dpkg-divert grub-probe binary to avoid problems in OpenVZ environments

It's a hard to debug problem as it doesn't seem to be
reproducible in every OpenVZ environment and on the other hand
makes the system unusable as soon as the bug is triggered. :(

On the command line/in the logs you'll notice something like
that before the system is becoming unuseable:

| Setting up grub-common (1.99-22.1) ...
| Setting up grub2-common (1.99-22.1) ...
| Setting up grub-pc-bin (1.99-22.1) ...
| Setting up grub-pc (1.99-22.1) ...
|
| Creating config file /etc/default/grub with new version
| grub-probe: error: cannot find a device for / (is /dev mounted?).
| grub-probe: error: cannot find a device for /boot (is /dev mounted?).
| grub-probe: error: cannot find a device for /boot/grub (is /dev mounted?).

To avoid grub-probe being executed during software installation
let's dpkg-divert the binary during the FAI dirinstall process
through the existing hook script instsoft.GRMLBASE. Then revert
the dpkg-divert via scripts/GRMLBASE/98-clean-chroot before
actually building the ISO again.

While at it also divert update-grub in the same code path as
well.

diff --git a/etc/grml/fai/config/hooks/instsoft.GRMLBASE b/etc/grml/fai/config/hooks/instsoft.GRMLBASE
index ea1cfd0..65da202 100755 (executable)
--- a/etc/grml/fai/config/hooks/instsoft.GRMLBASE
+++ b/etc/grml/fai/config/hooks/instsoft.GRMLBASE
@@ -48,6 +48,13 @@ EOF
      $ROOTCMD ln -s /bin/true /usr/sbin/update-grub
    fi
 
+   # work around a bug which causes openvz to freeze when grub-probe is invoked
+   if ! $ROOTCMD dpkg-divert --list | grep -q '/usr/sbin/grub-probe' ; then
+     echo "Diverting grub-probe executable"
+     $ROOTCMD dpkg-divert --rename --add /usr/sbin/grub-probe
+     $ROOTCMD ln -s /bin/true /usr/sbin/grub-probe
+   fi
+
   # newer aptitude versions won't remove essential packages using
   # 'aptitude -f -y install file-rc' anymore, therefore force it:
   $ROOTCMD aptitude -o Aptitude::ProblemResolver::Keep-All-Tier=60000 -f -y install file-rc
@@ -83,6 +90,21 @@ fi
 # no softupdate but fresh installation
 echo "Action $FAI_ACTION of FAI (hooks/instsoft.GRMLBASE) via grml-live running"
 
+# work around /etc/kernel/postinst.d/zz-update-grub failing
+# inside openvz environment, see #597084
+if ! $ROOTCMD dpkg-divert --list | grep -q '/usr/sbin/update-grub' ; then
+  echo "Diverting update-grub executable"
+  $ROOTCMD dpkg-divert --rename --add /usr/sbin/update-grub
+  $ROOTCMD ln -s /bin/true /usr/sbin/update-grub
+fi
+
+# work around a bug which causes openvz to freeze when grub-probe is invoked
+if ! $ROOTCMD dpkg-divert --list | grep -q '/usr/sbin/grub-probe' ; then
+  echo "Diverting grub-probe executable"
+  $ROOTCMD dpkg-divert --rename --add /usr/sbin/grub-probe
+  $ROOTCMD ln -s /bin/true /usr/sbin/grub-probe
+fi
+
 # make sure we have file-rc available before package_config/GRML* is being executed {{{
 # the apt-get update might return an error if there's for example
 # a hashsum mismatch on Debian mirror sources, we might want to continue

diff --git a/etc/grml/fai/config/scripts/GRMLBASE/98-clean-chroot b/etc/grml/fai/config/scripts/GRMLBASE/98-clean-chroot
index 1a736ee..19464a2 100755 (executable)
--- a/etc/grml/fai/config/scripts/GRMLBASE/98-clean-chroot
+++ b/etc/grml/fai/config/scripts/GRMLBASE/98-clean-chroot
@@ -35,6 +35,14 @@ if $ROOTCMD dpkg-divert --list | grep -q '/usr/sbin/update-grub' ; then
   $ROOTCMD dpkg-divert --rename --remove /usr/sbin/update-grub
 fi
 
+# revert dpkg-divert of hooks/instsoft.GRMLBASE, which is
+# used to work around a grub-probe<->openvz bug
+if $ROOTCMD dpkg-divert --list | grep -q '/usr/sbin/grub-probe' ; then
+  echo "Undoing dpkg-divert of grub-probe executable"
+  $ROOTCMD rm -f /usr/sbin/grub-probe
+  $ROOTCMD dpkg-divert --rename --remove /usr/sbin/grub-probe
+fi
+
 # revert udev workaround of hooks/updatebase.GRMLBASE
 if grep -q 'updatebase.GRMLBASE' ${target}/etc/udev/kernel-upgrade 2>/dev/null ; then
   echo "Removing /etc/udev/kernel-upgrade created by updatebase.GRMLBASE"