[wip] Add declarative unmount

cli.nix

@@ -23,6 +23,7 @@ let
           destroy = "_cliDestroyNoDeps";
           format = "_cliFormatNoDeps";
           mount = "_cliMountNoDeps";
+          unmount = "_cliUnmountNoDeps";
 
           "format,mount" = "_cliFormatMountNoDeps";
           "destroy,format,mount" = "_cliDestroyFormatMountNoDeps";
@@ -32,6 +33,7 @@ let
           destroy = "destroyNoDeps";
           format = "formatNoDeps";
           mount = "mountNoDeps";
+          unmount = "unmountNoDeps";
 
           "format,mount" = "formatMountNoDeps";
           "destroy,format,mount" = "destroyFormatMountNoDeps";
@@ -47,6 +49,7 @@ let
           destroy = "_cliDestroy";
           format = "_cliFormat";
           mount = "_cliMount";
+          unmount = "_cliUnmount";
 
           "format,mount" = "_cliFormatMount";
           "destroy,format,mount" = "_cliDestroyFormatMount";
@@ -55,7 +58,8 @@ let
         {
           destroy = "destroy";
           format = "format";
-          mount = "munt";
+          mount = "mount";
+          unmount = "unmount";
 
           "format,mount" = "formatMount";
           "destroy,format,mount" = "destroyFormatMount";

default.nix

@@ -31,6 +31,9 @@ in
   _cliMount = cfg: pkgs: ((eval cfg).config.disko.devices._scripts { inherit pkgs checked; }).mount;
   _cliMountNoDeps = cfg: pkgs: ((eval cfg).config.disko.devices._scripts { inherit pkgs checked; }).mountNoDeps;
 
+  _cliUnmount = cfg: pkgs: ((eval cfg).config.disko.devices._scripts { inherit pkgs checked; }).unmount;
+  _cliUnmountNoDeps = cfg: pkgs: ((eval cfg).config.disko.devices._scripts { inherit pkgs checked; }).unmountNoDeps;
+
   _cliFormatMount = cfg: pkgs: ((eval cfg).config.disko.devices._scripts { inherit pkgs checked; }).formatMount;
   _cliFormatMountNoDeps = cfg: pkgs: ((eval cfg).config.disko.devices._scripts { inherit pkgs checked; }).formatMountNoDeps;
 

disko

@@ -26,7 +26,7 @@ or else from the disko module of a NixOS configuration of that name under .nixos
 Options:
 
 * -m, --mode mode
-  set the mode, either distroy, format, mount, format,mount or destroy,format,mount
+  set the mode, either distroy, format, mount, unmount, format,mount or destroy,format,mount
     destroy: unmount filesystems and destroy partition tables of the selected disks
     format: create partition tables, zpools, lvms, raids and filesystems if they don't exist yet
     mount: mount the partitions at the specified root-mountpoint
@@ -136,7 +136,7 @@ nixBuild() {
 
 if ! {
   # Base modes
-  [[ $mode = "destroy" ]] || [[ $mode = "format" ]] || [[ $mode = "mount" ]] ||
+  [[ $mode = "destroy" ]] || [[ $mode = "format" ]] || [[ $mode = "mount" ]] || [[ $mode = "unmount" ]] ||
   # Combined modes
   [[ $mode = "format,mount" ]] ||
   [[ $mode = "destroy,format,mount" ]] || # Replaces --mode disko

disko-install

@@ -20,6 +20,8 @@ Usage: $0 [OPTIONS]
                               Specify this option if you plan to boot from this disk on the current machine,
                               but not if you plan to move the disk to another machine.
   --system-config JSON        Merges the specified JSON object into the NixOS configuration.
+  --mount-point PATH          Specify the mount point for the NixOS installation.
+                              Default: /mnt/disko-install-root
 EOF
 }
 
@@ -46,6 +48,7 @@ dry_run=
 extraSystemConfig="{}"
 diskoAttr=diskoScript
 writeEfiBootEntries=false
+mountPoint=/mnt/disko-install-root
 declare -A diskMappings
 declare -A extraFiles
 
@@ -135,6 +138,14 @@ parseArgs() {
       shift
       shift
       ;;
+    --mount-point)
+      if [[ $# -lt 2 ]]; then
+        echo "Option $1 requires an argument" >&2
+        exit 1
+      fi
+      mountPoint=$2
+      shift
+      ;;
     *)
       echo "Unknown option: $1" >&2
       showUsage
@@ -146,7 +157,6 @@ parseArgs() {
 }
 
 cleanupMountPoint() {
-  mountPoint=$1
   if mountpoint -q "${mountPoint}"; then
     umount -R "${mountPoint}"
   fi
@@ -161,6 +171,14 @@ nixBuild() {
   fi
 }
 
+maybeRun () {
+  if [[ -z ${dry_run-} ]]; then
+    "$@"
+  else
+    echo "Would run: $*"
+  fi
+}
+
 main() {
   parseArgs "$@"
 
@@ -170,7 +188,7 @@ main() {
   fi
 
   # check if we are root
-  if [[ "$EUID" -ne 0 ]]; then
+  if [[ "$EUID" -ne 0 ]] && [[ -z ${dry_run-} ]]; then
     echo "This script must be run as root" >&2
     exit 1
   fi
@@ -190,12 +208,12 @@ main() {
     exit 1
   fi
 
-  mountPoint="/mnt/disko-install-root"
-  mkdir -p "${mountPoint}"
-  chmod 755 "${mountPoint}" # bcachefs wants 755
-  escapeMountPoint=$(printf '%q' "$mountPoint")
+  maybeRun mkdir -p "${mountPoint}"
+  maybeRun chmod 755 "${mountPoint}" # bcachefs wants 755
   # shellcheck disable=SC2064
-  trap "cleanupMountPoint ${escapeMountPoint}" EXIT
+  if [[ -z ${dry_run-} ]]; then
+     trap cleanupMountPoint EXIT
+  fi
 
   outputs=$(nixBuild "${libexec_dir}"/install-cli.nix \
     "${nix_args[@]}" \
@@ -222,6 +240,9 @@ main() {
     exit 0
   fi
 
+  # We don't want swap as can break your running system in weird ways if you eject the disk
+  # Hopefully disko-install has enough RAM to run without swap, otherwise we can make this configurable in future.
+  export DISKO_SKIP_SWAP=1
   "$disko_script"
 
   for source in "${!extraFiles[@]}"; do

lib/default.nix

@@ -242,6 +242,8 @@ let
           postCreateHook = diskoLib.mkHook "shell commands to run after create";
           preMountHook = diskoLib.mkHook "shell commands to run before mount";
           postMountHook = diskoLib.mkHook "shell commands to run after mount";
+          preUnmountHook = diskoLib.mkHook "shell commands to run before unmount";
+          postUnmountHook = diskoLib.mkHook "shell commands to run after unmount";
         };
         config._module.args = {
           inherit diskoLib rootMountPoint;
@@ -284,6 +286,25 @@ let
         description = "Mount script";
       };
 
+    mkUnmountOption = { config, options, default }@attrs:
+      lib.mkOption {
+        internal = true;
+        readOnly = true;
+        type = diskoLib.jsonType;
+        default = lib.mapAttrsRecursive
+          (_name: value:
+            if builtins.isString value then ''
+              (
+                ${diskoLib.indent (diskoLib.defineHookVariables { inherit options; })}
+                ${diskoLib.indent config.preUnmountHook}
+                ${diskoLib.indent value}
+                ${diskoLib.indent config.postUnmountHook}
+              )
+            '' else value)
+          attrs.default;
+        description = "Unmount script";
+      };
+
     /* Writer for optionally checking bash scripts before writing them to the store
 
        writeCheckedBash :: AttrSet -> str -> str -> derivation
@@ -458,6 +479,10 @@ let
                   export PATH=${lib.makeBinPath (cfg.config._packages pkgs)}:$PATH
                   ${cfg.config._mount}
                 '';
+                unmount = (diskoLib.writeCheckedBash { inherit pkgs checked; }) "/bin/disko-unmount" ''
+                  export PATH=${lib.makeBinPath (cfg.config._packages pkgs)}:$PATH
+                  ${cfg.config._unmount}
+                '';
                 formatMount = (diskoLib.writeCheckedBash { inherit pkgs checked; }) "/bin/disko-format-mount" ''
                   export PATH=${lib.makeBinPath ((cfg.config._packages pkgs) ++ [ pkgs.bash ])}:$PATH
                   ${cfg.config._formatMount}
@@ -477,6 +502,9 @@ let
                 mountNoDeps = (diskoLib.writeCheckedBash { inherit pkgs checked; noDeps = true; }) "/bin/disko-mount" ''
                   ${cfg.config._mount}
                 '';
+                unmountNoDeps = (diskoLib.writeCheckedBash { inherit pkgs checked; noDeps = true; }) "/bin/disko-unmount" ''
+                  ${cfg.config._unmount}
+                '';
                 formatMountNoDeps = (diskoLib.writeCheckedBash { inherit pkgs checked; noDeps = true; }) "/bin/disko-format-mount" ''
                   ${cfg.config._formatMount}
                 '';
@@ -616,12 +644,32 @@ let
               ''
                 set -efux
                 # first create the necessary devices
-                ${concatMapStrings (dev: (attrByPath (dev ++ [ "_mount" ]) {} devices).dev or "") sortedDeviceList}
+                ${concatMapStrings (dev: (attrByPath (dev ++ [ "_mount" ]) {} devices).dev or "") (lib.reverseList sortedDeviceList)}
 
                 # and then mount the filesystems in alphabetical order
                 ${concatStrings (attrValues fsMounts)}
               '';
           };
+          _unmount = lib.mkOption {
+            internal = true;
+            type = lib.types.str;
+            description = ''
+              The script to unmount all devices defined by disko.devices
+            '';
+            default =
+              with lib; let
+                fsMounts = diskoLib.deepMergeMap (dev: dev._unmount.fs or { }) (flatten (map attrValues (attrValues devices)));
+                sortedDeviceList = diskoLib.sortDevicesByDependencies (cfg.config._meta.deviceDependencies or { }) devices;
+              in
+              ''
+                set -efux
+                # first unmount the filesystems in reverse alphabetical order
+                ${concatStrings (attrValues (lib.reverseList fsMounts))}
+
+                # Than close the devices
+                ${concatMapStrings (dev: (attrByPath (dev ++ [ "_unmount" ]) {} devices).dev or "") (lib.reverseList sortedDeviceList)}
+              '';
+          };
           _disko = lib.mkOption {
             internal = true;
             type = lib.types.str;

lib/tests.nix

@@ -99,6 +99,7 @@ let
         tsp-generator = pkgs.callPackage ../. { checked = true; };
         tsp-format = (tsp-generator._cliFormat testConfigInstall) pkgs;
         tsp-mount = (tsp-generator._cliMount testConfigInstall) pkgs;
+        tsp-unmount = (tsp-generator._cliUnmount testConfigInstall) pkgs;
         tsp-disko = (tsp-generator._cliDestroyFormatMount testConfigInstall) pkgs;
         tsp-config = tsp-generator.config testConfigBooted;
         num-disks = builtins.length (lib.attrNames testConfigBooted.disko.devices.disk);
@@ -282,6 +283,9 @@ let
             machine.succeed("${lib.getExe tsp-format}")
             machine.succeed("${lib.getExe tsp-mount}")
             machine.succeed("${lib.getExe tsp-mount}") # verify that mount is idempotent
+            machine.succeed("${lib.getExe tsp-unmount}")
+            machine.succeed("${lib.getExe tsp-unmount}") # verify that umount is idempotent
+            machine.succeed("${lib.getExe tsp-mount}") # verify that mount is idempotent
             machine.succeed("${lib.getExe tsp-disko} --yes-wipe-all-disks") # verify that we can destroy and recreate
             machine.succeed("mkdir -p /mnt/home")
             machine.succeed("touch /mnt/home/testfile")

lib/types/btrfs.nix

@@ -199,6 +199,34 @@ in
           };
         };
     };
+    _unmount = diskoLib.mkUnmountOption {
+      inherit config options;
+      default =
+        let
+          subvolMounts = lib.concatMapAttrs
+            (_: subvol:
+              lib.optionalAttrs
+              (subvol.mountpoint != null)
+              {
+                ${subvol.mountpoint} = ''
+                  if findmnt "${config.device}" "${rootMountPoint}${subvol.mountpoint}" > /dev/null 2>&1; then
+                    umount "${rootMountPoint}${subvol.mountpoint}"
+                  fi
+                '';
+              }
+            )
+            config.subvolumes;
+        in
+        {
+          fs = subvolMounts // lib.optionalAttrs (config.mountpoint != null) {
+            ${config.mountpoint} = ''
+              if findmnt "${config.device}" "${rootMountPoint}${config.mountpoint}" > /dev/null 2>&1; then
+                umount "${rootMountPoint}${config.mountpoint}"
+              fi
+            '';
+          };
+        };
+    };
     _config = lib.mkOption {
       internal = true;
       readOnly = true;

lib/types/disk.nix

@@ -49,6 +49,10 @@
       inherit config options;
       default = lib.optionalAttrs (config.content != null) config.content._mount;
     };
+    _unmount = diskoLib.mkUnmountOption {
+      inherit config options;
+      default = lib.optionalAttrs (config.content != null) config.content._mount;
+    };
     _config = lib.mkOption {
       internal = true;
       readOnly = true;

lib/types/filesystem.nix

@@ -64,6 +64,16 @@
         '';
       };
     };
+    _unmount = diskoLib.mkUnmountOption {
+      inherit config options;
+      default = lib.optionalAttrs (config.mountpoint != null) {
+        fs.${config.mountpoint} = ''
+          if findmnt "${config.device}" "${rootMountPoint}${config.mountpoint}" >/dev/null 2>&1; then
+            umount "${rootMountPoint}${config.mountpoint}"
+          fi
+        '';
+      };
+    };
     _config = lib.mkOption {
       internal = true;
       readOnly = true;

lib/types/gpt.nix

@@ -249,6 +249,14 @@ in
           fs = partMounts.fs or { };
         };
     };
+    _unmount = diskoLib.mkUnmountOption {
+      inherit config options;
+      default = ''
+        ${lib.concatStrings (map (partition: ''
+          ${lib.optionalString (partition.content != null) partition.content._unmount}
+        '') sortedPartitions)}
+      '';
+    };
     _config = lib.mkOption {
       internal = true;
       readOnly = true;

lib/types/luks.nix

@@ -170,6 +170,16 @@ in
           fs = lib.optionalAttrs (config.content != null) contentMount.fs or { };
         };
     };
+    _unmount = diskoLib.mkUnmountOption {
+      inherit config options;
+      default = ''
+        ${lib.optionalString (config.content != null) config.content._unmount}
+
+        if cryptsetup status "${config.name}" >/dev/null 2>/dev/null; then
+          cryptsetup close "${config.name}"
+        fi
+      '';
+    };
     _config = lib.mkOption {
       internal = true;
       readOnly = true;

lib/types/lvm_pv.nix

@@ -41,6 +41,10 @@
       inherit config options;
       default = { };
     };
+    _unmount = diskoLib.mkUnmountOption {
+      inherit config options;
+      default = { };
+    };
     _config = lib.mkOption {
       internal = true;
       readOnly = true;

lib/types/lvm_vg.nix

@@ -127,6 +127,20 @@ in
           fs = lvMounts.fs or { };
         };
     };
+    _unmount = diskoLib.mkUnmountOption {
+      inherit config options;
+      default =
+        let
+          lvMounts = diskoLib.deepMergeMap
+            (lv:
+              lib.optionalAttrs (lv.content != null) lv.content._unmount
+            )
+            (lib.attrValues config.lvs);
+        in
+        ''
+          ${lib.concatMapStrings (x: x.dev or "") (lib.attrValues lvMounts)}
+        '';
+    };
     _config = lib.mkOption {
       internal = true;
       readOnly = true;