This is a set of pacman hooks and systemd units to preserve the running
kernel's modules during upgrades.  If one upgrades the kernel but
doesn't reboot right away, any modules that were not loaded yet are
lost.  Modules are often loaded dynamically due to hardware being
hotplugged at runtime (e.g. a USB device).  While it's recommended to
reboot immediately after an upgrade, sometimes it's inconvenient.  On
the next boot, any saved kernels are purged.

* /usr/share/libalpm/hooks/50-save-kernel-modules-pre.hook
  PreTransaction hook.  Should be before 60 because of mkinitcpio-remove and dkms-remove.

* /usr/share/libalpm/hooks/90-save-kernel-modules-post.hook
  PostTransaction hook.  Should be after 70 because of dkms-install.

* /usr/lib/modules/saved-kernel-modules/modules/
  Where the modules are preserved

* /usr/lib/modules/saved-kernel-modules/pre-hook
  Pacman hook to save the running kernel

* /usr/lib/modules/saved-kernel-modules/pre-hook
  Pacman hook to link the running kernel back in to /usr/lib/modules/

* /usr/lib/modules/saved-kernel-modules/cleanup
  Script to clean any saved kernels on the next boot

* /usr/lib/systemd/system/saved-kernel-modules.service
  Runs cleanup on the next boot

* /usr/lib/systemd/system/saved-kernel-modules.timer
  Schedules the clean up