Re: about usage scenarios

[Daniel Staal <DStaal@usa.net>]

--As of June 27, 2011 1:51:08 PM -0500, Harry Putnam is alleged to have 
said:

> -------        ---------       ---=---       ---------      --------
> In summary: I'd setup a sshfs mnts on the host running tarsnap, for
> each machine where I had something to backup. Then mount all the
> necessary machines and run thru them using tarsnap to put the stuff on
> whatever tarsnap puts them on.
> -------        ---------       ---=---       ---------      --------

Sounds decent.  I run something slightly similar: I have a central server 
that shares directories via NFS, and they are backed up.  Which is inverted 
from your situation (from my understanding, you store the data on all the 
machines, then have it backed up from a machine that mounts shares from 
them), but should be fine.

Note that your way will put quite a bit of load on your home network during 
backups.  Though as long as your upstream connection to the internet is 
substantially slower than your local net (like most are), that shouldn't be 
a problem.

You could run tarsnap on each box if you wanted, but then you'd be 
de-centralizing your scheduling.  (And allowing yourself to try to run two 
backups at once, which won't be any faster overall than running them 
sequentially.)

Whichever way you go there, you have two basic approaches you can use: You 
can create a separate key for each box, or you can use the same key for all 
your boxes and use the names of the archives to know which is for which box.

If you have a central backup box, the separate key becomes a bit more 
complicated, but not extremely so.  (You'd need to set the --keyfile  and 
--cachedir options correctly for each run, or have a separate config file 
for each machine-set that you specify on each run with --configfile that 
has them.)

Simple backup command line:  (Assuming you are using one key file for all 
boxes, and it's already been created, and that you either have a config 
file in the standard place or are accepting all defaults.  This is the 
backups for 'machine-alpha'.)
tarsnap -cf machine-alpha-`date +\%F` /path/to/machine-alpha/dir

That can be run once daily, and it would create an archive for each day 
with the date appended.

> I guess the resulting backups work something like rsnapshot? If so
> then is finding copies of stuff somewhat involved like it is with
> rsnapshot?

Not really.  It's like tar. ;)  You can restore specific files out of a 
backup by name, but you'll either need to get a file listing first, or know 
the name of the file you want.  There's a couple of different ways to let 
it know which files you want (shell patterns or read from a file).  I 
haven't tried it, but I suspect from the way that tarsnap works that it 
will have to do it somewhat like tar would: that it will have to read more 
of the archive than just the file it needs.  (How much more I don't know. 
Probably not quite as much as tar would...)

Daniel T. Staal

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