[lug] /etc backup and unionfs(?)

Bear Giles bgiles at coyotesong.com
Fri Jun 8 14:56:34 MDT 2007

Michael J. Hammel wrote:
> On Fri, 2007-06-08 at 09:04 -0600, Bear Giles wrote:
>> Live CDs are now able to run off a root image on the cd media.  It looks 
>> like there's a unionfs that allows a ramdisk to overlay the read-only disk.
>> That made me think -- what if the hard disk's / image is solely what's 
>> in the distribution packages and is read-only, and you overlay it with a 
>> read-write partition?  Wouldn't that mean that all configuration changes 
>> are in that overlay partition and easily backed up and restored?  It 
>> would also be easy to check for unwanted modifications, e.g., attempts 
>> to install compromised binaries.
> Not sure I'm following this.  You're overlaying the root partition,
> which is mounted read-only, with a read-write partition so that you can
> easily do backups of the overlay?  I'm not clear on what that's buying
> you.
Overlaying the root partition, which contains unmodified distro 
packages, with an overlay that holds the actual configuration and 
customization for the system.

That means you don't have to back up the root partition.  In fact you 
shouldn't -- if the system is compromised you'll want to reinstall from 
"original media" anyway.  Everything you need to back up will be in the 
overlay partition, or the usual separate partitions such as /home.  
These backups will be small -- you might even to automatically mail them 
to yourself as a fairly small tarball.

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