Script to create and restore snapshots of Azure VMs using azure-cli (az)

snapshot.sh

#!/usr/bin/env bash

# Script to create and restore snapshots of the OS disk of Azure VMs

# Copyright 2018 SURFnet B.V.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

function error_exit {
    echo "${1}"
    exit 1
}

# Process options

if [ $# -eq 0 ]; then
    progname=${0##*/}
    echo "Usage: $progname <create | restore> [--group <resource group>] [--name <vm name>] [snapshot name]"
    echo
    echo "This script allows you to:"
    echo "- Create a snapshot of the OS disk of a (running) Azure VM"
    echo "- Restore the OS disk of a Azure VM from a snapshot"
    echo
    echo "THis script requires the 'az' command. This can be installed by running E.g. 'pip install azure-cli'"
    echo "(after install run 'az login')"
    echo
    echo "Options:"
    echo "--group|-g: <resource group> : resource group of the VM"
    echo "--name|-n <vm name> : Virtual machine name"
    echo
    echo "If resource group, vm name or snapshot name are not specified, you will be asked to select them from a list"
    echo
    exit 1
fi

command=$1  # Command to execute
shift
if [[ ! "$command" =~ ^(create|restore)$ ]]; then
    echo "Invalid command '$command'. Allowed commands: 'create' and 'restore'"
    exit 1
fi

group=
vm_name=
snapshot_name=

while [[ $# > 0 ]]
do
option="$1"
shift

case $option in
    -g|--group)
    group="$1"
    if [ -z "$1" ]; then
        error_exit "'$option' option requires an argument"
    fi
    shift
    ;;
    -n|--name)
    vm_name="$1"
    if [ -z "$1" ]; then
        error_exit "'$option' option requires an argument"
    fi
    shift
    ;;
    -*)
    error_exit "Unknown option: '$option'"
    ;;
    *)
    snapshot_name="$option"
    shift
esac
done

AZ=`which az`
if [ "$?" -ne "0" ]; then
   echo "Could not find the 'az' command in the current path. Make sure azure-cli is installed and in the current path."
   echo "Use e.g. 'pip install azure-cli' to install"
   exit 1
fi
echo "Using '$AZ'"


if [ -z "$group" ]; then
    echo "Fetching available resource groups in your subscription"
    az_groups=`$AZ group list --query [].name -o tsv`
    if [ "$?" -ne "0" ]; then
        error_exit "Could not fetch resource groups"
    fi

    echo "Choose resource group:"
    select group in $az_groups; do
        for item in $az_groups; do
            if [ "$item" == "$group"  ]; then
               break 2
            fi
        done
    done
fi

if [ -z "$vm_name" ]; then
    echo "Fetching vm names in resource group '$group'"
    az_names=`$AZ vm list -g "$group" --query [].name -o tsv`
    if [ "$?" -ne "0" ]; then
        error_exit "Could not fetch vm names in resource group '$group'"
    fi

    echo "Choose vm name for which to $command a snapshot:"
    select vm_name in $az_names; do
        for item in $az_names; do
            if [ "$item" == "$vm_name"  ]; then
               break 2
            fi
        done
    done
fi

echo "Selected VM '$vm_name' in resource group '$group'"

echo "Getting VM ID"
vm_id=`$AZ vm show -g $group -n $vm_name --query id -o tsv`
if [ "$?" -ne "0" ]; then
    error_exit "Could not find VM '$vm_name' in resource group '$group'"
fi
echo "VM ID: $vm_id"

out=`$AZ vm show --ids $vm_id --query "[storageProfile.osDisk.managedDisk.id, location] | join(',', @)" -o tsv`
if [ "$?" -ne "0" ]; then
    error_exit "Could get ID of the OS disk"
fi
IFS=',' read current_disk_id vm_location <<< $out

# Handle "create" command
if [ "$command" == "create" ]; then
    while [ -z $snapshot_name ]; do
        echo -n "Enter name for the snapshot to create: "
        read snapshot_name
    done
    echo "About to create snapshot with name '$snapshot_name' of vm '$vm_name' in resource group '$group' in location '$vm_location'."
    read -p "Continue [Y/N]? " -n 1 -r
    echo
    if [[ ! $REPLY =~ ^[Yy]$ ]]; then
        echo "Aborted"
        exit 1
    fi
    echo "Creating a snapshot of disk with ID '$current_disk_id' in location '$vm_location' and resource group '$group'"
    snapshot_id=`$AZ snapshot create -g $group -n $snapshot_name -l $vm_location --source $current_disk_id --query id -o tsv`
    if [ "$?" -ne "0" ]; then
        error_exit "Error creating snapshot"
    fi
    echo 'Created snapshot with ID: snapshot_id'

    echo "Done!"
    echo

    exit 0
# Handle "restore" command
elif [ "$command" == "restore" ]; then
    if [ -z $snapshot_name ]; then
        snapshots=`$AZ snapshot list -g $group --query [].name -o tsv`
        echo "Fetching available snapshots in group $group"
        if [ "$?" -ne "0" ]; then
            error_exit "Could not fetch snapshots in group '$group'"
        fi
        echo "Choose snapshot to restore to vm $vm_name:"
        select snapshot_name in $snapshots; do
            for item in $snapshots; do
                if [ "$item" == "$snapshot_name"  ]; then
                   break 2
                fi
            done
        done
    fi

    echo "About to restore snapshot $snapshot_name to vm '$vm_name' in resource group '$group' in location '$vm_location'"
    echo "The VM will be shutdown and the current OS disk of the VM will be destroyed. The snapshot remains available."
    read -p "Continue [Y/N]? " -n 1 -r
    echo
    if [[ ! $REPLY =~ ^[Yy]$ ]]; then
        echo "Aborted"
        exit 1
    fi

    # Get the ID of the snapshot to restore
    echo "Fetching snapshot ID"
    snapshot_id=`$AZ snapshot show -n $snapshot_name -g $group --query id -o tsv`
    if [ "$?" -ne "0" ]; then
        error_exit "Could not fetch snapshot ID"
    fi
    echo "Snapshot ID: $snapshot_id"

    # Get current OS disk ID from the VM so we can delete it later
    echo "Fetching current OS disk ID"
    current_disk_id=`$AZ vm show --ids $vm_id --query storageProfile.osDisk.managedDisk.id -o tsv`
    if [ "$?" -ne "0" ]; then
        error_exit "Could not fetch current OS disk ID"
    fi
    echo "Current disk ID: $current_disk_id"

    # Create a name for the new disk
    new_disk_name="${vm_name}__${snapshot_name}__`date +%Y-%m-%d_%s`"

    # Create new disk from snapshot
    echo "Creating a new disk with name $new_disk_name from snapshot"
    new_disk_id=`$AZ disk create -n $new_disk_name -g $group --location $vm_location --sku Standard_LRS --source $snapshot_id --query id -o tsv`
    if [ "$?" -ne "0" ]; then
        error_exit "Could not create a new disk from snapshot"
    fi
    echo "Created new disk with ID $new_disk_id"

    # Stop and deallocate the VM
    echo "Stopping the VM"
    $AZ vm stop --ids $vm_id
    if [ "$?" -ne "0" ]; then
        error_exit "Could not stop the VM"
    fi
    echo "VM Stopped"
    echo "Deallocating the VM"
    $AZ vm deallocate --ids $vm_id
    if [ "$?" -ne "0" ]; then
        error_exit "Could deallocate the VM"
    fi
    echo "VM deallocated"

    # Assign new disk to the VM
    echo "Updating the VM to use the new disk"
    upated_vm=`$AZ vm update --ids $vm_id --os-disk $new_disk_id`
    if [ "$?" -ne "0" ]; then
        error_exit "Could not update the VM"
    fi
    echo "VM updated"

    # Start the VM
    echo "Starting the VM"
    $AZ vm start --ids $vm_id
    if [ "$?" -ne "0" ]; then
        echo "Starting the VM failed. You need to manually:"
        echo "- Start the VM: '$AZ vm start --ids $vm_id'"
        echo "- Delete the old disk: '$AZ disk delete --ids $current_disk_id'"
        echo "(Because the VM was deallocated, starting sometimes fails when Azure does not have"
        echo " enough VMs of the required type avaiable)"
        error_exit "Could not start the VM."
    fi
    echo "VM started"

    echo "Deleting the old disk with id $current_disk_id"
    $AZ disk delete --ids $current_disk_id --verbose --yes
    echo "Deleted the old disk"

    echo "Done!"
    echo

    exit 0
else
    error_exit "Don't know how to handle command $command"
fi

@ogenblikje The script gets the location (availability zone) from the current OS disk of the VM and uses that when creating the clone. So the cloned disk and the VM should be in the same location. If you follow the output of the script when cloning and restoring, you should be able to see if/where it goes wrong. The script shows each step it takes in the process.