Storage
Filesystems at a glance
| FS | Use in this flake | Best for |
|---|---|---|
| ext4 | the default root filesystem for most hosts | Simplicity, zero maintenance |
| btrfs | root on shinji, yhwach, kyuubi | Compression, snapshots |
| zfs | data pools only (sado, kuchiki) | Large storage, checksums |
| vfat | Every host with /boot (EFI) | EFI system partition |
Host → filesystem mapping
| Host | Root | Data | Managed by |
|---|---|---|---|
| shinji | btrfs (@root + @nix) | — | disko |
| yhwach | btrfs (subvol=@) | — | hardware-config |
| kyuubi | btrfs (subvol=@) | — | hardware-config |
| sado | ext4 | zfs (/mnt/flash) | hardware-config |
| kuchiki | ext4 | zfs (/mnt/storage) | hardware-config |
| kenpachi | ext4 (LVM) | — | disko |
| aizen | ext4 (LVM) | — | disko |
| all others | ext4 | — | hardware-config |
Choosing a filesystem for a new host
- ext4 — the default. Simple, proven, zero configuration. Used on most hosts.
- btrfs — when you want transparent zstd compression (saves ~25% on
/nix/store) or snapshot support. Use the@root+@nixsubvolume layout to keep snapshots lightweight. See btrfs.md for details. - zfs — only for dedicated data pools that benefit from checksums, dedup, or RAID-Z. Do not use for root: the out-of-tree kernel module frequently breaks on kernel updates.
Disko
Disko provides declarative disk partitioning. Instead of manually running fdisk, mkfs, and recording UUIDs in hardware-configuration.nix, you define everything in a disk.nix:
- Partition layout (BIOS boot, ESP, root)
- Filesystem type (ext4, btrfs, zfs)
- Subvolume layout for btrfs
- LVM volumes if needed
Disko is imported per-host via inputs.disko.nixosModules.disko in the host’s disk.nix. A few hosts use it (shinji, kenpachi, aizen); the rest use a manually-generated hardware-configuration.nix with explicit fileSystems entries.
When disko manages the filesystems, the fileSystems entries in hardware-configuration.nix should be commented out — disko generates them declaratively at build time.
Example: shinji
# systems/x86_64-linux/shinji/default.nix
{ inputs, ... }: {
imports = [
./configuration.nix
./disk.nix # disko: btrfs on NVMe with @root + @nix subvolumes
./hardware-configuration.nix # fileSystems commented out, disko handles them
];
}
See btrfs.md for a complete disko + btrfs walkthrough.