virtualisation.fileSystems.<name>.overlay.upperdir
The path to the upperdir.
If this is null, a read-only overlay is created using the lowerdir.
If the filesystem is neededForBoot, this will be prefixed with /sysroot,
unless useStage1BaseDirectories is set to true.
If you set this to some value you MUST also set workdir.
- Type
null or string- Default
null- Declared
- <nixpkgs/nixos/modules/tasks/filesystems/overlayfs.nix>