the /etc/vfstab file. Usually, the root (/) file system has the fsck pass set to 1.

Note -

fsck does not use the fsck pass number to determine the sequence of file system checking.

How to Modify File System Checking at Boot Time

  1. Become superuser.

  2. Edit /etc/vfstab entries in the fsck pass field, and save the changes.

    The next time the system is booted, the new values are used.