The ufsdump command, when used with the -u option, maintains and updates the /etc/dumpdates file. Each line in /etc/dumpdates shows the file system backed up, the level of the last backup, and the day, date, and time of the backup. Here is a typical /etc/dumpdates file from a file server:
/dev/rdsk/c0t0d0s0 9 Tue Jul 13 10:58:12 1999 /dev/rdsk/c0t0d0s0 0 Tue Jul 13 10:46:09 1999 /dev/rdsk/c0t0d0s1 0 Tue Jul 13 13:41:04 1999
When you do an incremental backup, the ufsdump command consults /etc/dumpdates to find the date of the most recent backup of the next lower level. Then it copies to the media all files that were modified since the date of that lower-level backup. After the backup is complete, a new information line, describing the backup you just completed, replaces the information line for the previous backup at that level.
Use the /etc/dumpdates file to verify that backups are being done. This verification is particularly important if you are having equipment problems. If a backup cannot be completed because of equipment failure, the backup is not recorded in the /etc/dumpdates file.
If you need to restore an entire disk, check the /etc/dumpdates file for a list of the most recent dates and levels of backups so that you can determine which tapes you need in order to restore the entire file system.
The /etc/dumpdates file is a text file that can be edited, but edit it only at your own risk. If you make changes to the file that do not match your archive tapes, you might not be able to find the tapes (or files) you need.