[K12OSN] Re: Re: Got to rebulid -- how to take an image for checkpointing (Chuck Kollars)

[Matt Oquist]

> Date: Sat, 26 Aug 2006 21:14:55 -0700 (PDT)
> From: Chuck Kollars <ckollars9 at yahoo.com>
> Subject: Re: [K12OSN] Got to rebulid -- how to take an image for checkpointing

> doesn't just affect Windows.  In Linux files whose
> name starts with a "." are conventionally not
> displayed.  Ever done a `cp` only to discover none
> of the "dot" files were copied?

Nobody's recommended 'cp' yet as an adequate OS backup tool. :)

> 2) Several OSs have alternate portions of files
> that aren't normally visible.  Mac's have the
> "resource fork"; Windows has "streams".  These are
> visible through standard (if little-used) system
> calls; there's no reason a really good backup
> program couldn't handle them correctly.

Do the backup programs available for Windows and Mac handle them
correctly? I presume so.

> 3) In most modern OSs there can be "metadata"
> associated with each file.  Even Linux has this
> option, which unfortunately most of its programs
> don't handle  correctly.  Have you ever backed up
> a file system that uses ACLs (Access Control
> Lists) with `tar`, restored it elsewhere, and
> wondered what happened to all your ACLs?

This is a good point - yet ACLs are used (regrettably) uncommonly, so
the vast majority of admins won't run into this. (And at this point,
if they're using ACLs, they're beyond discussing system backups at
this level.)

> 4) Some applications (think "AD") are paranoid
> about security but don't support adequate recovery
> procedures.  Consider an application that changes
> its hashes every fifteen minutes, embeds
> timestamps in its data, and doesn't provide a way
> to resynchronize.  It's almost impossible to back
> up, not only as a collection of files but even as
> a collection of raw sectors (which is how 
> "ghosting" tools would see it).

Right; and this is why regular backups should be performed not just at
a system level, but of each important database in a way that allows
for straightforward recovery.

> So yes doing a naive file-by-file copy often 
> doesn't do what you want it to, especially with
> Windows. But no there's no need to postulate
> secret binary data to explain why.

No *need*, but it sure is *fun*. :-)

But seriously, a file-by-file backup and restore of Windows just plain
isn't possible (AFAIK), and that's the difference I was pointing out.
*Most* Linux systems at this point can be backed up and restored via
'tar' or 'rsync' (or 'cpio', or even 'cp' with the right options).

--matt

--
Open Source Software Engineering Consultant
http://majen.net/
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