{ fileSystems = { "/" = { device = "tmpfs"; fsType = "tmpfs"; options = ["size=4G" "mode=755"]; }; "/boot" = { device = "/dev/disk/by-label/BOOT"; fsType = "vfat"; }; "/home".neededForBoot = true; "/nix" = { fsType = "btrfs"; options = ["subvol=nix" "compress=zstd" "noatime"]; }; "/persist" = { fsType = "btrfs"; options = ["subvol=persist" "compress=zstd" "noatime"]; neededForBoot = true; }; "/tmp" = { device = "tmpfs"; fsType = "tmpfs"; options = ["size=8G" "mode=777"]; }; "/var/log" = { fsType = "btrfs"; options = ["subvol=log" "compress=zstd" "noatime"]; neededForBoot = true; }; }; environment.persistence."/persist" = { directories = ["/var/lib" "/var/cache"]; files = ["/etc/machine-id"]; }; }