Re: rescue bootable cd ???
On 10/01/07 05:15:27PM -0500, C M Reinehr wrote:
> I've seen the term before but don't understand exactly what COW means, but I
> think I know what you're talking about. I had a failing disk drive last
> Friday and had to boot my system off of a Knoppix disk to see what I could
> salvage from my raid-1 array. Knoppix didn't seem to include the
> smartmontools package but I was able to use apt-get to install it on the fly
> and use it to diagnose which disk was failing.
COW stands for copy on write, whenever a change is made to a block (or
file maybe, I don't know what granularity unionfs uses) that block is
copied somewhere else and the original left in place so that the update
can succeed and the original still exists. Sort of like an LVM snapshot only
instead of being backed by a LVM volume the changes are only stored in memory.
But yea, the short answer is that it allows you to make changes and install
software on read-only medium like CDs. =)