added functions to create writable partitions from container devices

1 files changed, 59 insertions, 0 deletions

diff --git a/dev_tools/snippets.sh b/dev_tools/snippets.sh
index 02cad0b2..36fc447d 100644
--- a/dev_tools/snippets.sh
+++ b/dev_tools/snippets.sh
@@ -54,3 +54,62 @@ losetup /dev/loop0 persistent_storage.img
 fdisk -lu
 losetup -o $((1050624*512)) /dev/loop0 /dev/nbd0 -v
 mount /dev/loop0 /mnt/
+
+
+
+function create_partition_via_offset() {
+    local device="$1"
+    local nameOrUUID="$2"
+    local loopDevice=$(losetup -f)
+
+    #local sector_size=$(fdisk -l -u $device | grep "Sector size" | cut -d' ' -f4)
+    local sectorSize=$(blockdev --getbsz $device)
+    echo sector size: $sectorSize
+    local partitionInfo=$(partx --raw --noheadings --output START,NAME,UUID /dev/nbd0 2>/dev/null| grep $nameOrUUID)
+    local offsetSectors=$(echo $partitionInfo | cut -d' ' -f1)
+    if [ -z "$offsetSectors" ]; then
+        build_initramfs_log 'error' \
+            "could not find partition with label/uuid '$nameOrUUID' on device $device"
+        return 1
+    fi
+    #echo $(($offsetSectors*512)) # could overflow on 32bit systems
+    offsetBytes=$(echo $| awk -v x=$offsetSectors -v y=$sectorSize '{print x * y}')
+    echo $offsetBytes
+
+    # test if mount works directly (problem with btrfs device id)
+    #mount -v -o loop,offset=$offsetBytes $device $mountPoint
+    losetup -v -o $offsetBytes $loopDevice $device
+    echo $loopDevice
+}
+function make_partition_writable() {
+    local deviceName="$1"
+    local partition="$2"
+    local writable_device="$3"
+
+    local size=$(blockdev --getsz $partition)
+    dmsetup create "$deviceName" --table \
+        "0 $size snapshot $partition $writable_device N 1"
+    mount /dev/mapper/sandbox /mnt
+}
+function make_ram_device() {
+    mknod -m 660 /dev/ram0 b 1 1
+    chown root.disk /dev/ram0
+    echo /dev/ram0
+}
+function make_device_from_file() {
+    local file="$1"
+    local sizeInMegaByte="$2"
+    #modprobe loop
+    local loopDevice=$(losetup -f)
+    dd if=/dev/zero of="$file" bs=1M count=$sizeInMegaByte
+    losetup "$loopDevice" "$file"
+    mkfs.ext4 "$loopDevice"
+    echo $loopDevice
+}
+
+local partition=$(create_partition_via_offset "/dev/nbd0" "system")
+
+local writableDevice=$(make_device_from_file "persistent_storage.img" "50")
+local writableDevice=$(make_ram_device)
+make_partition_writable "sandbox" "$partition" "$writableDevice"
+mount /dev/mapper/sandbox $mountPoint