[pve-devel] [PATCH 1/3] boot-tool: disarm upstream systemd-boot hookscripts

[Stoiko Ivanov <s.ivanov@proxmox.com>]

With Debian Bookworm systemd-boot is a separate binary-package,
instead of part of the main systemd package.
Since it's not installed by default, Debian-upstream has added
hook-scripts to the package, which manage kernel copying to the esp
(kernel-install).

The hookscripts print a warning if the ESP is not mounted at
$SYSTEMD_ESP_PATH or /boot/efi, /efi or /boot - through `bootctl
is-installed --quiet` [0,1].

This patch adds a function, which disables the hookscripts from
upstream if /etc/kernel/proxmox-boot-uuids is present.
It adds an explanation as marker and 'exit 0' on top of the script, so
that users know why the scripts were touched (e.g. when a new
systemd-boot hookscript version from upstream asks what to do with the
local modifications)

While editing shell-script hooks from other packages is quite brittle
it still seems like the best option, to support most use-cases
(including users, who don't use proxmox-boot-tool, but want to
manually install systemd-boot).
Alternatives considered:
* dpkg-divert for all hookscripts - sadly the Debian policy manual
  warns against this
* adding Replaces: systemd-boot to d/control - afaict this would need
  systemd-boot to also declare this for proxmox-kernel-helper [3]

Tested on 2 VMs installed with the 8.0 ISO (once with legacy once with
uefi boot)

[0]
https://github.com/systemd/systemd/blob/8a38b62f37189b071a30f208530ce5dc278e521e/src/shared/find-esp.c#L503
[1]
https://github.com/systemd/systemd/blob/8a38b62f37189b071a30f208530ce5dc278e521e/src/boot/bootctl.c#L90
[2] https://www.debian.org/doc/debian-policy/ap-pkg-diversions.html
[3] https://www.debian.org/doc/debian-policy/ch-relationships.html

Reported-by: Aaron Lauterer <a.lauterer@proxmox.com>
Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
---
 src/proxmox-boot/zz-proxmox-boot | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/proxmox-boot/zz-proxmox-boot b/src/proxmox-boot/zz-proxmox-boot
index c6c708c..c72f9ef 100755
--- a/src/proxmox-boot/zz-proxmox-boot
+++ b/src/proxmox-boot/zz-proxmox-boot
@@ -191,6 +191,27 @@ remove_old_kernels_legacy() {
 
 }
 
+disable_systemd_boot_hook() {
+
+	if [ ! -f "${ESP_LIST}" ]; then
+		return
+	fi
+
+	marker="# This hookfile has been disabled by proxmox-boot-tool"
+	for hookfile in \
+		"/etc/initramfs/post-update.d/systemd-boot" \
+		"/etc/kernel/postinst.d/zz-systemd-boot" \
+		"/etc/kernel/postrm.d/zz-systemd-boot" ; \
+	do
+		grep -q "$marker" "$hookfile" && continue
+		warn "	Disabling upstream hook $hookfile"
+		printf "#!/bin/sh\n\n%s\nexit 0\n" "$marker" > "$hookfile.pbt.tmp"
+		cat "$hookfile" >> "$hookfile.pbt.tmp"
+		mv "$hookfile.pbt.tmp" "$hookfile"
+	done
+
+}
+
 set -- $DEB_MAINT_PARAMS
 mode="${1#\'}"
 mode="${mode%\'}"
@@ -203,12 +224,14 @@ case $0:$mode in
 		reexec_in_mountns "$@"
 		BOOT_KVERS="$(boot_kernel_list "$@")"
 		update_esps
+		disable_systemd_boot_hook
 	;;
 	 */postrm.d/*:|*/postrm.d/*:remove)
 		reexec_in_mountns "$@"
 		# no newly installed kernel
 		BOOT_KVERS="$(boot_kernel_list)"
 		update_esps
+		disable_systemd_boot_hook
 	;;
 esac
 
-- 
2.30.2