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Diffstat (limited to 'hooks/merged-usr/setup00.sh')
| -rwxr-xr-x | hooks/merged-usr/setup00.sh | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/hooks/merged-usr/setup00.sh b/hooks/merged-usr/setup00.sh new file mode 100755 index 0000000..a6b08d2 --- /dev/null +++ b/hooks/merged-usr/setup00.sh @@ -0,0 +1,79 @@ +#!/bin/sh +# +# mmdebstrap does have a --merged-usr option but only as a no-op for +# debootstrap compatibility +# +# Using this hook script, you can emulate what debootstrap does to set up +# merged /usr via directory symlinks, even using the exact same shell function +# that debootstrap uses by running mmdebstrap with: +# +# --setup-hook=/usr/share/mmdebstrap/hooks/merged-usr/setup00.sh +# +# Alternatively, you can setup merged-/usr by installing the usrmerge package: +# +# --include=usrmerge +# +# mmdebstrap will not include this functionality via a --merged-usr option +# because there are many reasons against implementing merged-/usr that way: +# +# https://wiki.debian.org/Teams/Dpkg/MergedUsr +# https://wiki.debian.org/Teams/Dpkg/FAQ#Q:_Does_dpkg_support_merged-.2Fusr-via-aliased-dirs.3F +# https://lists.debian.org/20190219044924.GB21901@gaara.hadrons.org +# https://lists.debian.org/YAkLOMIocggdprSQ@thunder.hadrons.org +# https://lists.debian.org/20181223030614.GA8788@gaara.hadrons.org +# +# In addition, the merged-/usr-via-aliased-dirs approach violates an important +# principle of component based software engineering one of the core design +# ideas/goals of mmdebstrap: All the information to create a chroot of a Debian +# based distribution should be included in its packages and their metadata. +# Using directory symlinks as used by debootstrap contradicts this principle. +# The information whether a distribution uses this approach to merged-/usr or +# not is not anymore contained in its packages but in a tool from the outside. +# +# Example real world problem: I'm using debbisect to bisect Debian unstable +# between 2015 and today. For which snapshot.d.o timestamp should a merged-/usr +# chroot be created and for which ones not? +# +# The problem is not the idea of merged-/usr but the problem is the way how it +# got implemented in debootstrap via directory symlinks. That way of rolling +# out merged-/usr is bad from the dpkg point-of-view and completely opposite of +# the vision with which in mind I wrote mmdebstrap. + +set -eu + +if [ "${MMDEBSTRAP_VERBOSITY:-1}" -ge 3 ]; then + set -x +fi + +TARGET="$1" + +# now install an empty "usr-is-merged" package to avoid installing the +# usrmerge package on this system even after init-system-helpers starts +# depending on "usrmerge | usr-is-merged". +# +# This package will not end up in the final chroot because the essential +# hook replaces it with the actual usr-is-merged package from src:usrmerge. + +tmpdir=$(mktemp --directory --tmpdir="$TARGET/tmp") +mkdir -p "$tmpdir/usr-is-merged/DEBIAN" + +cat << END > "$tmpdir/usr-is-merged/DEBIAN/control" +Package: usr-is-merged +Priority: optional +Section: oldlibs +Maintainer: Johannes Schauer Marin Rodrigues <josch@debian.org> +Architecture: all +Multi-Arch: foreign +Source: mmdebstrap-dummy-usr-is-merged +Version: 1 +Description: dummy package created by mmdebstrap merged-usr setup hook + This package was generated and installed by the mmdebstrap merged-usr + setup hook at /usr/share/mmdebstrap/hooks/merged-usr. + . + If this package is installed in the final chroot, then this is a bug + in mmdebstrap. Please report: https://gitlab.mister-muffin.de/josch/mmdebstrap +END +dpkg-deb --build "$tmpdir/usr-is-merged" "$tmpdir/usr-is-merged.deb" +dpkg --root="$TARGET" --log="$TARGET/var/log/dpkg.log" --install "$tmpdir/usr-is-merged.deb" +rm "$tmpdir/usr-is-merged.deb" "$tmpdir/usr-is-merged/DEBIAN/control" +rmdir "$tmpdir/usr-is-merged/DEBIAN" "$tmpdir/usr-is-merged" "$tmpdir" |