| 22 May 2023 |
 Arian | (or maybe we do that already; idk) | 13:49:31 |
 @nikstur:matrix.org | In reply to @arianvp:matrix.org
shouldn't we be able to build an image without booting a VM? Afaik all the file systems that systemd-repart supports ("ext4", "btrfs", "xfs", "vfat", "erofs", "squashfs") can be created without a VM. In fact with this commit https://github.com/systemd/systemd/commit/1eb86ddde4f36165a99732b53cc97cef1acc3aa7 we can build disk images with systemd-repart in the nix build sandbox. For all but vfat and xfs the, mkfs tools take a directory and turn it into a fs. To build a vfat fs you need to copy the files manually (with mtools) into the fs image after you have created it (still in user space though) and for xfs there is a weird protofile which you can also create outside of a VM. I have no idea about the other filesystems NixOS supports. | 16:14:07 |
| @nikstur:matrix.org | And then there a fun things like bootctl install which checks that the ESP is a vfat fs, so afaik you cant call it in a chroot. | 16:14:37 |
 @elvishjerricco:matrix.org | How does repart's CopyFiles thing even work? | 16:16:08 |
| @nikstur:matrix.org | Ahh this is new, there is a variable for bootctl which disables the check $SYSTEMD_RELAX_ESP_CHECKS=1 | 16:16:29 |
| @nikstur:matrix.org | In reply to @elvishjerricco:matrix.org
How does repart's CopyFiles thing even work? It creates a root directory for most filesystems and then calls mkfs pointing at the root directory. | 16:17:11 |
| @elvishjerricco:matrix.org | well but how does it actually populate the file system with contents? | 16:17:27 |
| @elvishjerricco:matrix.org | does it mount the fs? | 16:17:34 |
| @elvishjerricco:matrix.org | or does it have some userspace way to write to the fs | 16:17:50 |
| @nikstur:matrix.org | mkfs does the population | 16:17:57 |
| @nikstur:matrix.org | See: https://github.com/systemd/systemd/blob/main/src/shared/mkfs-util.c#LL482C36-L482C36 | 16:18:00 |
| @nikstur:matrix.org | With the exception of vfat where they do something similar to what we do in our iso images: https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/installer/cd-dvd/iso-image.nix#L437 | 16:20:08 |
| @nikstur:matrix.org | And XFS which I don't really understand | 16:20:22 |
| @elvishjerricco:matrix.org | TIL it's common for mkfs.* to support prepopulation | 16:26:12 |
| Arian | So then we can get rid of qemu no? | 16:28:59 |
| @elvishjerricco:matrix.org | I doubt it? I think the thing qemu is for is so we can just run a regular install process. We don't have a static fs tree to populate with | 16:30:01 |
| @nikstur:matrix.org | Maybe make-diks-image-ng.nix for most use-cases? | 16:30:17 |
| Arian | But the FS tree is just a nix store closure no? | 16:30:31 |
| @nikstur:matrix.org | * Maybe make-diks-image-ng.nix for ~~most~~ a few use-cases? | 16:30:33 |
| Arian | /Etc gets populated in boot | 16:30:46 |
| @elvishjerricco:matrix.org | Arian: from make-disk-image.nix:
The Nix-store only image only need to run LKL tools to produce an image and will never spawn a virtual machine, whereas full images will always require a virtual machine, b
ut also use LKL.
| 16:31:13 |
| Arian | What else is there to populate except for some directories? | 16:31:17 |
| @elvishjerricco:matrix.org | so we already don't need a vm if we're just making a nix store image | 16:31:27 |
| @elvishjerricco:matrix.org | * Arian: from make-disk-image.nix:
The Nix-store only image only need to run LKL tools to produce an image and will never spawn a virtual machine, whereas full images will always require a virtual machine, but also use LKL.
| 16:31:40 |
| @elvishjerricco:matrix.org | Arian: A big part of what the VM is used for is useBootLoader | 16:32:30 |
| @elvishjerricco:matrix.org | because you actually have to do a boot loader install process | 16:32:40 |
| Arian | For EFI that's just files on the ESP | 16:33:01 |
| @nikstur:matrix.org | I have built disk images like that, but it might be hard to make all the installer tools behave | 16:33:42 |
| @nikstur:matrix.org | And then there are fun things like useSecureBoot where sd-boot populates efi-vars | 16:34:09 |
| @nikstur:matrix.org | * And then there are fun things like useSecureBoot where bootctl populates efi-vars | 16:34:28 |
