[lmi] Creating an lmi schroot from scratch [Was: wx-dependent gcc warnings]

[Greg Chicares]

On 2020-06-09 15:27, Vadim Zeitlin wrote:
> On Tue, 9 Jun 2020 11:41:24 +0000 Greg Chicares <gchicares@sbcglobal.net> 
> wrote:
> 
> GC> > And of course it's easy to find all diagnostics that are inhibited
> GC> > by '-isystem' for wx, by moving one line:
> 
>  BTW, I'm still not sure what exactly should I do to build lmi in its own
> chroot so that it doesn't interfere with anything in my main system (and
> notably doesn't require me to install anything into /opt or anywhere
> outside of my home directory), which is why I hadn't done this myself. I'm
> waiting for the stabilization of the lmi build scripts before trying to do
> it, could you please let me know when should I try to test them?

I think this will work for you:

su
cd /tmp
wget -N -nv https://git.savannah.nongnu.org/cgit/lmi.git/plain/lmi_setup_00.sh
chmod +x lmi_setup_00.sh
time flavor=centos ./lmi_setup_00.sh >/srv/cache_for_lmi/logs/chroot_log_$(date 
-u +"%Y%m%dT%H%MZ") 2>&1

It's been my habit to do that as root, but I believe you could just as
well do it as a normal user, adding "sudo" on the last line, e.g.:
  sudo flavor=centos ./lmi_setup_00.sh
It doesn't really matter if you run it with 'time' or redirect output.

I assume you've already installed both 'curl' and 'wget'.

The script that's downloaded manually with wget, uses wget to download
other scripts with similar names. If you have files in /tmp that you
want to preserve, with names matching
  lmi_setup_*.sh
  install_msw.sh
  schroot_env
  .zshrc
  .vimrc
  en.utf-8.add
then this script will overwrite them; I think it's reasonable to assume
that's not a problem.

In 'lmi_setup_02c.sh', I wasn't sure how to avoid accidental harm when
obliterating any previously-created centos chroot, so for safety it
just halts for you. Here's the dangerous code:

grep centos /proc/mounts | cut -f2 -d" " | xargs --no-run-if-empty umount
rm -rf /srv/chroot/centos7lmi
rm /etc/schroot/chroot.d/centos7lmi.conf

especially the first line, which destroys any mount containing the
string 'centos'. I could make that more specific--the mounts that this
script would create are:

  /srv/chroot/centos7lmi/var/cache/yum
  /srv/chroot/centos7lmi/var/cache/bullseye
  /srv/chroot/centos7lmi/srv/cache_for_lmi
  /srv/chroot/centos7lmi/dev/pts
  /srv/chroot/centos7lmi/proc
  /srv/chroot/centos7lmi/srv/chroot/lmi_bullseye_2/var/cache/apt/archives
  /srv/chroot/centos7lmi/srv/chroot/lmi_bullseye_2/srv/cache_for_lmi
  /srv/chroot/centos7lmi/srv/chroot/lmi_bullseye_2/dev/pts
  /srv/chroot/centos7lmi/srv/chroot/lmi_bullseye_2/proc

so I suppose I should grep for "centos7lmi" in /proc/mounts instead.
I'll commit that change locally, and provide an omnibus patch below
including any other changes that occur to me while writing this email.

I'm assuming you're using a debian-based system. Probably the script
should check for that before invoking 'apt-get install rinse', but
that should fail safely on a non-debian system (and all these scripts
use 'set -e', so they halt on failure...but for 'lmi_setup_inc.sh'
(see below), I assume without testing that
  set -evx
  ... "e" is enabled here
  set +vx
  ... "e" is still enabled here
right?).

I assume you won't mind that this suite of scripts installs 'rinse'.
or that it creates:
  /var/cache/centos_lmi/
  /etc/schroot/chroot.d/centos7lmi.conf
  /srv/chroot/
  /srv/cache_for_lmi
All new directories in system directories contain the substring "lmi"
except in /srv : 'schroot' by default creates a /chroot/ directory
there.

These scripts can create a debian-testing chroot directly on a debian
or redhat system, but I'm suggesting you create a debian-within-centos
chroot ("flavor=centos"). The extra overhead isn't much, and it's
nicely isolated: all the potentially-dangerous stuff happens in the
intermediate centos chroot, and you can see it all in advance by
reading
  lmi_setup_00.sh
  lmi_setup_00c.sh
and the couple of short and harmless scripts they run directly
(but see the caution on 'lmi_setup_02c.sh' above). Everything else
is done in a chroot, so your base system is pretty well insulated.

Here's a diff with untested changes described above:

----8<----8<----8<----
diff --git a/lmi_setup_00c.sh b/lmi_setup_00c.sh
index e1f03747..52b4b716 100755
--- a/lmi_setup_00c.sh
+++ b/lmi_setup_00c.sh
@@ -31,6 +31,8 @@ assert_not_chrooted
 
 ./lmi_setup_02c.sh
 
+mkdir -p /etc/schroot/chroot.d
+
 cat >/etc/schroot/chroot.d/centos7lmi.conf <<EOF
 [centos7lmi]
 description=centos-7.7
diff --git a/lmi_setup_02c.sh b/lmi_setup_02c.sh
index 4e30dcb3..5e625653 100755
--- a/lmi_setup_02c.sh
+++ b/lmi_setup_02c.sh
@@ -43,7 +43,7 @@ if [ "greg" != "$(logname)" ]; then
    exit 1
 fi
 
-grep centos /proc/mounts | cut -f2 -d" " | xargs --no-run-if-empty umount
+grep centos7lmi /proc/mounts | cut -f2 -d" " | xargs --no-run-if-empty umount
 rm -rf /srv/chroot/centos7lmi
 rm /etc/schroot/chroot.d/centos7lmi.conf
 
diff --git a/lmi_setup_inc.sh b/lmi_setup_inc.sh
index 5e2b1342..4fa08464 100755
--- a/lmi_setup_inc.sh
+++ b/lmi_setup_inc.sh
@@ -28,7 +28,7 @@
 # Variables defined but unused here: this file should only be sourced.
 # shellcheck disable=SC2034
 
-set -vx
+set -evx
 
 CODENAME=bullseye
 CHRTVER=2
---->8---->8---->8----