HP-UX System Administrator's Guide: Routine Management Tasks

This brings up the question, “how does fbackup know when the previous backup
was created?” This information is contained in the file
/var/adm/fbackupfiles/dates, a file that is updated only when all of the following
conditions are true:
• The -u option is used with fbackup.
• A graph file is used to indicate which files should be included/excluded when a
backup is performed.
• Neither the -i nor the -e option is used (graph file used instead)
• The backup completed successfully
Backup levels are a way of specifying varying degrees of incremental backup. For
example, suppose you wanted to set up the following backup schedule:
• On the first day of the month, back up an entire set of selected files (a monthly,
full backup).
• Every Friday, back up all files in the selected set that have changed since the
previous Friday (a weekly, incremental backup so that you can back up and restore
files that have been active within the month, relatively quickly).
• Every day except Friday (or the first of the month), back up all of the files in the
selected set that have changed since the previous day (a daily, incremental backup,
so that you can quickly back up and restore files that have been active within the
last week).
There are three “layers” (levels) associated with the above schedule (the once per month
level, the once per week level, and the once per day level). The once per month level
is a full backup. The other two are incremental backups. The problem is how to
distinguish between the two types of incremental backup. This is accomplished with
backup levels.
The file /var/adm/fbackupfiles/dates contains information about when the last
backup at each backup level was performed. This information is used by fbackup,
along with the modification date stamps on the files themselves, to determine which
files in the specified set are to be included with the backup that is currently being
created.
As previously stated, you can have up to 10 backup levels. When you run fbackup,
you can tell it which level to use. fbackup will use the level you give it as follows:
• Level 0 is always considered a full backup
• Higher levels are generally used to perform incremental backups.
• When doing an incremental backup of a particular graph (specified by a graph
file name), at a particular level, fbackup will search the file
/var/adm/fbackupfiles/dates to find the date of the most recent backup of
the same graph that was done at a lower level. If no such entry is found, the
beginning of time is assumed. All files in the specified graph that have been
modified since this date are backed up
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