Re: can root somehow create a immutable file in a non-uid-0, hierarchy?

[David G. Miller (aka DaveAtFraud)]

Skunk Worx  wrote:
> fc6 user...basic fs question.
>
> Suppose I am root/UID 0. Is there a way to create a file in someone 
> else's (non-uid-0) FS hierarchy and have it be immutable? No rename, etc.?
>
> I'm trying to do a hot-plug of disk keys and I would like to put some of 
> my own bytes somewhere so I know whether or not I've seen the disk key 
> before.
>
> Some years ago I used SGI machines and they had a file system with a 
> volume header I could use. I don't think extX has such a capability.
>
> I'm pretty sure the answer is no, but I figured I'd ask anyway.
>
> Thanks,
> John

If root creates a file within a user's file hierarchy, the file is owned 
by root but the directory containing the file is still owned by the 
user.  The user can still rename the file since the file name is in the 
directory.  Likewise, the file can be renamed.  About the only thing the 
user can't do is change the file contents.

Cheers,
Dave