Hello all,
First off, apologies if this has been/is being discussed elsewhere, but
this has been on my mind for quite some time.
The state of the systemd mkinitcpio hook has been bothering me recently.
It seems that there is some confusion/ambiguity about what capabilities,
precisely, said hook provides; particularly with regards to replacing
the 'base' hook at some point. I think it's effectively ready now; I've
been using the systemd hook without base and udev for some time now. The
only sticking point seems to be with the rescue and emergency shells.
Of the 19 open systemd bugs [0], four of them [1-4] deal with systemd
not providing an emergency/rescue shell and/or busybox/maintenance tools
to the initrd image. Based on my understanding of the status quo, the
systemd init hook is intended to simplify and streamline the boot
process and the initrd image for systemd-based systems. The hook
currently does this. It does not provide any functional rescue
capabilities (you can get to an emergency shell, but it doesn't work),
and I don't think it should. The use case for initrd-based rescue shells
is very small and specific; many of these use cases can make do with a
live image or something similar.
Basically, my view is this: the systemd hook should only provide boot
functionality, and not contain rescue/emergency targets/shells by
default. The problem with providing such functionality is that the
dependencies and binary include requirements quickly spiral out of
control when providing a full shell within the initrd (sulogin, busybox,
any rescue tools, etc). Having so many dependencies goes against the
simplicity that the systemd hook is trying to accomplish.
If anything, I propose a new hook, sd-rescue, which provides
rescue.{target,service}, emergency.{target,service}, busybox, and
minimal binaries useful for rescuing a system. This can be used in
situations where live-image booting is not an option, or where the
sysadmin prefers the option of initrd emergency/rescue functions. Also,
we should maybe stop including emergency.target with the systemd hook,
since it doesn't seem to work in most cases.
-- Chris
[0] https://bugs.archlinux.org/?project=1&cat%5B%5D=31&string=systemd
[1]
https://bugs.archlinux.org/task/44493?project=1&cat%5B0%5D=31&string=systemd
[2]
https://bugs.archlinux.org/task/45480?project=1&cat%5B0%5D=31&string=systemd
[3]
https://bugs.archlinux.org/task/42399?project=1&cat%5B0%5D=31&string=systemd
[4]
https://bugs.archlinux.org/task/36265?project=1&cat%5B0%5D=31&string=systemd
