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Diffstat (limited to 'shared')
| -rw-r--r-- | shared/nixos/zfs-impermenance/default.nix | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/shared/nixos/zfs-impermenance/default.nix b/shared/nixos/zfs-impermenance/default.nix new file mode 100644 index 0000000..f1789a6 --- /dev/null +++ b/shared/nixos/zfs-impermenance/default.nix @@ -0,0 +1,32 @@ +# This module sets up basic impermenance the way I like to do it on my ZFS +# hosts. It assumes there is a main zpool called rpool, which has a dataset +# `rpool/local/root` mounted at `/`, and that the dataset has an empty dataset +# called `@blank`. +# +# Here is the dataset structure I use: +# +# rpool +# ├── local +# │ ├── nix (atime=off, mountpoint=/nix) +# │ └── root (mountpoint=/) +# └── safe +# ├── home (mountpoint=/home) +# └── persist (mountpoint=/persist) +# +# I usually follow the convention that `rpool/local` isn't backed up and +# `rpool/safe` is. +# +# See: https://grahamc.com/blog/erase-your-darlings/ +{lib, ...}: { + # Reset / to empty on boot. This is what achieves the impermenance. + # Unlike the holy book (the linked article), I had to use `postResumeCommands` + # as this is the step where ZFS imports the dataset (but doesnt't mounted it yet). + # See: https://github.com/NixOS/nixpkgs/blob/b681065d0919f7eb5309a93cea2cfa84dec9aa88/nixos/modules/tasks/filesystems/zfs.nix#L627-L659 + boot.initrd.postResumeCommands = lib.mkAfter '' + zfs rollback -r rpool/local/root@blank + ''; + + # Filesystems with mountpoints at `/` and `/nix` are automatically mounted at boot, + # but `/persist` is bespoke, so we have to teach init about that one ourselves. + fileSystems."/persist".neededForBoot = true; +} |