Revert "MT#62787 Drop /sys/block autodetection code"

This reverts commit 2974f71127.

This breaks our automated VM builds which don't set the target disk.

Change-Id: Iad3c21ae69e983de651fedbc6d50633d2dde0a3b

templates/scripts/includes/deployment.sh

@@ -1794,11 +1794,24 @@ if [[ ${SP_VERSION} =~ ^trunk ]]; then
   TRUNK_VERSION=true
 fi
 
-# iff environment variable TARGET_DISK is set, use it as main disk
-if [ -n "${TARGET_DISK}" ] ; then
+# if TARGET_DISK environment variable is set accept it
+if [ -n "$TARGET_DISK" ] ; then
   export DISK="${TARGET_DISK}"
+else # otherwise try to find sane default
+  if [ -L /sys/block/vda ] ; then
+    export DISK=vda # will be configured as /dev/vda
+  else
+    # in some cases, sda is not the HDD, but the CDROM,
+    # so better walk through all devices.
+    for i in /sys/block/sd*; do
+      if grep -q 0 "${i}/removable"; then
+        DISK=$(basename "$i")
+        export DISK
+        break
+      fi
+    done
+  fi
 fi
-
 if [[ -n "${SWRAID_DISK1}" ]] && [[ -z "${SWRAID_DISK2}" ]] ; then
   die "Error: swraiddisk1 is set, but swraiddisk2 is unset."
 elif [[ -z "${SWRAID_DISK1}" ]] && [[ -n "${SWRAID_DISK2}" ]] ; then