From: Ingo Molnar <mingo@elte.hu>
Date: Wed, 20 Apr 2005 07:49:48 GMT
Subject: Re: enforcing DB immutability
Message-ID: <20050420074948.GA22620@elte.hu>
In-Reply-To: <20050420074053.GA22436@elte.hu>


* Ingo Molnar <mingo@elte.hu> wrote:

> perhaps having a new 'immutable hardlink' feature in the Linux VFS 
> would help? I.e. a hardlink that can only be readonly followed, and 
> can be removed, but cannot be chmod-ed to a writeable hardlink. That i 
> think would be a large enough barrier for editors/build-tools not to 
> play the tricks they already do that makes 'readonly' files virtually 
> meaningless.

immutable hardlinks have the following advantage: a hardlink by design 
hides the information where the link comes from. So even if an editor 
wanted to play stupid games and override the immutability - it doesnt 
know where the DB object is. (sure, it could find it if it wants to, but 
that needs real messing around - editors wont do _that_)

i think this might work.

(the current chattr +i flag isnt quite what we need though because it 
works on the inode, and it's also a root-only feature so it puts us back 
to square one. What would be needed is an immutability flag on 
hardlinks, settable by unprivileged users.)

	Ingo