Re: backup compress on the fly
Joe Mc Cool wrote:
Please,
my ancient, but reliable, backup script is essentially:
find /my_dir | cpio -ov > /dev/st0
But, (now that I have installed all those lovely debian goodies), the
wretched tape is filling up and asking for another. (I erase the
tape beforehand.)
I really want to fit all my current data, or certainly selected dirs
unto one tape. Surely I should be able to compress the files before
they are sent to the tape. I suspect it can be done with gzip, but I am not
sure of the syntax. Obviously I need to get it right.
Whether compression is advisable depends on what your goal is.
If you are making archives, or you are backing up a system which,
if it failed and you lost everything it would be a terrible
disaster, then I recommend you *not* to compress your backups.
Compressed file formats are notoriously intolerant of medium
errors. It might be better to do subset backups each of which
fits onto a single tape.
Proceeding on,
There are three (at least) ways to proceed.
Abandon cpio and use a tar which can compress/decompress as it goes.
Continue to use cpio, and compress the image it creates.
Continue to use cpio, and compress the files before they are stored.
I am more familiar with tar than cpio. With the current GNU tar
releases, this would be
# tar cvz [list of places to back up]
The "c" means "create", the "v" is "verbose" (optional) and the "z"
means "compress as with gzip the entire tar image".
To test the backup, use
# tar tvz
To restore
# tar xvz [list of places to restore]
(Again, the "v" is optional.)
See the man page or info for more. If you have a favorite
compression program, you can even use that, if you like.
Mike
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