Lots of tweaks to the install-chroot.sh and install-build-deps.sh

Lots of tweaks to the install-chroot.sh and install-build-deps.sh
script to make them more userfriendly.

In particular, we now recognize systems that have multiple filesystems
(e.g. /home on NFS) and offer to do the right thing.

We also have better support for new Ubuntu distributions (both as
host and as guest). This means, we can now test on "precise".

Added a lot of extra error handling to catch common problems and either
fix them or offer suggestions on how the user can fix them. For example,
we now detect if the user tries to re-install the same chroot environment
multiple times; and we then offer to delete or overwrite the old
installation.

We also detect if a chroot environment is still in active use, and then
refuse to damage it.

In order to help users, who accidentally left an old chroot enviroment
running, we have added a "clean up" option to the wrapper script.

We automatically invoke install-build-deps.sh from install-chroot.sh,
so users only need to run install-chroot.sh and then answer a couple
of questions.

BUG=none
TEST=run install-chroot.sh on a Ubuntu machine and install both lucid32 and precise32. Verify that afterwards, we can build Chrome inside the chroot.
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=126957

[Michael Moss, 2012-03-15 17:35:37]

LGTM++ with a couple nits.

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh
File build/install-chroot.sh (right):

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:17: admin=$(grep '^admin:' /etc/group >&/dev/null &&
echo admin || echo adm)
nit: 'grep -q' (and maybe -s) is preferred elsewhere in this script, even though
the redirect is more portable.

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:43: echo "Invalid -l option(s)"
typo: Invalid -b option(s)

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:102: grep "^\[${i%bit}\]\$" /etc/schroot/schroot.conf
>&/dev/null || continue
nit: same thing with the -q

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:261: head -n26)"
Maybe add to the comment above that we limit it to 26 for convenience of
"lettering" the choices below. It took a minute to figure out why you were
trying to give me DOS limitation flashbacks.

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:374: echo '/media /media none rw,bind 0 0' |
This should probably be rbind, since these things are mounted in dirs under
/media. Just binding /media won't make the submounts available.

[Markus (顧孟勤), 2012-03-15 18:20:09]

I made the changes that you ask for, and will commit.

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh
File build/install-chroot.sh (right):

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:17: admin=$(grep '^admin:' /etc/group >&/dev/null &&
echo admin || echo adm)
Fair enough. Normally, I tend to avoid -q and -s, as they are both unportable
and IMHO less readable than redirections. But I really don't feel particularly
strongly.

This code is by definition very specific to Linux; in fact, very specific to
Ubuntu/Debian. So, I don't think we really need to worry about portability as
much as we would worry in other scripts.

I found all occurrences of "grep" and switched them over to using -q and -s.

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:43: echo "Invalid -l option(s)"
Thanks!

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:261: head -n26)"
Done

https://chromiumcodereview.appspot.com/9702047/diff/1/build/install-chroot.sh...
build/install-chroot.sh:374: echo '/media /media none rw,bind 0 0' |
Very good call :-) Yes, that would never have worked as intended.