tar --listed-incremental
Hi,
I'm trying to use tar for incremental backups. After reading what I could
find on the web, it looks as if I need to use the "--listed-incremental"
option. With this option tar creates a file that keeps track of the changes.
So if (in /home/ric) I type:
tar -cvf /mnt/BACKUP1 --listed-incremental=LIST /home/ric/
to begin my backup, tar will create a file "LIST" in my home directory which
keeps track of what is archived on whatever I have mounted at /mnt. I can
then do incremental backups by simply modifying the name of the file:
tar -cvf /mnt/BACKUP2 --listed-incremental=LIST /home/ric/
and the file LIST is modified in my home directory.
To restore my home directory I would go to /home/ric and type:
tar -xvf /mnt/BACKUP1
this creates a home/ric/copy of my original archive. For each incremental
backup, I then type:
tar -xvf /mnt/BACKUP1 --listed-incremental=LIST
which seems to restore my home directory to the state it was in at the
last incremental backup.
What puzzles me is that the file LIST is restored when I do the first
restore from the first tar archive. The listed-incremental option looks at
this list when it restores the first incremental update (which has the
version of LIST used for that archive). The listed-incremental option looks
at the 2nd version of LIST when it restores the 3d incremental archive (which
contains the version of LIST that was used to create that archive). So it
initially looks as if tar is always one step behind in using the correct file
LIST. However, when I try this experimentally, things seem to work out fine.
I suppose ideally that I should keep a copy of LIST somewhere independent of
the directory being backed up, but then I have to worry about keeping it and
the tar archives.
I hope this confusion or puzzlement of mine makes sense. I'd appreciate any
suggestions on how to use the --listed-incremental option, or comments about
this use of it. It doesn't look to me as if it should work, but it seems to
do fine.
Thanks,
Ric
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