If we could not mount the real root device, or the init program did not exist on it, bail out instead of panicing

In these cases, we will exec /bin/sh, such that manual recovery is still possible as sh has PID 1
An expert might be able to mount and switch_root manually. In any case, this is less scary than a panic and a useless trace.

2 files changed, 21 insertions, 2 deletions

diff --git a/init b/init
index e860047..180ce84 100644
--- a/init
+++ b/init
@@ -180,6 +180,24 @@ else
   nfsmount ${nfs_option:+-o ${nfs_option}} "${nfs_server}:${nfs_path}" /new_root
 fi
 
+[ -z "${init}" ] && init="/sbin/init"
+if [ "$(stat -f -c %i /)" = "$(stat -f -c %i /new_root)" ]; then
+  # Nothing got mounted on /new_root. This is the end, we don't know what to do anymore
+  # We fall back into a shell, but the shell has now PID 1
+  # This way, manual recovery is still possible.
+  err "Failed to mount the real root device."
+  echo "Bailing out, you are on your own. Good luck."
+  echo
+  launch_interactive_shell --exec
+elif [ ! -f "/new_root${init}" ]; then
+  # Successfully mounted /new_root, but ${init} is missing
+  # The same logic as above applies
+  err "Root device mounted successfully, but ${init} does not exist."
+  echo "Bailing out, you are on your own. Good luck."
+  echo
+  launch_interactive_shell --exec
+fi
+
 #Special handling if udev is running
 udevpid=$(/bin/pidof udevd)
 if [ -n "${udevpid}" ]; then
@@ -191,5 +209,4 @@ fi
 
 umount /proc
 umount /sys
-[ -z "${init}" ] && init="/sbin/init"
 exec /sbin/switch_root -c /dev/console /new_root ${init} "$@"
diff --git a/init_functions b/init_functions
index c0f10e9..72bf6ae 100644
--- a/init_functions
+++ b/init_functions
@@ -23,5 +23,7 @@ poll_device() {
 }
 
 launch_interactive_shell() {
-    PS1='[ramfs \W]\$ ' /bin/sh -i
+    PS1='[ramfs \W]\$ '
+    [ "$1" = "--exec" ] && exec /bin/sh -i
+    /bin/sh -i
 }