Run a Linux VM on Azure
This article describes a set of proven practices for running a Linux virtual machine (VM) on Azure. It includes recommendations for provisioning the VM along with networking and storage components. Deploy this solution.
Provisioning an Azure VM requires some additional components besides the VM itself, including networking and storage resources.
Resource group. A resource group is a logical container that holds related Azure resources. In general, group resources based on their lifetime and who will manage them.
VM. You can provision a VM from a list of published images, or from a custom managed image or virtual hard disk (VHD) file uploaded to Azure Blob storage. Azure supports running various popular Linux distributions, including CentOS, Debian, Red Hat Enterprise, Ubuntu, and FreeBSD. For more information, see Azure and Linux.
Managed Disks. Azure Managed Disks simplify disk management by handling the storage for you. The OS disk is a VHD stored in Azure Storage, so it persists even when the host machine is down. For Linux VMs, the OS disk is
/dev/sda1. We also recommend creating one or more data disks, which are persistent VHDs used for application data.
Temporary disk. The VM is created with a temporary disk. This disk is stored on a physical drive on the host machine. It is not saved in Azure Storage and may be deleted during reboots and other VM lifecycle events. Use this disk only for temporary data, such as page or swap files. For Linux VMs, the temporary disk is
/dev/sdb1and is mounted at
Virtual network (VNet). Every Azure VM is deployed into a VNet that can be segmented into multiple subnets.
Network interface (NIC). The NIC enables the VM to communicate with the virtual network.
Public IP address. A public IP address is needed to communicate with the VM — for example, via SSH.
Azure DNS. Azure DNS is a hosting service for DNS domains, providing name resolution using Microsoft Azure infrastructure. By hosting your domains in Azure, you can manage your DNS records using the same credentials, APIs, tools, and billing as your other Azure services.
Network security group (NSG). Network security groups are used to allow or deny network traffic to VMs. NSGs can be associated either with subnets or with individual VM instances.
Diagnostics. Diagnostic logging is crucial for managing and troubleshooting the VM.
Azure offers many different virtual machine sizes. For more information, see Sizes for virtual machines in Azure. If you are moving an existing workload to Azure, start with the VM size that's the closest match to your on-premises servers. Then measure the performance of your actual workload with respect to CPU, memory, and disk input/output operations per second (IOPS), and adjust the size as needed. If you require multiple NICs for your VM, be aware that a maximum number of NICs is defined for each VM size.
Generally, choose an Azure region that is closest to your internal users or customers. However, not all VM sizes are available in all regions. For more information, see Services by region. For a list of the VM sizes available in a specific region, run the following command from the Azure command-line interface (CLI):
az vm list-sizes --location <location>
For information about choosing a published VM image, see Find Linux VM images.
Enable monitoring and diagnostics, including basic health metrics, diagnostics infrastructure logs, and boot diagnostics. Boot diagnostics can help you diagnose boot failure if your VM gets into a non-bootable state. For more information, see Enable monitoring and diagnostics.
Disk and storage recommendations
For best disk I/O performance, we recommend Premium Storage, which stores data on solid-state drives (SSDs). Cost is based on the capacity of the provisioned disk. IOPS and throughput (that is, data transfer rate) also depend on disk size, so when you provision a disk, consider all three factors (capacity, IOPS, and throughput).
We also recommend using Managed Disks. Managed disks do not require a storage account. You simply specify the size and type of disk and it is deployed as a highly available resource.
Add one or more data disks. When you create a VHD, it is unformatted. Log into the VM to format the disk. In the Linux shell, data disks are displayed as
/dev/sdd, and so on. You can run
lsblk to list the block devices, including the disks. To use a data disk, create a partition and file system, and mount the disk. For example:
# Create a partition. sudo fdisk /dev/sdc # Enter 'n' to partition, 'w' to write the change. # Create a file system. sudo mkfs -t ext3 /dev/sdc1 # Mount the drive. sudo mkdir /data1 sudo mount /dev/sdc1 /data1
When you add a data disk, a logical unit number (LUN) ID is assigned to the disk. Optionally, you can specify the LUN ID — for example, if you're replacing a disk and want to retain the same LUN ID, or you have an application that looks for a specific LUN ID. However, remember that LUN IDs must be unique for each disk.
You may want to change the I/O scheduler to optimize for performance on SSDs because the disks for VMs with premium storage accounts are SSDs. A common recommendation is to use the NOOP scheduler for SSDs, but you should use a tool such as iostat to monitor disk I/O performance for your workload.
Create a storage account to hold diagnostic logs. A standard locally redundant storage (LRS) account is sufficient for diagnostic logs.
If you aren't using Managed Disks, create separate Azure storage accounts for each VM to hold the virtual hard disks (VHDs), in order to avoid hitting the (IOPS) limits for storage accounts. Be aware of the total I/O limits of the storage account. For more information, see virtual machine disk limits.
The public IP address can be dynamic or static. The default is dynamic.
- Reserve a static IP address if you need a fixed IP address that won't change — for example, if you need to create an A record in DNS, or need the IP address to be added to a safe list.
- You can also create a fully qualified domain name (FQDN) for the IP address. You can then register a CNAME record in DNS that points to the FQDN. For more information, see Create a fully qualified domain name in the Azure portal. You can use Azure DNS or another DNS service.
All NSGs contain a set of default rules, including a rule that blocks all inbound Internet traffic. The default rules cannot be deleted, but other rules can override them. To enable Internet traffic, create rules that allow inbound traffic to specific ports — for example, port 80 for HTTP.
To enable SSH, add an NSG rule that allows inbound traffic to TCP port 22.
For higher availability, deploy multiple VMs in an availability set. This also provides a higher service level agreement (SLA).
To protect against accidental data loss during normal operations (for example, because of user error), you should also implement point-in-time backups, using blob snapshots or another tool.
Resource groups. Put closely associated resources that share the same lifecycle into the same resource group. Resource groups allow you to deploy and monitor resources as a group and track billing costs by resource group. You can also delete resources as a set, which is very useful for test deployments. Assign meaningful resource names to simplify locating a specific resource and understanding its role. For more information, see Recommended naming conventions for Azure resources.
SSH. Before you create a Linux VM, generate a 2048-bit RSA public-private key pair. Use the public key file when you create the VM. For more information, see How to Use SSH with Linux and Mac on Azure.
Stopping a VM. Azure makes a distinction between "stopped" and "deallocated" states. You are charged when the VM status is stopped, but not when the VM is deallocated. In the Azure portal, the Stop button deallocates the VM. If you shut down through the OS while logged in, the VM is stopped but not deallocated, so you will still be charged.
Deleting a VM. If you delete a VM, the VHDs are not deleted. That means you can safely delete the VM without losing data. However, you will still be charged for storage. To delete the VHD, delete the file from Blob storage. To prevent accidental deletion, use a resource lock to lock the entire resource group or lock individual resources, such as a VM.
Use Azure Security Center to get a central view of the security state of your Azure resources. Security Center monitors potential security issues and provides a comprehensive picture of the security health of your deployment. Security Center is configured per Azure subscription. Enable security data collection as described in the Azure Security Center quick start guide. When data collection is enabled, Security Center automatically scans any VMs created under that subscription.
Patch management. If enabled, Security Center checks whether any security and critical updates are missing.
Antimalware. If enabled, Security Center checks whether antimalware software is installed. You can also use Security Center to install antimalware software from inside the Azure portal.
Operations. Use role-based access control (RBAC) to control access to the Azure resources that you deploy. RBAC lets you assign authorization roles to members of your DevOps team. For example, the Reader role can view Azure resources but not create, manage, or delete them. Some roles are specific to particular Azure resource types. For example, the Virtual Machine Contributor role can restart or deallocate a VM, reset the administrator password, create a new VM, and so on. Other built-in RBAC roles that may be useful for this architecture include DevTest Labs User and Network Contributor. A user can be assigned to multiple roles, and you can create custom roles for even more fine-grained permissions.
RBAC does not limit the actions that a user logged into a VM can perform. Those permissions are determined by the account type on the guest OS.
Use audit logs to see provisioning actions and other VM events.
Data encryption. Consider Azure Disk Encryption if you need to encrypt the OS and data disks.
Deploy the solution
A deployment is available on GitHub. It deploys the following:
- A virtual network with a single subnet named web used to host the VM.
- An NSG with two incoming rules to allow SSH and HTTP traffic to the VM.
- A VM running the latest version of Ubuntu 16.04.3 LTS.
- A sample custom script extension that formats the two data disks and deploys Apache HTTP Server to the Ubuntu VM.
Clone, fork, or download the zip file for the reference architectures GitHub repository.
Make sure you have the Azure CLI 2.0 installed on your computer. For CLI installation instructions, see Install Azure CLI 2.0.
Install the Azure building blocks npm package.
From a command prompt, bash prompt, or PowerShell prompt, enter the following command to log into your Azure account.
- Create an SSH key pair. For more information, see How to create and use an SSH public and private key pair for Linux VMs in Azure.
Deploy the solution using azbb
Navigate to the
virtual-machines/single-vm/parameters/linuxfolder for the repository you downloaded in the prerequisites step above.
single-vm-v2.jsonfile and enter a username and your SSH public key between the quotes, then save the file.
"adminUsername": "<your username>", "sshPublicKey": "ssh-rsa AAAAB3NzaC1...",
azbbto deploy the sample VM as shown below.
azbb -s <subscription_id> -g <resource_group_name> -l <location> -p single-vm-v2.json --deploy
To verify the deployment, run the following Azure CLI command to find the public IP address of the VM:
az vm show -n ra-single-linux-vm1 -g <resource-group-name> -d -o table
If you navigate to this address in a web browser, you should see the default Apache2 homepage.