Re: How do I mount the USB stick containing the installer in Rescue Mode?

From	David Wright <deblis@lionunicorn.co.uk>
Newsgroups	linux.debian.user
Subject	Re: How do I mount the USB stick containing the installer in Rescue Mode?
Date	2021-07-16 06:50 +0200
Message-ID	<CBnXs-6Cc-3@gated-at.bofh.it> (permalink)
References	<CBeKu-Io-1@gated-at.bofh.it> <CBfnb-1ch-1@gated-at.bofh.it> <CBfZT-1F8-7@gated-at.bofh.it>
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On Thu 15 Jul 2021 at 22:19:23 (+0200), Stella Ashburne wrote:
> > Sent: Thursday, July 15, 2021 at 7:30 PM
> > From: "Thomas Schmitt" <scdbackup@gmx.net>
> >
> > Well, since the case "already mounted" is quite outruled, it might be time
> > to explore "mount point busy".
> >
> >   https://codesearch.debian.net/search?q=package%3Autil-linux+already+mounted+or+mount+point+busy
> > shows that mount(8) emits this message if it gets error code EBUSY.
> > It is not so clear from where this code comes, but mount(2) would be a
> > fine candidate (or placeholder).
> 
> In Rescue Mode, it's impossible for me to install packages such as the one whose link you had provided.
> >
> > So does it work with some other, newly created directory instead of /mnt ?
> >
> 
> No, it doesn't work with other newly created directories in addition to /mnt.

I can tell you why you can't mount it, but you're swimming in waters
too deep for me, so I can't tell you the "proper" way¹ to circumvent
the problem. Others probably can. I'll just suggest a workaround
(untested).

OK, you've just asked for a shell on /dev/perfect-vg/root which is the
root filesystem on your new installation. But up until this point,
the rescue root filesystem was in memory, created when you booted from
the stick. The rescue stick itself (/dev/sdb1) was mounted on /cdrom.
Your problem is: all that is still true, and it's still mounted there.

If you press Alt-F2, or Alt-F3 (or use Alt-arrows to achieve the
same), you can run a shell in the original rescue environment.
(You could actually have started one much earlier after booting.)

Type:
# mount
in *this* shell and you will see   /dev/sdb1 on /cdrom   in the list,
and that is the installation/rescue stick's mountpoint.

If you list /cdrom, you'll see /dists/ and /pool/ in there, which is
how repositories normally present themselves. The symlink debian->.
enables "debian" to be used as the name of the $ARCHIVE_ROOT,
thereby containing debian/dists/.

You should also see   /dev/perfect-vg/root on /target   in the list,
and /target is where your new root filesystem resides (as seen from
the Alt-F1 point of view).

To summarise, Alt-F2 and Alt-F3 shells show you the root filesystem
of the rescue environment (all the time), whereas Alt-F1 shows you
a root filesystem rooted at whatever you chose in the dialogue box.
This Alt-F1 root sits under /target in the Alt-F2 and Alt-F3 shells.

In this situation, my workaround would be (in Alt-F1) to create a
directory called /home/debian/.² You can now (in Alt-F2or3) copy
/dists and /pool into /target/home/debian/ which will make the
repository on the stick available in Alt-F1: the $ARCHIVE_ROOT
will be just /home/debian/.

BTW If you're wondering what Alt-F4 is, it's the system log: the
tail of of the file /var/log/syslog (as seen from Alt-F2or3).

¹ Perhaps some sort of bind mount?

² I'm assuming your own username is not debian, so it won't collide
  with your own home directory.

Cheers,
David.

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