various small fixes, fixes + fileSystems.*.postUnmountCommands

lib/setup-scripts/add-key.sh

@@ -28,7 +28,8 @@ function gen-key-usb-part {( set -eu # 1: usage
 
 ## Outputs a key by simply printing an different keystore entry (that must have been generated before).
 function gen-key-copy {( set -eu # 1: _, 2: source
-    keystore=/run/keystore-@{config.networking.hostName!hashString.sha256:0:8} ; source=$2
+    source=$2
+    keystore=/run/keystore-@{config.networking.hostName!hashString.sha256:0:8}
     cat "$keystore"/"$source".key
 )}
 
@@ -41,16 +42,17 @@ function gen-key-constant {( set -eu # 1: _, 2: value
 ## Obtains a key by prompting for a password.
 function gen-key-password {( set -eu # 1: usage
     usage=$1
-    ( prompt-new-password "as key for @{config.networking.hostName}:$usage" || \exit 1 )
+    ( prompt-new-password "as key »(@{config.networking.hostName}:)$usage«" || \exit 1 )
 )}
 
 ## Generates a key by prompting for (or reusing) a »$user«'s password, combining it with »$keystore/home/$user.key«.
 function gen-key-home-composite {( set -eu # 1: usage, 2: user
-    keystore=/run/keystore-@{config.networking.hostName!hashString.sha256:0:8} ; usage=$1 ; user=$2
+    usage=$1 ; user=$2
+    keystore=/run/keystore-@{config.networking.hostName!hashString.sha256:0:8}
     if [[ ${!userPasswords[@]} && ${userPasswords[$user]:-} ]] ; then
         password=${userPasswords[$user]}
     else
-        password=$(prompt-new-password "that will be used as component of the key for »@{config.networking.hostName}:$usage«")
+        password=$(prompt-new-password "for the user account »$user« (as component for key »(@{config.networking.hostName}:)$usage«)")
         if [[ ! $password ]] ; then \exit 1 ; fi
     fi
     { cat "$keystore"/home/"$user".key && cat <<<"$password" ; } | sha256sum | head -c 64
@@ -60,49 +62,49 @@ function gen-key-home-composite {( set -eu # 1: usage, 2: user
 function gen-key-home-yubikey {( set -eu # 1: usage, 2: serialAndSlotAndUser(as »serial:slot:user«)
     usage=$1 ; args=$2
     serial=$( <<<"$args" cut -d: -f1 ) ; slot=$( <<<"$args" cut -d: -f2 )
-    user=${args/$serial:$slot:/}
+    user=${args#$serial:$slot:}
     if [[ ${!userPasswords[@]} && ${userPasswords[$user]:-} ]] ; then
         password=${userPasswords[$user]}
     else
-        password=$(prompt-new-password "as YubiKey challenge for »@{config.networking.hostName}:$usage«")
+        password=$(prompt-new-password "for the user account »$user« (as YubiKey challenge for key »:$usage«)")
         if [[ ! $password ]] ; then \exit 1 ; fi
     fi
-    gen-key-yubikey-challenge "$usage" "$serial:$slot:home-$user=$password" true "»${user}«'s password (for key »${usage}«)"
+    gen-key-yubikey-challenge "$usage" "$serial:$slot:home-$user=$password" true "»${user}«'s password (to create key »:${usage}«)"
 )}
 
 ## Generates a reproducible secret by prompting for a pin/password and then challenging slot »$slot« of YubiKey »$serial«.
 function gen-key-yubikey-pin {( set -eu # 1: usage, 2: serialAndSlot(as »serial:slot«)
     usage=$1 ; serialAndSlot=$2
-    pin=$( prompt-new-password "/ pin as challenge to YubiKey »$serialAndSlot« as key for »@{config.networking.hostName}:$usage«" )
+    pin=$( prompt-new-password "/ pin as challenge to YubiKey »$serialAndSlot« for key »:$usage«" )
     if [[ ! $pin ]] ; then \exit 1 ; fi
-    gen-key-yubikey-challenge "$usage" "$serialAndSlot:$pin" true "password / pin as key for »@{config.networking.hostName}:$usage«"
+    gen-key-yubikey-challenge "$usage" "$serialAndSlot:$pin" true "password / pin to create key »:$usage«"
 )}
 
-## Generates a reproducible secret for a certain »$use«case and optionally »$salt« on a »$host« by challenging slot »$slot« of YubiKey »$serial«.
+## Generates a reproducible secret for a certain »$use«case and optionally »$salt« specific to the current host(name) by challenging slot »$slot« of YubiKey »$serial«.
 function gen-key-yubikey {( set -eu # 1: usage, 2: serialAndSlotAndSalt(as »serial:slot:salt«)
     usage=$1 ; args=$2
     serial=$( <<<"$args" cut -d: -f1 ) ; slot=$( <<<"$args" cut -d: -f2 )
     salt=${args/$serial:$slot:/}
     usagE="$usage" ; if [[ "$usage" =~ ^(luks/.*/[0-8])$ ]] ; then usagE="${usage:0:(-2)}" ; fi # produce the same secret, regardless of the target luks slot
     challenge="@{config.networking.hostName}:$usagE${salt:+:$salt}"
-    gen-key-yubikey-challenge "$usage" "$serial:$slot:$challenge"
+    gen-key-yubikey-challenge "$usage" "$serial:$slot:$challenge" '' "challenge »"$challenge":1/2« to create key »@{config.networking.hostName}:$usage«"
 )}
 
 ## Generates a reproducible secret by challenging slot »$slot« of YubiKey »$serial« with the fixed »$challenge«.
 function gen-key-yubikey-challenge {( set -eu # 1: _, 2: serialAndSlotAndChallenge(as »$serial:$slot:$challenge«), 3?: onlyOnce, 4?: message
-    args=$2 ; message=${4:-}
+    args=$2 ; onlyOnce=$3 ; message=$4
     serial=$( <<<"$args" cut -d: -f1 ) ; slot=$( <<<"$args" cut -d: -f2 )
     challenge=${args/$serial:$slot:/}
 
     if [[ "$serial" != "$( @{native.yubikey-personalization}/bin/ykinfo -sq 2>/dev/null )" ]] ; then printf 'Please insert / change to YubiKey with serial %s!\n' "$serial" 1>&2 ; fi
-    if [[ ! "${3:-}" ]] ; then
+    if [[ ! $onlyOnce ]] ; then
-        read -p 'Challenging YubiKey '"$serial"' slot '"$slot"' twice with '"${message:-challenge »"$challenge":1/2«}"'. Enter to continue, or Ctrl+C to abort:'
+        read -p 'Challenging YubiKey '"$serial"' slot '"$slot"' twice with '"$message"'. Enter to continue, or Ctrl+C to abort:'
     else
-        read -p 'Challenging YubiKey '"$serial"' slot '"$slot"' once with '"${message:-challenge »"$challenge"«}"'. Enter to continue, or Ctrl+C to abort:'
+        read -p 'Challenging YubiKey '"$serial"' slot '"$slot"' once with '"$message"'. Enter to continue, or Ctrl+C to abort:'
     fi
     if [[ "$serial" != "$( @{native.yubikey-personalization}/bin/ykinfo -sq )" ]] ; then printf 'YubiKey with serial %s not present, aborting.\n' "$serial" 1>&2 ; \exit 1 ; fi
 
-    if [[ ! "${3:-}" ]] ; then
+    if [[ ! $onlyOnce ]] ; then
         secret="$( @{native.yubikey-personalization}/bin/ykchalresp -"$slot" "$challenge":1 )""$( sleep .5 || : ; @{native.yubikey-personalization}/bin/ykchalresp -"$slot" "$challenge":2 || @{native.yubikey-personalization}/bin/ykchalresp -"$slot" "$challenge":2 )" # the second consecutive challenge tends to fail if it follows immediately
         if [[ ${#secret} != 80 ]] ; then printf 'YubiKey challenge failed, aborting.\n' "$serial" 1>&2 ; \exit 1 ; fi
     else

lib/setup-scripts/disk.sh

@@ -9,7 +9,6 @@ declare-flag install-system skip-formatting "" "Skip partitioning, formatting, a
 function do-disk-setup { # 1: diskPaths
 
     ensure-disks "$1" || return
-    prompt-for-user-passwords || return
 
     export mnt=/tmp/nixos-install-@{config.networking.hostName} && mkdir -p "$mnt" && prepend_trap "rmdir $mnt" EXIT || return # »mnt=/run/user/0/...« would be more appropriate, but »nixos-install« does not like the »700« permissions on »/run/user/0«
 
@@ -22,6 +21,7 @@ function do-disk-setup { # 1: diskPaths
         open-luks-layers || return
         if [[ $(LC_ALL=C type -t import-zpools) == function ]] ; then import-zpools $mnt || return ; fi
     else
+        prompt-for-user-passwords || return
         populate-keystore || return
         partition-disks || return
         create-luks-layers || return
@@ -34,9 +34,9 @@ function do-disk-setup { # 1: diskPaths
         run-hook-script 'Post Formatting' @{config.installer.commands.postFormat!writeText.postFormatCommands} || return
     fi
 
-    fix-grub-install || return
+    #fix-grub-install || return
 
-    prepend_trap "unmount-system $mnt" EXIT && mount-system $mnt || return
+    prepend_trap "unmount-system $mnt" EXIT && mount-system $mnt '' "${args[skip-formatting]:-}" || return
     run-hook-script 'Post Mounting' @{config.installer.commands.postMount!writeText.postMountCommands} || return
 }
 
@@ -200,7 +200,7 @@ function format-partitions {
     for swapDev in "@{config.swapDevices!catAttrs.device[@]}" ; do
         if [[ $swapDev == /dev/disk/by-partlabel/* ]] ; then
             if ! is-partition-on-disks "$swapDev" "${blockDevs[@]}" ; then echo "Partition alias $swapDev used for SWAP does not point at one of the target disks ${blockDevs[@]}" 1>&2 ; \return 1 ; fi
-            @{native.util-linux}/bin/wipefs --all "${fs[device]}" >$beLoud 2>$beSilent || return # else mkswap might refuse to replace any previous filesystems
+            @{native.util-linux}/bin/wipefs --all "$swapDev" >$beLoud 2>$beSilent || return # else mkswap might refuse to replace any previous filesystems
         elif [[ $swapDev == /dev/mapper/* ]] ; then
             if [[ ! @{config.boot.initrd.luks.devices!catAttrSets.device[${swapDev/'/dev/mapper/'/}]:-} ]] ; then echo "LUKS device $swapDev used for SWAP does not point at one of the device mappings @{!config.boot.initrd.luks.devices!catAttrSets.device[@]}" 1>&2 ; \return 1 ; fi
         else continue ; fi
@@ -226,11 +226,11 @@ function fix-grub-install {
 }
 
 ## Mounts all file systems as it would happen during boot, but at path prefix »$mnt« (instead of »/«).
-function mount-system {( # 1: mnt, 2?: fstabPath, 3?: allowFail
+function mount-system {( # 1: mnt, 2?: fstabPath, 3?: allowNoautoFail
     # While not generally required for fstab, nixos uses the dependency-sorted »config.system.build.fileSystems« list (instead of plain »builtins.attrValues config.fileSystems«) to generate »/etc/fstab« (provided »config.fileSystems.*.depends« is set correctly, e.g. for overlay mounts).
     # This function depends on the file at »fstabPath« to be sorted like that.
 
-    mnt=$1 ; fstabPath=${2:-"@{config.system.build.toplevel}/etc/fstab"} ; allowFail=${3:-}
+    mnt=$1 ; fstabPath=${2:-"@{config.system.build.toplevel}/etc/fstab"} ; allowNoautoFail=${3:-}
     PATH=@{native.e2fsprogs}/bin:@{native.f2fs-tools}/bin:@{native.xfsprogs}/bin:@{native.dosfstools}/bin:$PATH
 
     # The following is roughly equivalent to: mount --all --fstab "$fstabPath" --target-prefix "$mnt" -o X-mount.mkdir # (but »--target-prefix« does not apply to bind/overlay sources)
@@ -239,7 +239,13 @@ function mount-system {( # 1: mnt, 2?: fstabPath, 3?: allowFail
         options=,$options, ; options=${options//,ro,/,}
 
         if ! @{native.util-linux}/bin/mountpoint -q "$mnt"/"$target" ; then (
-            mkdir-sticky "$mnt"/"$target" || exit
+
+            if [[ $options =~ ,x-bind-file, ]] ; then
+                mkdir-sticky "$(dirname "$mnt"/"$target")" && touch -a "$mnt"/"$target" || \exit
+            else
+                mkdir-sticky "$mnt"/"$target" || \exit
+            fi
+
             [[ $type == tmpfs || $type == auto || $type == */* ]] || @{native.kmod}/bin/modprobe --quiet $type || true # (this does help sometimes)
 
             if [[ $type == overlay ]] ; then
@@ -251,12 +257,18 @@ function mount-system {( # 1: mnt, 2?: fstabPath, 3?: allowFail
                 # TODO: test the lowerdir stuff
             elif [[ $options =~ ,r?bind, ]] ; then
                 if [[ $source == /nix/store/* ]] ; then options=,ro$options ; fi
-                source=$mnt/$source ; if [[ ! -e $source ]] ; then mkdir-sticky "$source" || exit ; fi
+                source=$mnt/$source ; if [[ ! -e $source ]] ; then
+                    if [[ $options =~ ,x-bind-file, ]] ; then
+                        mkdir-sticky "$(dirname "$source")" && touch -a "$source" || \exit
+                    else
+                        mkdir-sticky "$source" || \exit
+                    fi
+                fi
             fi
 
-            @{native.util-linux}/bin/mount -t $type -o "${options:1:(-1)}" "$source" "$mnt"/"$target" || exit
+            @{native.util-linux}/bin/mount -t $type -o "${options:1:(-1)}" "$source" "$mnt"/"$target" || \exit
 
-        ) || [[ $options == *,nofail,* || $allowFail ]] || exit ; fi # (actually, nofail already makes mount fail silently)
+        ) || [[ $options == *,nofail,* ]] || [[ $options == *,noauto,* && $allowNoautoFail ]] || exit ; fi # (actually, nofail already makes mount fail silently)
     done 3< <( <$fstabPath grep -v '^#' )
 )}
 

lib/setup-scripts/install.sh

@@ -62,7 +62,7 @@ function prepare-installer { # 1: diskPaths
         if @{native.zfs}/bin/zfs get -o value -H name "$poolName" &>/dev/null ; then echo "ZFS pool »$poolName« is already imported. Export the pool before running the installer." 1>&2 ; \return 1 ; fi
     done
 
-    if [[ ${SUDO_USER:-} && $( PATH=$hostPath which su 2>/dev/null ) ]] ; then # use Nix as the user who called this script, as Nix may not be set up for root
+    if [[ ${SUDO_USER:-} && ! $( PATH=$hostPath which nix 2>/dev/null ) && $( PATH=$hostPath which su 2>/dev/null ) ]] ; then # use Nix as the user who called this script, as Nix may not be set up for root
         function nix {( set +x ; declare -a args=("$@") ; PATH=$hostPath su - "$SUDO_USER" -s "@{native.bashInteractive!getExe}" -c "$(declare -p args)"' ; nix "${args[@]}"' )}
     else # use Nix by absolute path, as it won't be on »$PATH«
         PATH=$PATH:@{native.nix}/bin
@@ -73,6 +73,7 @@ function prepare-installer { # 1: diskPaths
 }
 
 declare-flag install-system vm-shared "dir-path" "When installing inside the VM, specifies a host path that is read-write mounted at »/tmp/shared« inside the VM."
+declare-flag install-system vm-args "qemu-args" "When installing inside the VM, extra arguments to pass to qemu."
 
 ## Re-executes the current system's installation in a qemu VM.
 function reexec-in-qemu {
@@ -110,7 +111,7 @@ function reexec-in-qemu {
 
     local runInVm ; runInVm=$( build-lazy $output )/bin/run-@{config.system.name}-vm-exec || return
 
-    $runInVm ${args[vm-shared]:+--shared="${args[vm-shared]}"} ${args[debug]:+--initrd-console} ${args[trace]:+--initrd-console} ${args[quiet]:+--quiet} -- "$command" "${qemu[@]}" || return # --initrd-console
+    $runInVm ${args[vm-shared]:+--shared="${args[vm-shared]}"} ${args[debug]:+--initrd-console} ${args[trace]:+--initrd-console} ${args[quiet]:+--quiet} -- "$command" "${qemu[@]}" ${args[vm-args]:-} || return # --initrd-console
 }
 
 
@@ -162,7 +163,7 @@ function install-system-to {( set -u # 1: mnt, 2?: topLevel
     fi
 
     # Copy system closure to new nix store:
-    if [[ ${SUDO_USER:-} ]] ; then chown -R $SUDO_USER: $mnt/nix/store $mnt/nix/var || exit ; fi
+    if declare -f nix >&/dev/null ; then chown -R $SUDO_USER: $mnt/nix/store $mnt/nix/var || exit ; fi
     cmd=( nix --extra-experimental-features nix-command --offline copy --no-check-sigs --to $mnt "$topLevel" )
     if [[ ${args[quiet]:-} ]] ; then
         "${cmd[@]}" --quiet >/dev/null 2> >( grep -Pe '^error:' || true ) || exit
@@ -173,7 +174,7 @@ function install-system-to {( set -u # 1: mnt, 2?: topLevel
     fi
     rm -rf $mnt/nix/var/nix/gcroots || exit
     # TODO: if the target has @{config.nix.settings.auto-optimise-store} and the host doesn't (there is no .links dir?), optimize now
-    if [[ ${SUDO_USER:-} ]] ; then chown -R root:root $mnt/nix $mnt/nix/var || exit ; chown :30000 $mnt/nix/store || exit ; fi
+    if declare -f nix >&/dev/null ; then chown -R root:root $mnt/nix $mnt/nix/var || exit ; chown :30000 $mnt/nix/store || exit ; fi
 
     # Set this as the initial system generation (in case »nixos-install-cmd« won't):
     # (does about the same as »nix-env --profile /nix/var/nix/profiles/system --set $targetSystem«)

lib/setup-scripts/keys.sh

@@ -6,7 +6,7 @@ function prompt-for-user-passwords { # (void)
     local user ; for user in "@{!config.users.users!catAttrSets.password[@]}" ; do # Also grab any plaintext passwords for testing setups.
         userPasswords[$user]=@{config.users.users!catAttrSets.password[$user]}
     done
-    local user ; for user in "@{!config.users.users!catAttrSets.passwordFile[@]}" ; do
+    local user ; for user in "@{!config.users.users!catAttrSets.hashedPasswordFile[@]}" "@{!config.users.users!catAttrSets.passwordFile[@]}" ; do
         for attempt in 2 3 x ; do
             if userPasswords[$user]=$(prompt-new-password "for the user account »$user«") ; then break ; fi
             if [[ $attempt == x ]] ; then \return 1 ; fi ; echo "Retrying ($attempt/3):"

lib/setup-scripts/maintenance.sh

@@ -212,6 +212,7 @@ function mount-keystore-luks-primary {
     local method=@{config.setup.keystore.keys[$usage]%%=*}
     local options=@{config.setup.keystore.keys[$usage]:$(( ${#method} + 1 ))}
 
+    echo 'Opening keystore with primary key (this may cause prompts, but no new keys are written):'
     local attempt ; for attempt in 2 3 x ; do
         if mount-keystore-luks --key-file=<( gen-key-"$method" "$usage" "$options" ) ; then break ; fi
         if [[ $attempt == x ]] ; then \return 1 ; fi ; echo "Retrying ($attempt/3):"

lib/setup-scripts/utils.sh

@@ -89,7 +89,7 @@ function build-lazy { # 1: drvPath, 2?: output
 }
 
 ## Tests whether (returns 0/success if) the first version argument is greater/less than (or equal) the second version argument.
-function version-gr-eq { printf '%s\n%s' "$1" "$2" | sort -C -V -r ; }
+function version-gr-eq { printf '%s\n%s' "$1" "$2" | LC_ALL=C sort -C -V -r ; }
-function version-lt-eq { printf '%s\n%s' "$1" "$2" | sort -C -V ; }
+function version-lt-eq { printf '%s\n%s' "$1" "$2" | LC_ALL=C sort -C -V ; }
 function version-gt { ! version-gt-eq "$2" "$1" ; }
 function version-lt { ! version-lt-eq "$2" "$1" ; }

lib/setup-scripts/zfs.sh

@@ -25,6 +25,8 @@ Creates a single of the system's ZFS pools, and its datasets. Can be called manu
 EOD
 declare-flag install-system,create-zpool zpool-force "" "When creating ZFS storage pools, pass the »-f« (force) option. This may be required when installing to disks that are currently part of a pool, or ZFS refuses do reuse them."
 function create-zpool {
+    local beLoud=/dev/null ; if [[ ${args[debug]:-} ]] ; then beLoud=/dev/stdout ; fi
+    local beSilent=/dev/stderr ; if [[ ${args[quiet]:-} ]] ; then beSilent=/dev/null ; fi
     local mnt=$1 ; local poolName=$2
     eval 'local -A pool='"@{config.setup.zfs.pools[$poolName]}"
     eval 'local -a vdevs='"${pool[vdevArgs]}"
@@ -45,6 +47,7 @@ function create-zpool {
         else
             part=/dev/disk/by-partlabel/$part ; vdevs[$index]=$part
             if ! is-partition-on-disks "$part" "${blockDevs[@]}" ; then echo "Partition alias $part used by zpool ${pool[name]} does not point at one of the target disks ${blockDevs[@]}" 1>&2 ; \return 1 ; fi
+            @{native.util-linux}/bin/wipefs --all "$part" >$beLoud 2>$beSilent || return # else mkfs might refuse to replace any previous filesystems
         fi
     done
     @{native.kmod}/bin/modprobe zfs || true
@@ -147,6 +150,7 @@ function ensure-datasets {
             ( PATH=@{native.zfs}/bin ; ${_set_x:-:} ; zfs allow -$who "${allows[$who]}" "${dataset[name]}" >&2 ) || return
         done
     done 3< <( printf '%s\0' "@{!config.setup.zfs.datasets[@]}" | LC_ALL=C sort -z )
+    # zfs list -o name,referenced,encryption,encryptionroot,keylocation,keystatus,mounted,mountpoint
 }
 
 ## Given the name (»datasetPath«) of a ZFS dataset, this deducts crypto-related options from the declared keys (»config.setup.keystore.keys."zfs/..."«).

modules/filesystems/pre-mount-commands.nix.md

@@ -17,6 +17,9 @@ in {
                 This is not implemented for mounts in the initrd (those that are `neededForBoot`) yet.
                 Note that if a symlink exists at a mount point when systemd's fstab-generator runs, it will read/resolve the symlink and use the link's target as the mount point, resulting in mismatching unit names for that mount, effectively disabling its `.preMountCommands`.
                 This does not (apparently and unfortunately) run when mounting via the `mount` command (and probably not with the `mount` system call either).
+            ''; type = lib.types.lines; default = ""; };
+            postUnmountCommands = lib.mkOption { description = ''
+                Like `.preMountCommands`, but runs after unmounting the filesystem.
             ''; type = lib.types.lines; default = ""; };
                 #Also, trying to create the "device" of a "nofail" mount will not work with `mount`, as it will not even attempt to mount anything (and thus not run the `.preMountCommands`) if the "device" is missing.
         }; } ]);
@@ -31,17 +34,19 @@ in {
         }) config.fileSystems;
 
         # The implementation is derived from the "mkfs-${device'}" service in nixpkgs.
-        systemd.services = lib.fun.mapMergeUnique (_: args@{ mountPoint, device, depends, ... }: if (args.preMountCommands != "") then let
+        systemd.services = lib.fun.mapMergeUnique (_: args@{ mountPoint, device, depends, ... }: if (args.preMountCommands != "") || (args.postUnmountCommands != "") then let
             isDevice = lib.fun.startsWith "/dev/" device;
             mountPoint' = utils.escapeSystemdPath mountPoint;
             device' = utils.escapeSystemdPath device;
-        in { "pre-mount-${mountPoint'}" = {
+        in { "pre-mount-${mountPoint'}" = rec {
             description = "Prepare mounting ${device} at ${mountPoint}";
-            wantedBy = [ "${mountPoint'}.mount" ]; before = [ "${mountPoint'}.mount" ];
+            wantedBy = [ "${mountPoint'}.mount" ]; before = wantedBy; partOf = wantedBy;
             requires = lib.optional isDevice "${device'}.device"; after = lib.optional isDevice "${device'}.device";
-            unitConfig.RequiresMountsFor = depends ++ [ (builtins.dirOf device) (builtins.dirOf mountPoint) ];
+            unitConfig.RequiresMountsFor = map utils.escapeSystemdExecArg (depends ++ (lib.optional (lib.hasPrefix "/" device) device) ++ [ (builtins.dirOf mountPoint) ]);
-            unitConfig.DefaultDependencies = false;
+            unitConfig.DefaultDependencies = false; restartIfChanged = false;
-            serviceConfig.Type = "oneshot"; script = args.preMountCommands;
+            serviceConfig.Type = "oneshot"; serviceConfig.RemainAfterExit = true;
+            script = lib.mkIf (args.preMountCommands != "") args.preMountCommands;
+            preStop = lib.mkIf (args.postUnmountCommands != "") args.postUnmountCommands; # ("preStop" still runs post unmount)
         }; } else { }) config.fileSystems;
 
     });