Created new derivation based on this: https://github.com/scawp/Steam-Deck.Mount-External-Drive/

home-manager/hosts/shodan/lillian.nix

@@ -78,14 +78,14 @@
     ungoogled-chromium
   ];
 
-  # Automount services for user
+  # # Automount services for user
-  programs.bashmount.enable = true;
+  # programs.bashmount.enable = true;
-  services.udiskie = {
+  # services.udiskie = {
-    enable = true;
+  #   enable = true;
-    automount = true;
+  #   automount = true;
-    notify = false;
+  #   notify = false;
-    tray = "never";
+  #   tray = "never";
-  };
+  # };
 
   # Enable home-manager and git
   programs.home-manager.enable = true;

nixos/hosts/shodan/auto-mount.nix

@@ -0,0 +1,30 @@
+{
+  inputs,
+  outputs,
+  lib,
+  config,
+  pkgs,
+  ...
+}: {
+  services.udev.extraRules = ''
+    KERNEL=="sd[a-z]|sd[a-z][0-9]", ACTION=="add", RUN+="/bin/systemctl start --no-block external-drive-mount@%k.service"
+    KERNEL=="sd[a-z]|sd[a-z][0-9]", ACTION=="remove", RUN+="/bin/systemctl stop --no-block external-drive-mount@%k.service"
+    KERNEL=="mmcblk0|mmcblk0p[0-9]", ACTION=="add", RUN+="/bin/systemctl start --no-block external-drive-mount@%k.service"
+    KERNEL=="mmcblk0|mmcblk0p[0-9]", ACTION=="remove", RUN+="/bin/systemctl stop --no-block external-drive-mount@%k.service"
+    KERNEL=="nvme0n1p9|nvme0n1p1[0-9]", ACTION=="add", RUN+="/bin/systemctl start --no-block external-drive-mount@%k.service"
+    KERNEL=="nvme0n1p9|nvme0n1p1[0-9]", ACTION=="remove", RUN+="/bin/systemctl stop --no-block external-drive-mount@%k.service"
+  '';
+  systemd.services.auto-mount = {
+    enable = true;
+    description = "Mount External Drive on %i";
+    unitConfig = {
+    };
+    serviceConfig = {
+      Type = "oneshot";
+      ExecStart = "/run/current-system/sw/bin/automount add %i";
+      ExecStop = "/run/current-system/sw/bin/automount remove %i";
+      RemainAfterExit = true;
+    };
+    wantedBy = ["multi-user.target"];
+  };
+}

pkgs/auto-mount/default.nix

@@ -0,0 +1,233 @@
+{
+  lib,
+  stdenv,
+  direnv,
+  writeShellApplication,
+}:
+writeShellApplication
+{
+  name = "auto-mount";
+
+  runtimeInputs = [];
+
+  text = ''
+        #!/bin/bash
+
+    set -euo pipefail
+
+    # Originally from https://serverfault.com/a/767079
+
+    # This script is called from our systemd unit file to mount or unmount
+    # a USB drive.
+
+    usage()
+    {
+        echo "Usage: $0 {add|remove} device_name (e.g. sdb1)"
+        exit 1
+    }
+
+    if [[ $# -ne 2 ]]; then
+        usage
+    fi
+
+    ACTION=$1
+    DEVBASE=$2
+    DEVICE="/dev/''${DEVBASE}"
+
+    # Shared between this and the auto-mount script to ensure we're not double-triggering nor automounting while formatting
+    # or vice-versa.
+    MOUNT_LOCK="/var/run/jupiter-automount-''${DEVBASE//\/_}.lock"
+
+    # Obtain lock
+    exec 9<>"$MOUNT_LOCK"
+    if ! flock -n 9; then
+        echo "$MOUNT_LOCK is active: ignoring action $ACTION"
+        # Do not return a success exit code: it could end up putting the service in 'started' state without doing the mount
+        # work (further start commands will be ignored after that)
+        exit 1
+    fi
+
+    # Wait N seconds for steam
+    wait_steam()
+    {
+        local i=0
+        local wait=$1
+        echo "Waiting up to $wait seconds for steam to load"
+        while ! pgrep -x steamwebhelper &>/dev/null && (( i++ < wait )); do
+            sleep 1
+        done
+    }
+
+    send_steam_url()
+    {
+      local command="$1"
+      local arg="$2"
+      local encoded=$(urlencode "$arg")
+      if pgrep -x "steam" > /dev/null; then
+          # TODO use -ifrunning and check return value - if there was a steam process and it returns -1, the message wasn't sent
+          # need to retry until either steam process is gone or -ifrunning returns 0, or timeout i guess
+          systemd-run -M 1000@ --user --collect --wait sh -c "./.steam/root/ubuntu12_32/steam steam://''${command}/''${encoded@Q}"
+          echo "Sent URL to steam: steam://''${command}/''${arg} (steam://''${command}/''${encoded})"
+      else
+          echo "Could not send steam URL steam://''${command}/''${arg} (steam://''${command}/''${encoded}) -- steam not running"
+      fi
+    }
+
+    # From https://gist.github.com/HazCod/da9ec610c3d50ebff7dd5e7cac76de05
+    urlencode()
+    {
+        [ -z "$1" ] || echo -n "$@" | hexdump -v -e '/1 "%02x"' | sed 's/\(..\)/%\1/g'
+    }
+
+    do_mount()
+    {
+        declare -i ret
+        # NOTE: these values are ABI, since they are sent to the Steam client
+        readonly FSCK_ERROR=1
+        readonly MOUNT_ERROR=2
+
+        # Get info for this drive: $ID_FS_LABEL, and $ID_FS_TYPE
+        dev_json=$(lsblk -o PATH,LABEL,FSTYPE --json -- "$DEVICE" | jq '.blockdevices[0]')
+        ID_FS_LABEL=$(jq -r '.label | select(type == "string")' <<< "$dev_json")
+        ID_FS_TYPE=$(jq -r '.fstype | select(type == "string")' <<< "$dev_json")
+
+        # Global mount options
+        OPTS="rw,noatime"
+
+        # File system type specific mount options
+        #if [[ ''${ID_FS_TYPE} == "vfat" ]]; then
+        #    OPTS+=",users,gid=100,umask=000,shortname=mixed,utf8=1,flush"
+        #fi
+
+            case "''${ID_FS_TYPE}" in
+                    "ntfs")
+              echo "FSType is NTFS"
+              #Extra Opts don't seem necessary anymore? add if required
+              #OPTS+=""
+                        ;;
+                    "exfat")
+              echo "FSType is exFat"
+                        #OPTS+=",users,gid=100,umask=000,shortname=mixed,utf8=1,flush"
+                        ;;
+                    "btrfs")
+              echo "FSType is btrfs"
+                        ;;
+            "ext4")
+                        echo "FSType is ext4"
+              #exit 2
+              ;;
+                    *)
+                        echo "Error mounting ''${DEVICE}: unsupported fstype: ''${ID_FS_TYPE} - ''${dev_json}"
+              rm "''${MOUNT_LOCK}"
+              exit 2
+                        ;;
+            esac
+
+        # Prior to talking to udisks, we need all udev hooks (we were started by one) to finish, so we know it has knowledge
+        # of the drive.  Our own rule starts us as a service with --no-block, so we can wait for rules to settle here
+        # safely.
+        #if ! udevadm settle; then
+        #  echo "Failed to wait for \`udevadm settle\`"
+        #  exit 1
+        #fi
+
+        # Ask udisks to auto-mount. This needs a version of udisks that supports the 'as-user' option.
+        ret=0
+        reply=$(busctl call --allow-interactive-authorization=false --expect-reply=true --json=short   \
+                    org.freedesktop.UDisks2                                                            \
+                    /org/freedesktop/UDisks2/block_devices/"''${DEVBASE}"                                \
+                    org.freedesktop.UDisks2.Filesystem                                                 \
+                    Mount 'a{sv}' 3                                                                    \
+                      as-user s lillian                                                                   \
+                      auth.no_user_interaction b true                                                  \
+                      options                  s "$OPTS") || ret=$?
+
+        if (( ret != 0 )); then
+            send_steam_url "system/devicemountresult" "''${DEVBASE}/''${MOUNT_ERROR}"
+            echo "Error mounting ''${DEVICE} (status = $ret)"
+            exit 1
+        fi
+
+        # Expected reply is of the format
+        #  {"type":"s","data":["/run/media/lillian/home"]}
+        mount_point=$(jq -r '.data[0] | select(type == "string")' <<< "$reply" || true)
+        if [[ -z $mount_point ]]; then
+            echo "Error when mounting ''${DEVICE}: udisks returned success but could not parse reply:"
+            echo "---"$'\n'"$reply"$'\n'"---"
+            exit 1
+        fi
+
+        if [[ ''${ID_FS_TYPE} == "exfat" ]]; then
+            echo "exFat does not support symlinks, do not add library to Steam"
+            exit 0
+        fi
+
+        # Create a symlink from /run/media to keep compatibility with apps
+        # that use the older mount point (for SD cards only).
+        case "''${DEVBASE}" in
+            mmcblk0p*)
+                if [[ -z "''${ID_FS_LABEL}" ]]; then
+                    old_mount_point="/run/media/''${DEVBASE}"
+                else
+                    old_mount_point="/run/media/''${mount_point##*/}"
+                fi
+                if [[ ! -d "''${old_mount_point}" ]]; then
+                    rm -f -- "''${old_mount_point}"
+                    ln -s -- "''${mount_point}" "''${old_mount_point}"
+                fi
+                ;;
+        esac
+
+        echo "**** Mounted ''${DEVICE} at ''${mount_point} ****"
+
+        if [ -f "''${mount_point}/libraryfolder.vdf" ]; then
+            send_steam_url "addlibraryfolder" "''${mount_point}"
+        else
+            #TODO check permissions are 1000  when creating new SteamLibrary
+            mkdir -p "''${mount_point}/SteamLibrary"
+            chown lillian:lillian "''${mount_point}/SteamLibrary"
+            send_steam_url "addlibraryfolder" "''${mount_point}/SteamLibrary"
+        fi
+    }
+
+    do_unmount()
+    {
+        local mount_point=$(findmnt -fno TARGET "''${DEVICE}" || true)
+        if [[ -n $mount_point ]]; then
+            # Remove symlink to the mount point that we're unmounting
+            find /run/media -maxdepth 1 -xdev -type l -lname "''${mount_point}" -exec rm -- {} \;
+        else
+            # If we don't know the mount point then remove all broken symlinks
+            find /run/media -maxdepth 1 -xdev -xtype l -exec rm -- {} \;
+        fi
+    }
+
+    do_retrigger()
+    {
+        local mount_point=$(findmnt -fno TARGET "''${DEVICE}" || true)
+        [[ -n $mount_point ]] || return 0
+
+        # In retrigger mode, we want to wait a bit for steam as the common pattern is starting in parallel with a retrigger
+        wait_steam 10
+        # This is a truly gnarly way to ensure steam is ready for commands.
+        # TODO literally anything else
+        sleep 6
+        send_steam_url "addlibraryfolder" "''${mount_point}"
+    }
+
+    case "''${ACTION}" in
+        add)
+            do_mount
+            ;;
+        remove)
+            do_unmount
+            ;;
+        retrigger)
+            do_retrigger
+            ;;
+        *)
+            usage
+            ;;
+    esac
+  '';
+}

pkgs/default.nix

@@ -11,4 +11,5 @@ pkgs: {
   update = pkgs.callPackage ./update {};
   upgrade = pkgs.callPackage ./upgrade {};
   restart = pkgs.callPackage ./restart {};
+  auto-mount = pkgs.callPackage ./auto-mount {};
 }