Arch Linux pacman hook to automatically recreate syslinux and MBR after updates. This hook is intended to work with quico.space/quico-os-setup/arch-zbm, a root-on-ZFS installation script that uses ZFSBootMenu as its boot loader.

Setup

Not explicitly listed here as a step but still relevant: This pacman hook only makes sense if you're using Syslinux as your boot loader and have the homonymous syslinux package installed.

Get started like so:

Install dependencies jq and rsync
Clone repo into arbitrary path <repo>

Make pacman-zbm-syslinux-regen.sh executable

chmod +x <repo>/pacman-zbm-syslinux-regen.sh

Symlink to files, for example
```
sudo ln -s <repo>/pacman-zbm-syslinux-regen.sh /usr/local/bin/pacman-zbm-syslinux-regen
sudo ln -s <repo>/pacman-zbm-syslinux-regen.hook /usr/share/libalpm/hooks/pacman-zbm-syslinux-regen.hook
```
Note that while you may choose an arbitrary location for your shell script symlink pacman-zbm-syslinux-regen.hook file references /usr/local/bin/pacman-zbm-syslinux-regen. Change that accordingly if you need to.

What's it do?

In pacman whenever the syslinux package is getting updated this hook will replace all *.c32 COMBOOT module files in /boot/syslinux, will reinstall newest extlinux and write the newest mbr.bin Master Boot Record file onto the boot disk.

This happens as a PostTransaction in pacman.

We identify the boot disk via:

findmnt --noheadings --target "${boot_dir}" --output 'SOURCE'

Where "${boot_dir}" is:

boot_dir='/boot/syslinux'

If this returns zero or more than one mounted drive we bail, print an error message and do not do any operations.

Assumptions

Per headline this hook is intended to work with quico.space/quico-os-setup/arch-zbm; it's specifically intended for use on arch-zbm machines that use legacy BIOS. Before using this hook for any other purpose please closely review what it does and adapt to your use case as needed.

We do not care about pacman events other than a syslinux package update. Specifically if ZFSBootMenu gets an update syslinux and our Master Boot Record remain unaffected. Kernel update? Same, no change needed since no kernel or module change directly influence the simple and decoupled structure of syslinux.

Development

Conventional commits

This project uses Conventional Commits for its commit messages.

Commit types

Commit types besides fix and feat are:

build: Project structure, directory layout, build instructions for roll-out
refactor: Keeping functionality while streamlining or otherwise improving function flow
test: Working on test coverage
docs: Documentation for project or components

Commit scopes

The following scopes are known for this project. A Conventional Commits commit message may optionally use one of the following scopes or none:

script: Work related to the commands triggered by pacman
hook: Configuring the hook(s)
meta: Affects the project's repo layout, readme content, file names etc.