| 10 Nov 2022 |
 @elvishjerricco:matrix.org | wait so your root is on a btrfs mirror and you removed one disk? | 18:27:29 |
| @elvishjerricco:matrix.org | Does that work on the old initrd? | 18:27:42 |
 @me:linj.tech | In reply to @elvishjerricco:matrix.org
Does that work on the old initrd? no, the old initrd just dies if one disk is missing. Because of that, I try this systemd one | 18:28:35 |
| @elvishjerricco:matrix.org | Ah, yea I wouldn't really expect that to be supported. I was actually looking into this a bit yesterday and the btrfs udev rules shipped with systemd deliberately don't mark the disks as active until all of them are present | 18:29:25 |
| @elvishjerricco:matrix.org | and | 18:29:37 |
| @elvishjerricco:matrix.org | even if you're not using udev/systemd, the btrfs tools by default don't let you mount degraded | 18:29:56 |
| @me:linj.tech | In reply to @elvishjerricco:matrix.org
even if you're not using udev/systemd, the btrfs tools by default don't let you mount degraded degraded can be set I think | 18:30:38 |
| @elvishjerricco:matrix.org | yea it has to be a mount option | 18:30:45 |
| @elvishjerricco:matrix.org | but that doesn't affect the udev rule | 18:30:59 |
| @elvishjerricco:matrix.org | I think I see how this works:
https://github.com/systemd/systemd/blob/main/rules.d/64-btrfs.rules.in
Basically there's a udev builtin btrfs ready that checks if a device is ready to be used as a btrfs FS; i.e. if all its partner disks are present. If not, it sets SYSTEMD_READY=0 so that it doesn't activate the .device unit. Once one of them says its ready, it allows SYSTEMD_READY to remain 1, then triggers the others to check again. This will (presumably) cause all the others to check and set SYSTEMD_READY=1. Now if any of those devices is the device unit for your mount unit, the mount unit can now activate
| 18:31:16 |
| @elvishjerricco:matrix.org | ^ That's the message forwarded from what I found yesterday | 18:31:30 |
| @elvishjerricco:matrix.org | So the rule basically says "no device is available until all are" | 18:32:28 |
| @elvishjerricco:matrix.org | dunno if we include that rule in systemd-stage-1 or not | 18:32:43 |
| @elvishjerricco:matrix.org | I think we do? | 18:32:45 |
| @elvishjerricco:matrix.org | Looks like we do | 18:36:11 |
| @me:linj.tech | thanks for the info. | 18:36:28 |
| @elvishjerricco:matrix.org | In reply to @me:linj.tech
no, the old initrd just dies if one disk is missing. Because of that, I try this systemd one I'd be curious what it looks like when the scripted initrd dies this way | 18:39:04 |
| @me:linj.tech | kernel panic | 18:39:29 |
| @elvishjerricco:matrix.org | linj: O_O | 18:39:39 |
| @me:linj.tech | I can take a screenshot if you want | 18:39:46 |
| @elvishjerricco:matrix.org | that would be wonderful | 18:39:52 |
| @me:linj.tech | 
Download image.png | 18:41:19 |
| @elvishjerricco:matrix.org | I see | 18:41:50 |
| @elvishjerricco:matrix.org | It dies because it doesn't find luks-2 at all | 18:41:56 |
| @me:linj.tech | the old initrd is easy to workaround for this case | 18:41:57 |
| @elvishjerricco:matrix.org | so | 18:42:19 |
| @elvishjerricco:matrix.org | once you're in the emergency shell in the systemd stage 1, you can probably manually mount the degraded btrfs root and let it continue with systemctl default | 18:42:44 |
| @me:linj.tech | https://github.com/NixOS/nixpkgs/blob/717ccacc16e8de01ff06f2f83db6415c01f11527/nixos/modules/system/boot/luksroot.nix#L155 | 18:42:44 |
| @me:linj.tech | just do not die and skip some functions | 18:42:57 |
| @elvishjerricco:matrix.org | linj: Btw what does your fileSystems."/".device look like? | 18:45:20 |
