When UFS logging is enabled, UFS write operations are broken into transactions which are stored to a log before being committed to the filesystem. The use of UFS logging maintains filesystem consistency and prevents the need to run fsck against the filesystem. This can significantly reduce the time required to reboot a system.
UFS logging requires minimal system resources, using about 1 MB per GB of filesystem (although it can grow to no more than 64 MB/GB). UFS logging is disabled by default.
To enable UFS logging, alter the filesystem’s entry in /etc/vfstab to include the ‘logging’ option, such as the following:
/dev/dsk/c0t0d0s1 /dev/rdsk/c0t0d0s1 / ufs 1 yes logging
This will enable UFS logging on the root filesystem after the next system boot. To mount a filesystem from the command line with logging on, use the following mount command:
mount -F ufs -o logging /dev/dsk/c0t0d0s3 /mnt
To remount a currently mounted filesystem and enable logging, use the remount option as follows:
mount -F ufs -o remount,logging /var