Mounting of images without an hierarchical partition structure and a defined / implemented.

If no mount for / (root) at given mount point can be established before mounting a sub partition, a virtual mountpoint
with a small tmpfs (ramdisk) is set up for / (root), so also non hierarchical images without a defined root partition
can be set up. This is usable, if partitions of an image are not mountable at one hierarchical mount tree.
Unmounting the image automatically removes the ram disk.

Signed-off-by: Thomas Mittelstaedt <thomas.mittelstaedt@de.bosch.com>

tools/mountimage

@@ -3,7 +3,7 @@
 #
 # Copyright (c) 2023 Thomas Mittelstaedt <thomas.mittelstaedt@de.bosch.com>
 
-VERSION=2.1.3
+VERSION=2.2.0
 VERSIONDATE=2023
 
 SHORT=hp:m:vr:ulf
@@ -189,11 +189,13 @@ The first valid mount can be setup by an option or be set automatically, if foll
 - GPT partitioning is used
 - One has a partition type "SD_GPT_ROOT*" or "SD_GPT_ESP" (the related UUID) set.
 - A file /etc/fstab exists at this partition
-- If more than one partition have been marked as ROOT partition, the first partition is used
+- If more than one partition has been marked as ROOT partition, the first partition is used
 
 Some information about partition types can be found at:
 https://uapi-group.org/specifications/specs/discoverable_partitions_specification/
 
+If there is still no root partition mountable, a small ramfs file system is created to mount the sub directories
+
 Possible entries for MDESCR:
 
 PARTLABEL=<label>:<mount point>
@@ -316,21 +318,20 @@ local found_valid_root_partition
     root_devices=( $(get_root_partitions ${IMAGE_DEVICE} ${IMAGE_DEVICE_P}) )
     size=${#root_devices[@]}
     if [ "$size" -eq "0" ]; then
-      print_verbose_line "/ is not mounted for $IMAGE_DEVICE, can't handle sub mounts"
-      mdevice=''
-      mbind=''
-    else
-      for id in "${root_devices[@]}"; do
-        mount "$id" "${CMD_MOUNTPOINT}/"
-        check_return_code $? $LINENO
-        if [ -f "${CMD_MOUNTPOINT}/etc/fstab" ]; then
-          break
-        else
-          umount "${CMD_MOUNTPOINT}/"
-          check_return_code $? $LINENO
-        fi
-      done
+      print_verbose_line "/ is not mounted for $IMAGE_DEVICE, creating ramfs as stub"
+      mount -t ramfs -o size=1M ext4 "${CMD_MOUNTPOINT}"
+      check_return_code $? $LINENO
     fi
+    for id in "${root_devices[@]}"; do
+      mount "$id" "${CMD_MOUNTPOINT}/"
+      check_return_code $? $LINENO
+      if [ -f "${CMD_MOUNTPOINT}/etc/fstab" ]; then
+        break
+      else
+        umount "${CMD_MOUNTPOINT}/"
+        check_return_code $? $LINENO
+      fi
+    done
     root_mountpoint=$(findmnt "${CMD_MOUNTPOINT}" -o TARGET  -n)
   fi
   echo "$root_mountpoint"