Init.c, making it chroot

[Oliver Fromme]

Erik Udo wrote:
 > How can i make init chroot after executing /etc/rc, and executing 
 > /etc/rc again in the chrooted enviroment?
 > 
 > For this to work, i'd like to know at what point do i call chroot(), 
 > becouse init.c uses fork() at the point where it runs the rc script.
 > 
 > The thing is, i want to run a whole system in a chrooted enviroment in 
 > this livecd i'm making. But the command "chroot /mnt/root /etc/rc" 
 > returns after the /etc/rc has been run, dropping me back from the 
 > chrooted enviroment. And if it doesn't, init never starts the multiuser 
 > mode.

That's exactly the problem I had when I created a combined
DVD-ROM with FreeBSD and DragonFly BSD on it.  For them to
share the same ISO-9660, at least one of them needed to be
chrooted.  I decided to add the feature to DragonFly BSD's
init(8) because the DragonFly people seemed to be easier to
convince of the usefulness.  ;-)   Indeed, the feature was
committed quickly.  I didn't try to send-pr a similar patch
for FreeBSD.

It shouldn't be too difficult to port it, though:

http://www.dragonflybsd.org/cvsweb/src/sbin/init/init.c

The chroot() patch has been committed with r1.6.  It uses
kenv to specify the chroot directory, so it can easily be
set by the loader(8), e.g. using a custom boot menu.

Best regards
   Oliver

PS:  I see NetBSD has a similar feature, too.  Maybe
FreeBSD should join the crowd and adopt it.  ;-)

-- 
Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
Any opinions expressed in this message may be personal to the author
and may not necessarily reflect the opinions of secnetix in any way.

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leads to lotsa neat pointer tricks; APL mistakes everything for an
array, leading to neat one-liners; and Perl confuses everything
period, making each line a joyous adventure <wink>.
        -- Tim Peters