Re: [dev][ubase] Implement switch_root

From: Dimitris Papastamos <dp_AT_spl9.org>
Date: Tue, 15 Apr 2014 17:57:25 +0100

On Tue, Apr 15, 2014 at 06:44:54PM +0200, Markus Wichmann wrote:
> On Sun, Apr 13, 2014 at 02:10:51PM +0200, FRIGN wrote:
> > Good day,
> >
> > sometimes, you depend on an initramfs to do stuff for you before
> > the rootfs is available.
> > Busybox has become the standard for "all your initramfs needs", but
> > tbh, I hate working with it.
> > Statically linking sbase and ubase and choosing the tools you need for
> > the job almost solves the problem, but the lack of switch_root, which
> > almost every initramfs depends on, forces you to use busybox (because
> > util-linux doesn't link statically).
> >
> > Now, I would've already sent in a patch, but I am pretty sure somebody
> > here already hacked it together before. So, to save my time, I better
> > ask now.
> >
> > Cheers
> >
> > FRIGN
> >
> > --
> > FRIGN <dev_AT_frign.de>
> >
>
> Why switch_root and not pivot_root? Here's a sh mockup of how to do what
> you wrote with pivot_root:
>
> set -e
> new_root=$1
> put_old=$2
> [ -d $put_old ] || made_dir=1
> mkdir -p $put_old
> cd $new_root
> pivot_root $new_root $put_old
> chroot $new_root
> umount ${put_old#$new_root}
> [ $made_dir ] && rm -rf ${put_old#$new_root}

Because if it is a shell script then it cannot be included in ubase-box
which means that it needs to be maintained separately. Also the existing
build system for ubase/sbase doesn't cope with shell scripts (can be fixed
but not until we have a very good reason).

Cheers,
sin
Received on Tue Apr 15 2014 - 18:57:25 CEST