linux-kernel - Re: ownership/permissions of cpio initrd

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Message-Id: <200612052007.kB5K7ntk023359@laptop13.inf.utfsm.cl>
Date:	Tue, 05 Dec 2006 17:07:49 -0300
From:	"Horst H. von Brand" <vonbrand@....utfsm.cl>
To:	"Marty Leisner" <linux@...hester.rr.com>
cc:	linux-kernel@...r.kernel.org, bug-cpio@....org,
	martin.leisner@...ox.com
Subject: Re: ownership/permissions of cpio initrd 

Marty Leisner <linux@...hester.rr.com> wrote:
> I'm working on an embedded system with the 2.6 kernel -- cpio
> initrd was a new feature I'm looking at (and very welcome).
> 
> The major advantage I see is you don't have MAKE a filesystem
> on the build host (doing cross development).  So you don't have
> to be root.

> But its "useful" to change permissions/ownership of the initrd
> files at times...

> Since a cpio is just a userspace created string of bits, I suppose
> you can apply a set of ownership/permissions to files IN the archive
> by playing with the bits...

The easy way out is to unpack the initrd, fix permissions, and repack. That
requires root, though (it creates devices).

> Does such a tool exist?  Comments?  Seems very useful in order to
> avoid being root...

I'd use sudo(1) + specially cooked commands to unpack/pack an initrd. It is
a bit more work, but gives you extra flexibility (i.e., not just futzing
around with permissions, can also add/replace/edit/rename/delete files, ...
using bog standard tools).
-- 
Dr. Horst H. von Brand                   User #22616 counter.li.org
Departamento de Informatica                    Fono: +56 32 2654431
Universidad Tecnica Federico Santa Maria             +56 32 2654239
Casilla 110-V, Valparaiso, Chile               Fax:  +56 32 2797513
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