I'm working on a backup script (backups to NAS) and was looking for some
clarification on tar command options.

I would like to do a complete tar archive once a week, with incremental
on all other days.

Common Variables are:
DATE=$(/bin/date -I)
NAME=$(/bin/uname -n)
DEST=/mnt/backup
FILENAME=$NAME.$DATE.tar

The complete backup tar command is:
tar -Pcvpf $DEST/$FILENAME -X /etc/backup.exclude --verify /

The incremental backup tar command (and the one I have questions on):
tar -Pcpvf $DEST/$FILENAME -X /etc/backup.exclude --verify
--newer=/etc/backup.DATE /

Questions:
It's not clear to me what exactly DATE should be when using the --newer
(-N, --after-date) options.
The man page only shows;
-N, --after-date DATE, --newer DATE
              only store files newer than DATE

Is this supposed to a time stamp of some sort, like DEC 12, 2004? What
is the format?  
Can it be a file, so incremental backups all files newer than DATE of
file (as I have attempted to use)?
For example, which is the proper use?
--newer with some kind of Date specified;
tar -Pcvpf $DEST/$FILENAME -X /etc/backup.exclude --verify --newer=DEC
9, 2004

--newer with file name specified (in the hope incremental grabs anything
newer than timestamp on file)
tar -Pcvpf $DEST/$FILENAME -x /etc/backup.exclude --verify
--newer=/etc/backup.DATE

NOTE:
/etc/backup.DATE is modified after each backup script run by echoing
$DATE
DATE=$(/bin/date -I)
...
Backup script
...
echo $DATE > /etc/backup.DATE


Any other suggestions on better ways to do handle full/incremental
backups?

______________________________
James

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