Clean up steam deck config.

nix/steam_deck/configuration/README.org

@@ -0,0 +1,79 @@
+* Initial Setup
+** Mount /home/deck/nix to /nix
+The default /nix is too small and it could be modified by OS releases. We want to use something in our home folder since that will be untouched in upgrades.
+
+# TODO: /home/nix gets owned by root but it should be owned by deck:deck for single-user nix installs
+
+# TODO: nixos-installer adds this to /home/deck/.bash_profile , will this be wiped out in updates?
+# if [ -e /home/deck/.nix-profile/etc/profile.d/nix.sh ]; then . /home/deck/.nix-profile/etc/profile.d/nix.sh; fi # added by Nix installer
+
+Create =/etc/systemd/system/nix-directory.service=
+#+begin_src text
+  [Unit]
+  Description=Create a `/nix` directory to be used for bind mounting
+  #PropagatesStopTo=nix-daemon.service
+  PropagatesStopTo=nix.mount
+  DefaultDependencies=no
+
+  [Service]
+  Type=oneshot
+  ExecStart=steamos-readonly disable
+  ExecStart=mkdir -vp /nix
+  ExecStart=chmod -v 0755 /nix
+  ExecStart=chown -v root /nix
+  ExecStart=chgrp -v root /nix
+  ExecStart=steamos-readonly enable
+  ExecStop=steamos-readonly disable
+  ExecStop=rmdir /nix
+  ExecStop=steamos-readonly enable
+  RemainAfterExit=true
+#+end_src
+
+Create =/etc/systemd/system/nix.mount=
+#+begin_src text
+  [Unit]
+  Description=Mount `/home/nix` on `/nix`
+  #PropagatesStopTo=nix-daemon.service
+  PropagatesStopTo=nix-directory.service
+  After=nix-directory.service
+  Requires=nix-directory.service
+  ConditionPathIsDirectory=/nix
+  DefaultDependencies=no
+  #RequiredBy=nix-daemon.service
+  #RequiredBy=nix-daemon.socket
+
+  [Mount]
+  What=/home/nix
+  Where=/nix
+  Type=none
+  DirectoryMode=0755
+  Options=bind
+#+end_src
+
+Create =/etc/systemd/system/ensure-symlinked-units-resolve.service=
+#+begin_src text
+  [Unit]
+  Description=Ensure Nix related units which are symlinked resolve
+  After=nix.mount
+  Requires=nix-directory.service
+  Requires=nix.mount
+  DefaultDependencies=no
+
+  [Service]
+  Type=oneshot
+  RemainAfterExit=yes
+  ExecStart=/usr/bin/systemctl daemon-reload
+  #ExecStart=/usr/bin/systemctl restart --no-block nix-daemon.socket
+
+  [Install]
+  WantedBy=sysinit.target
+#+end_src
+
+Enable the mount by running
+#+begin_src bash
+  sudo systemctl enable --now ensure-symlinked-units-resolve.service
+#+end_src
+** Install nix
+#+begin_src bash
+  sh <(curl --proto '=https' --tlsv1.2 -L https://nixos.org/nix/install) --no-daemon
+#+end_src