chattr

[pll at lanminds.com]

In a message dated: Wed, 29 Jan 2003 22:18:43 EST
bscott at ntisys.com said:

>  The problem I describe is only with the immutable bit.  Consider the
>fairly common scenario of a full backup, followed by an incremental backup.  
>You wish to restore said backups.  What is the right thing to do if an
>immutable file is contained within both the full and the incremental
>savesets?

In theory, the immutable file should never make it an incremental 
backup.  Since it can not, by definition, be changed, it should be 
exactly the same at the time the incremental is run as it was when 
the last full was run, and therefore be bypassed.  Ergo, not a 
problem at all :)

If someone comes along between a full and incremental, changes the 
immutable setting, then the file, and resets the immutable bit,
*then* you have a problem.  The solution to that is to shoot the 
person who did this :)

>It should be restored from the incremental saveset, because that
>is the most recent version; at the same time, the system should not allow
>the immutable file from the original saveset to be modified.  That is, after
>all, the point of the immutable bit; programatically overriding that
>behavior defeats the purpose.

In this basic scenario, as I said, it would never be on the 
incremental.  If however, someone came along in the scenario I 
proposed above, *then* there is this problem, and as also stated, the 
real solution is a public lynching for the guilty :)

>  An idea that appeals to me is to never backup or restore the immutable
>bit.  When setting the bit in the first place, instead of doing so directly,
>create a list of files to be set immutable, and feed that to "chattr +i"  
>automatically.  That list can then be archived with the rest of the
>filesystem, and applied again at the end of a restore.  Of course, this does
>not solve the problem; it simply bypasses it.


I'm really curious how often people play with the immutable bit, and 
for what purposes.  I've always known about it, but never had a 
reason to muck with it.  Why do people use this?  In what scenarios?
-- 

Seeya,
Paul
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