[K12OSN] backup question

[Rob Owens]

--- Robert Arkiletian <robark at gmail.com> wrote:
> Are you sure? I wonder why I thought you could not
> cp the / filesystem
> unless you boot from another / system (ie live cd)?

rsync works differently than cp.  rsync is supposed to
take a "snapshot" of the files, and then copy them all
as they were at that instant in time.  (I'm sure it's
not an "instant", but it's apparently a very short
period of time).  cp on the other hand copies files
one by one, so if the files are changing while the
copying is being done, you may not end up with a
usable backup.  For instance, supppose some process
modifies files A and Z while you are doing cp.  When
cp started, you copied the old "A", but by the time cp
gets to copying "Z", you're copying the new "Z".

Everybody who is interested in backups should take a
look at this link: 
http://www.mikerubel.org/computers/rsync_snapshots/

It gives an excellent explanation of how a good backup
system works.  After reading it, I chose to run a
program called rsnapshot, which is linked off of this
page.  It works very well for me for home use.  I
think backuppc would probably be better for a network
evironment, because it can pool files from multiple
machines (according to Les' recent post).  But no
matter what, read that link.  It is great information.

-Rob



		
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