diskimage-builder/elements/redhat-common/pre-install.d/15-remove-grub
Evgeny Antyshev 8349f0350e Remove grub2 in redhat-common/pre-install.d/15-remove-grub
In Id1e430e7d050a0b99ac449e2ea435e06cda1c4e6 I made the mistake of not
actually removing grub in 15-remove-grub.

This restores the removal phase and adds a bunch of comments.  It
seems the centos7 and centos (6) images have grub2 installed, but F22
does not; hence the check.

For anyone interested in the history; it seems the whole idea of
removing grub and re-installing it in the finalise stage is to do with
Ubuntu grub scripts failing in the chroot.  It is not clear this does,
or has ever, affected rpm based systems; but that's how it is, so
leave well enough alone.

The whole reasoning behind the rpm download & re-install is actually
explained in If095adc4abb52a19a3aa0b1caebfb3e4d8f605ef, but over time
the comments got lost as code moved around.  I've restored in here
some detailed explaination of why we don't just re-install the package
"normally".  I've also added a note to the pre-install of various
things that are related to this step.  Again I think there are some
questions around this that we can investigate in another change.

Change-Id: I1acd19da8567ab93b5003caf67673cc70efea5fa
2015-09-02 15:15:13 +10:00

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#!/bin/bash
if [ "${DIB_DEBUG_TRACE:-0}" -gt 0 ]; then
set -x
fi
set -eu
set -o pipefail
# grub2 isn't available on rhel6/centos6; they are setup to use
# extlinux. skip this
# you would think we could match on $DISTRO or something else; but
# we can't because the rhel/centos elements are a bit mixed up;
# centos-minimal for example sets distro to "centos". so the best
# check is just for the original "grub-install" script
if [ -f /sbin/grub-install ]; then
exit 0
fi
# remove grub2 package. As described in
# elements/ubuntu/pre-install.d/00-remove-grub; the grub post-kernel
# install hook will barf if the block device can't be found (as
# happens in a chroot).
#
# XXX : it is not clear this is necessary for fedora/centos7 and it's
# install hooks. Investigation is required.
if rpm -q grub2; then
install-packages -e grub2
fi
# now configure things to re-install grub at the end. We don't want
# to rely on vm/finalise.d/51-bootloader to simply reinstall the
# package via the package-manager, because at that point (during
# finalise) the build-time yum-cache has been unmounted (hence the
# local-cache looks empty) and yum may try to repopulate the
# local-cache with all the grub2 dependencies. This is slow, and
# potentially fills up the disk.
#
# XXX : At this point, keepcache=0 *should* probably be set for
# yum/dnf. We have not standarised/documented that this will be done,
# however. This would *probably* stop dependencies being populated
# into the cache. We could investigate this, and possibly remove this
# all together if we standardise some of these behaviours.
# So we download the latest grub2 package and setup the install script
# to just install the single-package, which will be called later by
# vm/finalise.d/51-bootloader
install-packages -d /tmp/grub grub2
echo "rpm -i /tmp/grub/*.rpm" > /tmp/grub/install