Microsoft Azure Linux Agent

Linux distributions support

Our daily automation tests most of the Linux distributions supported by Azure; the Agent can be used on other distributions as well, but development, testing and support for those are done by the open source community.

Testing is done using the develop branch, which can be unstable. For a stable build please use the master branch instead.

Introduction

The Microsoft Azure Linux Agent (waagent) manages Linux provisioning and VM interaction with the Azure Fabric Controller. It provides the following functionality for Linux IaaS deployments:

• Image Provisioning

  • Creation of a user account
  • Configuring SSH authentication types
  • Deployment of SSH public keys and key pairs
  • Setting the host name
  • Publishing the host name to the platform DNS
  • Reporting SSH host key fingerprint to the platform
  • Resource Disk Management
  • Formatting and mounting the resource disk
  • Configuring swap space

• Networking

  • Manages routes to improve compatibility with platform DHCP servers
  • Ensures the stability of the network interface name

• Kernel

  • Configure virtual NUMA (disable for kernel <2.6.37)
  • Configure SCSI timeouts for the root device (which could be remote)

• Diagnostics

  • Console redirection to the serial port

• SCVMM Deployments

  • Detect and bootstrap the VMM agent for Linux when running in a System Center Virtual Machine Manager 2012R2 environment

• VM Extension

  • Inject component authored by Microsoft and Partners into Linux VM (IaaS) to enable software and configuration automation
  • VM Extension reference implementation on GitHub

Communication

The information flow from the platform to the agent occurs via two channels:

• A boot-time attached DVD for IaaS deployments. This DVD includes an OVF-compliant configuration file that includes all provisioning information other than the actual SSH keypairs.

• A TCP endpoint exposing a REST API used to obtain deployment and topology configuration.

The agent will use an HTTP proxy if provided via the http_proxy (for http requests) or https_proxy (for https requests) environment variables. The HttpProxy.Host and HttpProxy.Port configuration variables (see below), if used, will override the environment settings. Due to limitations of Python, the agent does not support HTTP proxies requiring authentication. Note that when the agent service is managed by systemd, environment variables such as http_proxy and https_proxy should be defined using one the mechanisms provided by systemd (e.g. by using Environment or EnvironmentFile in the service file).

Requirements

The following systems have been tested and are known to work with the Azure Linux Agent. Please note that this list may differ from the official list of supported systems on the Microsoft Azure Platform as described here.

Waagent depends on some system packages in order to function properly:

• Python 2.6+
• OpenSSL 1.0+
• OpenSSH 5.3+
• Filesystem utilities: sfdisk, fdisk, mkfs, parted
• Password tools: chpasswd, sudo
• Text processing tools: sed, grep
• Network tools: ip-route

Installation

Installation via your distribution's package repository is preferred. You can also customize your own RPM or DEB packages using the configuration samples provided (see deb and rpm sections below).

For more advanced installation options, such as installing to custom locations or prefixes, you can use setuptools to install from source by running:

    sudo python setup.py install --register-service

For Python 3, use:

    sudo python3 setup.py install --register-service

You can view more installation options by running:

    sudo python setup.py install --help

The agent's log file is kept at /var/log/waagent.log.

Upgrade

Upgrading via your distribution's package repository is strongly preferred.

If upgrading manually, same with installation above by running:

    sudo python setup.py install --force

Restart waagent service,for most of linux distributions:

    sudo service waagent restart

For Ubuntu, use:

    sudo service walinuxagent restart

For CoreOS, use:

    sudo systemctl restart waagent

Command line options

Flags

-verbose: Increase verbosity of specified command

-force: Skip interactive confirmation for some commands

Commands

-help: Lists the supported commands and flags.

-deprovision: Attempt to clean the system and make it suitable for re-provisioning, by deleting the following:

• All SSH host keys (if Provisioning.RegenerateSshHostKeyPair is 'y' in the configuration file)

• Nameserver configuration in /etc/resolv.conf

• Root password from /etc/shadow (if Provisioning.DeleteRootPassword is 'y' in the configuration file)

• Cached DHCP client leases

• Resets host name to localhost.localdomain

  WARNING! Deprovision does not guarantee that the image is cleared of all sensitive information and suitable for redistribution.

-deprovision+user: Performs everything under deprovision (above) and also deletes the last provisioned user account and associated data.

-version: Displays the version of waagent

-serialconsole: Configures GRUB to mark ttyS0 (the first serial port) as the boot console. This ensures that kernel bootup logs are sent to the serial port and made available for debugging.

-daemon: Run waagent as a daemon to manage interaction with the platform. This argument is specified to waagent in the waagent init script.

-start: Run waagent as a background process

-collect-logs [-full]: Runs the log collector utility that collects relevant agent logs for debugging and stores them in the agent folder on disk. Exact location will be shown when run. Use flag -full for more exhaustive log collection.

Configuration

A configuration file (/etc/waagent.conf) controls the actions of waagent. Blank lines and lines whose first character is a # are ignored (end-of-line comments are not supported).

A sample configuration file is shown below:

Extensions.Enabled=y
Extensions.GoalStatePeriod=6
Provisioning.Agent=auto
Provisioning.DeleteRootPassword=n
Provisioning.RegenerateSshHostKeyPair=y
Provisioning.SshHostKeyPairType=rsa
Provisioning.MonitorHostName=y
Provisioning.DecodeCustomData=n
Provisioning.ExecuteCustomData=n
Provisioning.PasswordCryptId=6
Provisioning.PasswordCryptSaltLength=10
ResourceDisk.Format=y
ResourceDisk.Filesystem=ext4
ResourceDisk.MountPoint=/mnt/resource
ResourceDisk.MountOptions=None
ResourceDisk.EnableSwap=n
ResourceDisk.EnableSwapEncryption=n
ResourceDisk.SwapSizeMB=0
Logs.Verbose=n
Logs.Collect=y
Logs.CollectPeriod=3600
OS.AllowHTTP=n
OS.RootDeviceScsiTimeout=300
OS.EnableFIPS=n
OS.OpensslPath=None
OS.SshClientAliveInterval=180
OS.SshDir=/etc/ssh
HttpProxy.Host=None
HttpProxy.Port=None

The various configuration options are described in detail below. Configuration options are of three types : Boolean, String or Integer. The Boolean configuration options can be specified as "y" or "n". The special keyword "None" may be used for some string type configuration entries as detailed below.

Configuration File Options

Extensions.Enabled

Type: Boolean
Default: y

This allows the user to enable or disable the extension handling functionality in the agent. Valid values are "y" or "n". If extension handling is disabled, the goal state will still be processed and VM status is still reported, but only every 5 minutes. Extension config within the goal state will be ignored. Note that functionality such as password reset, ssh key updates and backups depend on extensions. Only disable this if you do not need extensions at all.

Note: disabling extensions in this manner is not the same as running completely without the agent. In order to do that, the provisionVMAgent flag must be set at provisioning time, via whichever API is being used. We will provide more details on this on our wiki when it is generally available.

Extensions.GoalStatePeriod

Type: Integer
Default: 6

How often to poll for new goal states (in seconds) and report the status of the VM and extensions. Goal states describe the desired state of the extensions on the VM.

Note: setting up this parameter to more than a few minutes can make the state of the VM be reported as unresponsive/unavailable on the Azure portal. Also, this setting affects how fast the agent starts executing extensions.

AutoUpdate.Enabled

Type: Boolean
Default: y

Enables auto-update of the Extension Handler. The Extension Handler is responsible for managing extensions and reporting VM status. The core functionality of the agent is contained in the Extension Handler, and we encourage users to enable this option in order to maintain an up to date version.

On most distros the default value is 'y'.

For more information on the agent version, see our FAQ.

Provisioning.Agent

Type: String Default: auto

Choose which provisioning agent to use (or allow waagent to figure it out by specifying "auto"). Possible options are "auto" (default), "waagent", "cloud-init", or "disabled".

Provisioning.Enabled (removed in 2.2.45)

Type: Boolean Default: y

This allows the user to enable or disable the provisioning functionality in the agent. Valid values are "y" or "n". If provisioning is disabled, SSH host and user keys in the image are preserved and any configuration specified in the Azure provisioning API is ignored.

Note: This configuration option has been removed and has no effect. waagent now auto-detects cloud-init as a provisioning agent (with an option to override with Provisioning.Agent).

Provisioning.MonitorHostName

Type: Boolean Default: n

Monitor host name changes and publish changes via DHCP requests.

Provisioning.MonitorHostNamePeriod

Type: Integer Default: 30

How often to monitor host name changes (in seconds). This setting is ignored if MonitorHostName is not set.

Provisioning.UseCloudInit

Type: Boolean Default: n

This options enables / disables support for provisioning by means of cloud-init. When true ("y"), the agent will wait for cloud-init to complete before installing extensions and processing the latest goal state. Provisioning.Enabled must be disabled ("n") for this option to have an effect. Setting Provisioning.Enabled to true ("y") overrides this option and runs the built-in agent provisioning code.

Note: This configuration option has been removed and has no effect. waagent now auto-detects cloud-init as a provisioning agent (with an option to override with Provisioning.Agent).

Provisioning.DeleteRootPassword

Type: Boolean
Default: n

If set, the root password in the /etc/shadow file is erased during the provisioning process.

Provisioning.RegenerateSshHostKeyPair

Type: Boolean
Default: y

If set, all SSH host key pairs (ecdsa, dsa and rsa) are deleted during the provisioning process from /etc/ssh/. And a single fresh key pair is generated. The encryption type for the fresh key pair is configurable by the Provisioning.SshHostKeyPairType entry. Please note that some distributions will re-create SSH key pairs for any missing encryption types when the SSH daemon is restarted (for example, upon a reboot).

Provisioning.SshHostKeyPairType

Type: String
Default: rsa

This can be set to an encryption algorithm type that is supported by the SSH daemon on the VM. The typically supported values are "rsa", "dsa" and "ecdsa". Note that "putty.exe" on Windows does not support "ecdsa". So, if you intend to use putty.exe on Windows to connect to a Linux deployment, please use "rsa" or "dsa".

Provisioning.MonitorHostName

Type: Boolean
Default: y

If set, waagent will monitor the Linux VM for hostname changes (as returned by the "hostname" command) and automatically update the networking configuration in the image to reflect the change. In order to push the name change to the DNS servers, networking will be restarted in the VM. This will result in brief loss of Internet connectivity.

Provisioning.DecodeCustomData

Type: Boolean
Default: n

If set, waagent will decode CustomData from Base64.

Provisioning.ExecuteCustomData

Type: Boolean
Default: n

If set, waagent will execute CustomData after provisioning.

Provisioning.PasswordCryptId

Type: String
Default: 6

Algorithm used by crypt when generating password hash.

• 1 - MD5
• 2a - Blowfish
• 5 - SHA-256
• 6 - SHA-512

Provisioning.PasswordCryptSaltLength

Type: String
Default: 10

Length of random salt used when generating password hash.

ResourceDisk.Format

Type: Boolean
Default: y

If set, the resource disk provided by the platform will be formatted and mounted by waagent if the filesystem type requested by the user in "ResourceDisk.Filesystem" is anything other than "ntfs". A single partition of type Linux (83) will be made available on the disk. Note that this partition will not be formatted if it can be successfully mounted.

ResourceDisk.Filesystem

Type: String
Default: ext4

This specifies the filesystem type for the resource disk. Supported values vary by Linux distribution. If the string is X, then mkfs.X should be present on the Linux image. SLES 11 images should typically use 'ext3'. BSD images should use 'ufs2' here.

ResourceDisk.MountPoint

Type: String
Default: /mnt/resource

This specifies the path at which the resource disk is mounted.

ResourceDisk.MountOptions

Type: String
Default: None

Specifies disk mount options to be passed to the mount -o command. This is a comma separated list of values, ex. 'nodev,nosuid'. See mount(8) for details.

ResourceDisk.EnableSwap

Type: Boolean
Default: n

If set, a swap file (/swapfile) is created on the resource disk and added to the system swap space.

ResourceDisk.EnableSwapEncryption

Type: Boolean
Default: n

If set, the swap file (/swapfile) is mounted as an encrypted filesystem (flag supported only on FreeBSD.)

ResourceDisk.SwapSizeMB

Type: Integer
Default: 0

The size of the swap file in megabytes.

Logs.Verbose

Type: Boolean
Default: n

If set, log verbosity is boosted. Waagent logs to /var/log/waagent.log and leverages the system logrotate functionality to rotate logs.

Logs.Collect

Type: Boolean
Default: y

If set, agent logs will be periodically collected and uploaded to a secure location for improved supportability.

NOTE: This feature relies on the agent's resource usage features (cgroups); this flag will not take effect on any distro not supported.

Logs.CollectPeriod

Type: Integer
Default: 3600

This configures how frequently to collect and upload logs. Default is each hour.

NOTE: This only takes effect if the Logs.Collect option is enabled.

OS.AllowHTTP

Type: Boolean
Default: n

If SSL support is not compiled into Python, the agent will fail all HTTPS requests. You can set this option to 'y' to make the agent fall-back to HTTP, instead of failing the requests.

NOTE: Allowing HTTP may unintentionally expose secure data.

OS.EnableRDMA

Type: Boolean
Default: n

If set, the agent will attempt to install and then load an RDMA kernel driver that matches the version of the firmware on the underlying hardware.

OS.EnableFIPS

Type: Boolean
Default: n

If set, the agent will emit into the environment "OPENSSL_FIPS=1" when executing OpenSSL commands. This signals OpenSSL to use any installed FIPS-compliant libraries. Note that the agent itself has no FIPS-specific code. If no FIPS-compliant certificates are installed, then enabling this option will cause all OpenSSL commands to fail.

OS.MonitorDhcpClientRestartPeriod

Type: Integer Default: 30

The agent monitor restarts of the DHCP client and restores network rules when it happens. This setting determines how often (in seconds) to monitor for restarts.

OS.RootDeviceScsiTimeout

Type: Integer
Default: 300

This configures the SCSI timeout in seconds on the root device. If not set, the system defaults are used.

OS.RootDeviceScsiTimeoutPeriod

Type: Integer
Default: 30

How often to set the SCSI timeout on the root device (in seconds). This setting is ignored if RootDeviceScsiTimeout is not set.

OS.OpensslPath

Type: String
Default: None

This can be used to specify an alternate path for the openssl binary to use for cryptographic operations.

OS.RemovePersistentNetRulesPeriod

Type: Integer
Default: 30

How often to remove the udev rules for persistent network interface names (75-persistent-net-generator.rules and /etc/udev/rules.d/70-persistent-net.rules) (in seconds)

OS.SshClientAliveInterval

Type: Integer
Default: 180

This values sets the number of seconds the agent uses for the SSH ClientAliveInterval configuration option.

OS.SshDir

Type: String
Default: /etc/ssh

This option can be used to override the normal location of the SSH configuration directory.

HttpProxy.Host, HttpProxy.Port

Type: String
Default: None

If set, the agent will use this proxy server to access the internet. These values will override the http_proxy or https_proxy environment variables. Lastly, HttpProxy.Host is required (if to be used) and HttpProxy.Port is optional.

CGroups.EnforceLimits

Type: Boolean
Default: y

If set, the agent will attempt to set cgroups limits for cpu and memory for the agent process itself as well as extension processes. See the wiki for further details on this.

CGroups.Excluded

Type: String
Default: customscript,runcommand

The list of extensions which will be excluded from cgroups limits. This should be comma separated.

Telemetry

WALinuxAgent collects usage data and sends it to Microsoft to help improve our products and services. The data collected is used to track service health and assist with Azure support requests. Data collected does not include any personally identifiable information. Read our privacy statement to learn more.

WALinuxAgent does not support disabling telemetry at this time. WALinuxAgent must be removed to disable telemetry collection. If you need this feature, please open an issue in GitHub and explain your requirement.

Appendix

We do not maintain packaging information in this repo but some samples are shown below as a reference. See the downstream distribution repositories for officially maintained packaging.

deb packages

The official Ubuntu WALinuxAgent package can be found here.

Run once:

1. Install required packages

   sudo apt-get -y install ubuntu-dev-tools pbuilder python-all debhelper

2. Create the pbuilder environment

   sudo pbuilder create --debootstrapopts --variant=buildd

3. Obtain waagent.dsc from a downstream package repo

To compile the package, from the top-most directory:

1. Build the source package

   dpkg-buildpackage -S

2. Build the package

   sudo pbuilder build waagent.dsc

3. Fetch the built package, usually from /var/cache/pbuilder/result

rpm packages

The instructions below describe how to build an rpm package.

1. Install setuptools

   curl https://bootstrap.pypa.io/ez_setup.py -o - | python

2. The following command will build the binary and source RPMs:

   python setup.py bdist_rpm

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.