RootFS Bump for container (for docker 1.12 and above)

# Launch the container from bd_mgmt and invoke the following through a bdconfig command. Two parameters NEW_SIZE and INSTANCE_NAME
# docker run -d --name test bluedata/centos6

INSTANCE_NAME="test"
NEW_SIZE_GB="30"

NEW_SIZE=$(( $NEW_SIZE_GB*1024*1024*1024 ))
CONT_ID=$(docker inspect -f {{.Id}} $INSTANCE_NAME)

DEVMAPPER_POOL=$(docker info | grep pool | awk '{print $3}')

DEV=$(docker inspect -f {{.GraphDriver.Data.DeviceName}} $INSTANCE_NAME)
METADATA_ID=$(echo $DEV  | awk -F "-" '{print $NF}')

# The actual metadata files for this container. We will use this to fetch the current information
# as well as updating after rezize
METADATA_FILE="/var/lib/docker/devicemapper/metadata/$METADATA_ID"
METADATA_INIT_FILE="/var/lib/docker/devicemapper/metadata/$METADATA_ID-init"

# Fetch the current size and the actual device id from the metadata file
OLD_SIZE=$(cat $METADATA_FILE | python -c "import json,sys;obj=json.load(sys.stdin);print obj['size']")
DEVICE_ID=$(cat $METADATA_FILE | python -c "import json,sys;obj=json.load(sys.stdin);print obj['device_id']")

# We got all the information, we can stop the container now. This also deletes the actual
# dm device.
docker stop $INSTANCE_NAME

# Create the same device with the old size
dmsetup create "$DEV" --table "0 $(($OLD_SIZE / 512)) thin /dev/mapper/$DEVMAPPER_POOL $DEVICE_ID"
dmsetup suspend $DEV
# Adjust to new size
dmsetup table $DEV | sed "s/0 [0-9]* thin/0 $(($NEW_SIZE/512)) thin/" | dmsetup load $DEV
# resume. Is this good enough?
dmsetup resume $DEV

# Update metadata
NEW_METADATA_FILE=$(cat $METADATA_FILE | python -c "import json,sys;obj=json.load(sys.stdin);obj['size']=$NEW_SIZE;print json.dumps(obj)")
NEW_METADATA_INIT_FILE=$(cat $METADATA_INIT_FILE | python -c "import json,sys;obj=json.load(sys.stdin);obj['size']=$NEW_SIZE;print json.dumps(obj)")

if [ -n "$NEW_METADATA_FILE" ]
then
    echo -n $NEW_METADATA_FILE > $METADATA_FILE
fi

if [ -n "$NEW_METADATA_INIT_FILE" ]
then
    echo -n $NEW_METADATA_INIT_FILE > $METADATA_INIT_FILE
fi

# Mount the device under some folder and grow the xfs file system
mkdir -p /mnt/test
mount /dev/mapper/$DEV /mnt/test
xfs_growfs /dev/mapper/$DEV
umount /mnt/test

# Start the container 
docker start $INSTANCE_NAME

# To verify after increasing
docker exec -it $INSTANCE_NAME bash -c "df -h /"

# After verifying the new size as 30GB, reboot the box. This is required for future docker start and docker stop of the same 
# container