[SLUG] LPI 1.102.1 design hard disc layout

[Jonathan Worthington]

"Stephen O'Neill" <soneill84 at yahoo.co.uk> wrote:
> following that train of thought do you happen to know if there are 
> utilities for manipulating the journal? E.g. is it something that you 
> could initiate a restore to a point in time from?
>
The journal doesn't go back very far - it only need maintain a list of 
things that are currently happening to the file system to do its job, which 
is recovery after a crash.  And usually you only journal file metadata, not 
file content.  There's a good article here:-
http://www.linux-mag.com/2002-10/jfs_01.html

The idea of being able to restore an entire file system complete with data 
to a particular point in time has had some research though - I believe file 
systems that do this are commonly known as immutable file systems.  It'd 
basically be like implementing revision control, but at a file system level. 
I guess it'd have its uses, but you likely wouldn't want it on every file. 
When people care about revision control they usually use something like CVS 
or SVN and maintain it in user space.  Note that some Linux file systems do 
allow a file to be immutable, meaning you can't modify or delete it, but 
there's no support I know of for automatically creating a new copy with the 
changes that are made to it and keeping the old one around if its needed.

Jonathan