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From: Herbert P÷tzl (herbert_at_13thfloor.at)
Date: Mon 11 Aug 2003 - 19:06:50 BST


On Mon, Aug 11, 2003 at 04:47:31PM +0100, Sam Vilain wrote:
>
> Opinion Poll!
>
> let's assume each file and directory carry a tag which
> says "this is a file of context N", where N is the context
> number of a virtual server.

Hi Sam!

maybe you should have a look at the archives ...

> An idea I just had is to treat it like an extension to the user ID -
> eg, if you are using 16 bit user IDs then the context + the uid is the
> `system userid' of 32 bits, but with special behaviour (such as
> setting a default, meaning `any context', etc) when the context part
> is 0 or 1. That way, files are uniquely identifiable between
> contexts.

wow! great idea, and it actually works, or at least seems
to, as I use it since october 2002 ... 8-)

http://www.13thfloor.at/VServer/Concepts.shtml

> btw, where would you put those extra bits for each inode, is there
> room in the ext2/reiser/etc reserved structures? Of course you could
> use the top half of the nice shiny 32-bit UIDs in Linux 2.6 :-)

> This would mean adding syntax to `chown' and/or `chgrp' to specify a
> context name as well as a username (eg, chown root_at_vs1:other_at_vs1
> filename).

http://vserver.13thfloor.at/Linux2.6/index.php?page=Per+Context+Quota

there you have the chctx/lsctx tools too ... what a
surprise *g* ...

> It could also be a different command, chctx, as suggested elsewhere.
> But personally, it looks like ownership to me.
>
> 2) if a program of context N encounters a file of
> context M, where N != M ...
>
> a) on modify change the file to the new context?
> b) do not allow access to files from other contexts
> except context zero/one?
> c) allow modification while keeping the file
> in its 'original' context?
>
> 3) consider a program creating a (hard)link to a file
> in another context (including zero/one), should ...
>
> a) the file change to the 'new' context?
> b) the file keep the old context?
> c) this operation be disallowed?
>
> 4) consider a program removing a link to a file with
> more than one links, should the remaining links ...
>
> a) be still 'owned' by the removing context?
> b) be changed to context zero/one?
>
> The behaviour should be exactly as if it were owned by a different
> user.

objection, the least thing to consider is
root in different contexts, which you do not
want to be handled like 'normal' users ...

best,
Herbert

> --
> Sam Vilain, sam_at_vilain.net
>
> C++, where only your friends can access your private parts.
>


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