From 927e72eeb82568884eb00896689daedabec6b4f4 Mon Sep 17 00:00:00 2001
From: "Dustin C. Hatch" <dustin@hatch.name>
Date: Sat, 30 Aug 2025 19:29:19 -0500
Subject: [PATCH] Add a root shell on UART console

Until I implement some kind of self-provisioning process for these
machines (supposing I ever do), I need a way to log in and
configure/troubleshoot.  I don't think there's any particular security
concern by having an auto-logged-in root shell on the UART console, as
accessing it needs physical access to the machine.
---
 airplaypi_defconfig.in                        |  1 +
 .../usr/lib/systemd/network/80-wifi.network   |  9 +++++++
 .../systemd/system-preset/50-airplaypi.preset |  1 +
 .../usr/lib/systemd/system/root-shell.service | 24 +++++++++++++++++++
 4 files changed, 35 insertions(+)
 create mode 100644 rootfs-overlay/usr/lib/systemd/network/80-wifi.network
 create mode 100644 rootfs-overlay/usr/lib/systemd/system-preset/50-airplaypi.preset
 create mode 100644 rootfs-overlay/usr/lib/systemd/system/root-shell.service

diff --git a/airplaypi_defconfig.in b/airplaypi_defconfig.in
index 3842af4..8609cdc 100644
--- a/airplaypi_defconfig.in
+++ b/airplaypi_defconfig.in
@@ -6,6 +6,7 @@ BR2_GLOBAL_PATCH_DIR="board/raspberrypi/patches"
 BR2_DOWNLOAD_FORCE_CHECK_HASHES=y
 BR2_TARGET_GENERIC_HOSTNAME="airplaypi"
 BR2_INIT_SYSTEMD=y
+BR2_ROOTFS_OVERLAY="$(WORKSPACE)/rootfs-overlay"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="$(BR2_EXTERNAL_AIMEEOS_PATH)/board/raspberrypi3/post-image.sh"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_TARBALL=y
diff --git a/rootfs-overlay/usr/lib/systemd/network/80-wifi.network b/rootfs-overlay/usr/lib/systemd/network/80-wifi.network
new file mode 100644
index 0000000..587fa07
--- /dev/null
+++ b/rootfs-overlay/usr/lib/systemd/network/80-wifi.network
@@ -0,0 +1,9 @@
+[Match]
+Type=wlan
+
+[Network]
+DHCP=true
+
+[DHCPv4]
+ClientIdentifier=mac
+UseDomain=true
diff --git a/rootfs-overlay/usr/lib/systemd/system-preset/50-airplaypi.preset b/rootfs-overlay/usr/lib/systemd/system-preset/50-airplaypi.preset
new file mode 100644
index 0000000..23eadeb
--- /dev/null
+++ b/rootfs-overlay/usr/lib/systemd/system-preset/50-airplaypi.preset
@@ -0,0 +1 @@
+enable root-shell.service ttyAMA0
diff --git a/rootfs-overlay/usr/lib/systemd/system/root-shell.service b/rootfs-overlay/usr/lib/systemd/system/root-shell.service
new file mode 100644
index 0000000..2cf028a
--- /dev/null
+++ b/rootfs-overlay/usr/lib/systemd/system/root-shell.service
@@ -0,0 +1,24 @@
+[Unit]
+Description=root shell on %I
+Conflicts=getty@%I.service
+Conflicts=serial-getty@%I.service
+
+[Service]
+Environment=TERM=linux
+ExecStart=/bin/sh
+Restart=always
+RestartSec=0
+StandardInput=tty
+TTYPath=/dev/%I
+TTYReset=yes
+TTYVHangup=yes
+KillMode=process
+IgnoreSIGPIPE=no
+KillSignal=SIGHUP
+
+# Unset locale for the console getty since the console has problems
+# displaying some internationalized messages.
+UnsetEnvironment=LANG LANGUAGE LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT LC_IDENTIFICATION
+
+[Install]
+WantedBy=multi-user.target