[RFC] Support for using multiple CDs during installation

From: Frans Pop <elendil(at)planet.nl>
Date: Thu Oct 25 2007 - 09:52:06 EDT

Attached patches to apt-setup and pkgsel make it possible to scan multiple CD/DVDs from a set during apt-setup and use them during pkgsel.

The patches have been tested and work. I've done several successful desktop installations using CD1 plus CD2.
However, the patches are still a bit rough and there are some issues that need discussion.

The main issue with the current patches is the new dialogs. Comments on them and suggestions for improvement are welcome.

If those are fixed, the patches could be considered for inclusion even though there are some remaining issues (see below). I'm unsure myself whether any of these issues is serious enough to prevent inclusion.

Changes by the patch

---

Scanning for extra CDs is only supported: - if the installation CD is a full CD or DVD - if the installation method is not hd-media

The apt-setup generator 50cdrom has been moved to 40cdrom; a new generator 41cdset was added to allow scanning of additional CDs. The generator for mirror sources run after that.

When base-config was integrated into D-I, we had find a way to make tasksel install from CD images for hd-media installations. This was solved by bind mounting the CD into target and telling apt-cdrom not to mount/unmount CDs. In the patch for apt-setup this is reverted: apt-cdrom is allowed to mount CDs again. Note that base-installation is not changed in any way.

For CD changing by apt-cdrom in /target to be possible, the installation CD has to be unmounted in the D-I environment. While it is unmounted, no udeb installations are possible.
Both in apt-setup (after scanning additional CDs) and in pkgsel (after tasksel) the installation CD is mounted again so other installation steps do not break.

Remaining issues

---

After the change to the 2nd CD in pkgsel, the progress bar starts at 0 again instead of continuing from its old position.

The prompt for CD changing works during pkgsel, but apparently not for a normal apt-install. During initial tests, installation of grub failed because CD2 was still mounted and I never got the prompt to change CDs. This is worked around by making sure CD1 is installed again, but if any packages from other CDs are needed for whatever reason _after_ pkgsel, the installation will hang for the same reason. I've not really looked yet at why this does not work.

The mechanism to mount the CD again for the D-I environment is somewhat fragile, for two reasons:
- installation of extra udebs is now not possible during pkgsel; this is   not a serious limitation as in practice this is probably not needed - if a CD change is needed to install a package _after_ pkgsel, this will   fail because the CD is mounted in the D-I environment (the CD drive is   locked)
It would be much better if anna or udpkg could detect that the CD is not mounted and ask for it to be mounted when needed and then automatically unmount it again after use so not to interfere with CD changing in /target.

During my tests, the first mount of a CD after changing it would consistently fail. This is probably a bug in VirtualBox. I've added a workaround for this to make working on this a bit easier, but that should probably be removed.

Cheers,
FJP

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text/x-diff attachment: multi-cd_apt-setup.patch



text/x-diff attachment: multi-cd_pkgsel.patch



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Received on Thu Oct 25 09:52:37 2007