Michael Tokarev writes:
: Dean S. Messing wrote:
: > Michal Soltys writes:
: []
: > : Rsync is fantastic tool for incremental backups. Everything that didn't
: > : change can be hardlinked to previous entry. And time of performing the
: > : backup is pretty much neglible. Essentially - you have equivalent of
: > : full backups at almost minimal time and space cost possible.
: >
: > It has been some time since I read the rsync man page. I see that
: > there is (among the bazillion and one switches) a "--link-dest=DIR"
: > switch which I suppose does what you describe. I'll have to
: > experiment with this and think things through. Thanks, Michal.
:
: I haven't actually read the rsync manpage to this detail, but I
: do use rsync for backups this way, but a bit differently - yet
: more understandable without referring to manpages... ;)
:
: the procedure is something like this:
:
: cd /backups
: rm -rf tmp/
: cp -al $yesterday tmp/
: rsync -r --delete -t ... /filesystem tmp
: mv tmp $today
:
: That is, link the previous backup to temp (which takes no space
: except directories), rsync current files to there (rsync will
: break links for changed files), and rename temp to $today.
Very nice. The breaking of the hardlink is the key. I wondered about
this when Michal using rsync yesterday. I just tested the idea. It
does indeed work.
One question: why do you not use "-a" instead of "-r -t"? It would
seem that one would want to preserve permissions, and group and user
ownerships. Also, is there a reason to _not_ preserve sym-links
in the backup. Your script appears to copy the referent.
Dean
P.S. I think this thread has wandered from the topic of "linux-raid".
I'm happy to cease and desist if this Off Topic discussion
offends.
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