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godzillaknight

Member

Registered: 2022-07-19

Posts: 8

[SOLVED] iMac/Arch dual boot (systemd) reinstallation

Hello everyone, Arch newbie here.
I have successfully dual booted Arch and macOS on an old iMac 2009, following ArchWiki guide. And everything works fine. I understand macOS and Arch share the same boot partition (systemd bootloader per ArchWiki recommendations). My question is:
If I ever want to start again from scratch, i.e deleting old Arch installation partition, reinstalling Arch, what happens to the systemd bootloader that is currently installed in the shared boot partition?  Will it be removed during deletion of old Arch partition or does it simply stay there (I'm incline to think this is likely)? If so, should I simply install systemd bootloader again (bootctl --path=/boot install) during re-installation? If so, will there be conflicts between old and new systemd installation? Or, am I way off in this?
I'd be glad if someone could help me clear this up.
Thanks in advance!

Last edited by godzillaknight (2022-07-19 11:21:33)

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 25,266

Re: [SOLVED] iMac/Arch dual boot (systemd) reinstallation

No unless you format the ESP it will just stick around, during installation you could install it that way to get the latest version, or just keep the existing one. The only conflict between old and new installation that could arise if you forgot to mount the ESP partition to /boot before installing a kernel as that way systemd-boot would not find a kernel image to boot.

You can generally create little conflict here, even an older systemd-boot version needs to be able to boot an up to date system. You could check the output of bootctl status to see which kind of systemd-boot features would be missing from your "old" install in comparison to a new one.  You can always update that from an existing system with bootctl update.

Your biggest enemy here is the Mac's EFI implementation and how it reacts to changes in the systemd-boot binary on the ESP. I know too little here, but if there's nothing akin to Secureboot or you explicitly created a exemption for that specific systemd-boot binary then this should not be an issue.

godzillaknight

Member

Registered: 2022-07-19

Posts: 8

Re: [SOLVED] iMac/Arch dual boot (systemd) reinstallation

Thank you so much for the quick reply.

If I understand correctly,

1)  systemd bootloader stays in the shared boot partition (assuming ESP is not formatted). Not only that, if the ESP is mounted to /boot first, followed by "new" Arch installation, then the "old" systemd should be able to boot up the "new" Arch. Also, the "old" systemd can be updated from within the "new" Arch with bootctl --update.

2) assuming the shared ESP is mounted to /boot, installing "new" systemd ( with "bootctl --path=/boot install") is okay and will simply install the latest systemd version. It will replace the "old" systemd.

3) re: Mac's EFI implementation. It's an old OS X Yosemite 10.10.5, end of life, no secure boot, nothing fancy (in fact, a security update got me stuck on startup and won't let me inside mac; had to reinstall Yosemite again). I do not intend to ever update or use mac OS again. Only reason I had it there is because ArchWiki recommends it. So, fingers crossed, it'll be okay.

I hope I'm getting this right. If so, I will marked this thread as [SOLVED].
Thanks again.

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 25,266

Re: [SOLVED] iMac/Arch dual boot (systemd) reinstallation

Just for the general nitpick, systemd-boot and systemd are unrelated concepts. The former is a bootloader the latter an init system. But yes if you replace systemd with systemd-boot in all of these paragraphs then this will be the relevant "safe" end result.

godzillaknight

Member

Registered: 2022-07-19

Posts: 8

Re: [SOLVED] iMac/Arch dual boot (systemd) reinstallation

Thanks for the clarification.