backup advice

[James R. Van Zandt]

Bryan -

You write:
>I'd like everyone's advice on how to backup the following system layout on
>my home LAN:
>
>
>Systems:    1 linux box w/ 7.0 GB HD (1.2 used currently)
>            1 linux box w/ 5.8 GB HD (2.5 used currently)
>            1 sparc box w/ 1.4 GB HD (nearly full)
>
>I want to back up critical files, user homes, mail, etc. on a regular
>basis and have figured out a backup schedule (incremental) to do this..
>what would be the best method?  
>
>I was contemplating backing up using tar over nfs to one of the machines,
>then circulating that copy to the other linux box...  any other ideas?

I suggest tar over rsh.  A trick is needed to run the tar command as
root (so it has read access to any file), but the rsh as a normal user
(so it can login to the other machine).  I believe I first saw this in
the docs to "tob".  The trick is to connect the two processes with a
named pipe (created with "mkfifo /mypipe").  I use something like
this:

  su jrv -c "rsh $HOST \"cat >/usr1/backup/home.tar.gz\" < /mypipe"&
  cd /
  tar -czf - home >/mypipe

Here, this command gets run as normal user `jrv', taking its input
from the named pipe on this machine:

  rsh $HOST "cat >/usr1/backup/home.tar.gz" < /mypipe

This command gets run on the other machine ($HOST):

  cat >/usr1/backup/home.tar.gz

This command, of course, makes and compresses the backup and writes it
to the named pipe:

  tar -czf - home >/mypipe

I suppose cpio can work the same way, but I am more comfortable with tar.

With your setup, I guess I would back machine 1->2, 2->1, and 3->1.

Advantages:
 - Only needs ordinary user privileges on the other machine.
 - Faster than NFS.
 - The userids and groupids on the two machines need not match (unlike
NFS). 
 - If you back up to a disk, you can fully automate things with a cron
job.


Disadvantages:
 - Slower and more awkward to search through than NFS (to recover a 
single file)
 - Not secure (though switching from rsh to ssh would help).

		- Jim Van Zandt
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