Improve the auto disk selection and also apply it for installs as well

as for upgrades.

- For installs, find all and any disks available.
- For upgrades, look for 'a' partitions with the typical root filesystem
  directories in them.

In both cases, if one and only one match is found, it will be selected.

If no disk or multiple disks are found, the installer will require you
to specify a disk, be it by hand or by auto{install,upgrade}.conf.

ok rpe@ krw@ "Innovative." deraadt@

1 files changed, 43 insertions, 15 deletions

diff --git a/distrib/miniroot/install.sub b/distrib/miniroot/install.sub
index be8ee2ad3a6..3d4f97deee3 100644
--- a/distrib/miniroot/install.sub
+++ b/distrib/miniroot/install.sub
@@ -1,5 +1,5 @@
 #!/bin/ksh
-#	$OpenBSD: install.sub,v 1.910 2016/09/04 09:56:46 rpe Exp $
+#	$OpenBSD: install.sub,v 1.911 2016/09/04 10:15:04 halex Exp $
 #
 # Copyright (c) 1997-2015 Todd Miller, Theo de Raadt, Ken Westerback
 # Copyright (c) 2015, Robert Peichaer <rpe@openbsd.org>
@@ -1912,39 +1912,67 @@ set_timezone() {
 	done
 }
 
-# Scan supplied disks and print the first one having a 4.2BSD 'a' partition.
-# If none is found, prints nothing and returns nonzero.
+# Determine if the supplied disk is a potential root disk, by:
+# - Check the disklabel if there is an 'a' partition of type 4.2BSD
+# - Mount the partition (read-only) and look for typical root filesystem layout
+is_rootdisk() {
+	local _d=$1 _rc=1
+
+	(
+		makedev $_d
+		if disklabel $_d | grep -q '^  a: .*4\.2BSD ' &&
+			mount -t ffs -r /dev/${_d}a /mnt; then
+			ls -d /mnt/{bin,dev,etc,home,mnt,root,sbin,tmp,usr,var}
+			_rc=$?
+			umount -f /mnt
+		fi
+		rm -f /dev/{r,}$_d?
+		return $_rc
+	) >/dev/null 2>&1
+}
+
+# From the supplied list of devices, determine a single device suitable
+# for $MODE.
+# On success, prints the device name and returns 0
+# On failure, prints an error message and returns 1
 find_root() {
 	local _d
 
 	for _d; do
-		makedev $_d
-		disklabel "$_d" | grep -q '^  a: .*4\.2BSD ' &&
-			echo $_d && return
-		rm -f /dev/{r,}$_d?
-	done
-	return 1
+		[[ $MODE == upgrade ]] && ! is_rootdisk $_d && continue
+		echo $_d
+	done |
+	(
+		! read first && echo "No root disk found" && exit 1
+
+		! read second && echo $first && exit
+
+		echo "Multiple potential root devices found:" \
+			$(echo $first $second; cat)"."
+		echo "Please specify one."
+		exit 1
+	)
 }
 
 # Get global root information. ie. ROOTDISK, ROOTDEV and SWAPDEV.
 get_rootinfo() {
-	local _auto
-	[[ $MODE == upgrade ]] && _auto=auto
 	while :; do
 		echo "Available disks are: $(get_dkdevs | sed 's/^$/none/')."
 		_ask "Which disk is the root disk? ('?' for details)" \
-			$_auto $(get_dkdevs) || continue
+			auto || continue
 		case $resp in
 		"?")	diskinfo $(get_dkdevs);;
 		'')	;;
-		"$_auto")
-			resp=$(find_root $(get_dkdevs)) && break
-			echo "no disk found"
+		auto)	echo "Scanning disks"
+			resp=$(find_root $(get_dkdevs)) &&
+				echo "Using $resp as root disk" && break
+			echo "$resp"
 			;;
 		*)	isin "$resp" $(get_dkdevs) && break
 			echo "no such disk"
 			;;
 		esac
+		$AUTO && exit 1
 	done
 	makedev $resp || exit