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QEMU Builder

Type: qemu

The Qemu builder is able to create KVM and Xen virtual machine images. Support for Xen is experimanetal at this time.

The builder builds a virtual machine by creating a new virtual machine from scratch, booting it, installing an OS, rebooting the machine with the boot media as the virtual hard drive, provisioning software within the OS, then shutting it down. The result of the Qemu builder is a directory containing the image file necessary to run the virtual machine on KVM or Xen.

Basic Example

Here is a basic example. This example is functional so long as you fixup paths to files, URLS for ISOs and checksums.

{
  "builders":
  [
    {
      "type": "qemu",
      "iso_url": "http://mirror.raystedman.net/centos/6/isos/x86_64/CentOS-6.4-x86_64-minimal.iso",
      "iso_checksum": "4a5fa01c81cc300f4729136e28ebe600",
      "iso_checksum_type": "md5",
      "output_directory": "output_centos_tdhtest",
      "ssh_wait_timeout": "30s",
      "shutdown_command": "shutdown -P now",
      "disk_size": 5000,
      "format": "qcow2",
      "headless": false,
      "accelerator": "kvm",
      "http_directory": "httpdir",
      "http_port_min": 10082,
      "http_port_max": 10089,
      "ssh_host_port_min": 2222,
      "ssh_host_port_max": 2229,
      "ssh_username": "root",
      "ssh_password": "s0m3password",
      "ssh_port": 22,
      "ssh_wait_timeout": "90m",
      "vm_name": "tdhtest",
      "net_device": "virtio-net",
      "disk_interface": "virtio",
      "boot_command":
      [
        "",
        " ks=http://10.0.2.2:{{ .HTTPPort }}/centos6-ks.cfg"
      ]
    }
  ]
}

A working CentOS 6.x kickstart file can be found at this URL, adapted from an unknown source. Place this file in the http directory with the proper name. For the example above, it should go into "httpdir" with a name of "centos6-ks.cfg".

Configuration Reference

There are many configuration options available for the Qemu builder. They are organized below into two categories: required and optional. Within each category, the available options are alphabetized and described.

Required:

  • iso_checksum (string) - The checksum for the OS ISO file. Because ISO files are so large, this is required and Packer will verify it prior to booting a virtual machine with the ISO attached. The type of the checksum is specified with iso_checksum_type, documented below.

  • iso_checksum_type (string) - The type of the checksum specified in iso_checksum. Valid values are "md5", "sha1", "sha256", or "sha512" currently.

  • iso_url (string) - A URL to the ISO containing the installation image. This URL can be either an HTTP URL or a file URL (or path to a file). If this is an HTTP URL, Packer will download it and cache it between runs.

  • ssh_username (string) - The username to use to SSH into the machine once the OS is installed.

Optional:

  • accelerator (string) - The accelerator type to use when running the VM. This may have a value of either "kvm" or "xen" and you must have that support in on the machine on which you run the builder.

  • boot_command (array of strings) - This is an array of commands to type when the virtual machine is first booted. The goal of these commands should be to type just enough to initialize the operating system installer. Special keys can be typed as well, and are covered in the section below on the boot command. If this is not specified, it is assumed the installer will start itself.

  • boot_wait (string) - The time to wait after booting the initial virtual machine before typing the boot_command. The value of this should be a duration. Examples are "5s" and "1m30s" which will cause Packer to wait five seconds and one minute 30 seconds, respectively. If this isn't specified, the default is 10 seconds.

  • disk_size (int) - The size, in megabytes, of the hard disk to create for the VM. By default, this is 40000 (40 GB).

  • disk_interface (string) - The interface to use for the disk. Allowed values include any of "ide," "scsi" or "virtio." Note also that any boot commands or kickstart type scripts must have proper adjustments for resulting device names. The Qemu builder uses "virtio" by default.

  • format (string) - Either "qcow2" or "raw", this specifies the output format of the virtual machine image. This defaults to "qcow2".

  • floppy_files (array of strings) - A list of files to place onto a floppy disk that gets attached when Packer powers up the VM. This is most useful for unattended Windows installs, which look for an Autounattend.xml file on removable media. By default no floppy will be attached. All files listed in this setting get placed into the root directory of the floppy and teh floppy is attached as the first floppy device. Currently, no support exists for sub-directories.

  • headless (bool) - Packer defaults to building virtual machines by launching a GUI that shows the console of the machine being built. When this value is set to true, the machine will start without a console.

  • http_directory (string) - Path to a directory to serve using an HTTP server. The files in this directory will be available over HTTP that will be requestable from the virtual machine. This is useful for hosting kickstart files and so on. By default this is "", which means no HTTP server will be started. The address and port of the HTTP server will be available as variables in boot_command. This is covered in more detail below.

  • http_port_min and http_port_max (int) - These are the minimum and maximum port to use for the HTTP server started to serve the http_directory. Because Packer often runs in parallel, Packer will choose a randomly available port in this range to run the HTTP server. If you want to force the HTTP server to be on one port, make this minimum and maximum port the same. By default the values are 8000 and 9000, respectively.

  • iso_urls (array of strings) - Multiple URLs for the ISO to download. Packer will try these in order. If anything goes wrong attempting to download or while downloading a single URL, it will move on to the next. All URLs must point to the same file (same checksum). By default this is empty and iso_url is used. Only one of iso_url or iso_urls can be specified.

  • net_device (string) - The driver to use for the network interface. Allowed values "ne2k_pci," "i82551," "i82557b," "i82559er," "rtl8139," "e1000," "pcnet" or "virtio." The Qemu builder uses "virtio" by default.

  • qemuargs (array of array of strings) - Allows complete control over the qemu command line (though not, at this time, qemu-img). Each array of strings makes up a command line switch that overrides matching default switch/value pairs. Any value specified as an empty string is ignored. All values after the switch are concatenated with no separater.

    WARNING: The qemu command line allows extreme flexibility, so beware of conflicting arguments causing failures of your run. For instance, using --no-acpi could break the ability to send power signal type commands (e.g., shutdown -P now) to the virtual machine, thus preventing proper shutdown. To see the defaults, look in the packer.log file and search for the qemu-system-x86 command. The arguments are all printed for review.

    The following shows a sample usage:

  . . .
  "qemuargs": [
    [ "-m", "1024m" ],
    [ "--no-acpi", "" ],
    [
       "-netdev",
      "user,id=mynet0,",
      "hostfwd=hostip:hostport-guestip:guestport",
      ""
    ],
    [ "-device", "virtio-net,netdev=mynet0" ]
  ]
  . . .

would produce the following (not including other defaults supplied by the builder and not otherwise conflicting with the qemuargs):

    qemu-system-x86 -m 1024m --no-acpi -netdev user,id=mynet0,hostfwd=hostip:hostport-guestip:guestport -device virtio-net,netdev=mynet0"

  • output_directory (string) - This is the path to the directory where the resulting virtual machine will be created. This may be relative or absolute. If relative, the path is relative to the working directory when packer is executed. This directory must not exist or be empty prior to running the builder. By default this is "output-BUILDNAME" where "BUILDNAME" is the name of the build.

  • run_once (boolean) - When set to true, run_once causes the builder to run Qemu only once, rather than twice. Normally (default false) the builder will run Qemu once for an initial OS install, then switch the CDROM device and boot device for a second run. In that case, Packer does not wait for SSH connections until the second power up of the VM. This approach is often necessary in Linux distribution installs. However, in many Windows unattended installs, the setup handles reboots and dealing with the CDROM as the boot device. With care, a power-down/power-up setting (run_once is set to false) could work if the unattended install is set to restart into audit mode.

  • shutdown_command (string) - The command to use to gracefully shut down the machine once all the provisioning is done. By default this is an empty string, which tells Packer to just forcefully shut down the machine.

  • shutdown_timeout (string) - The amount of time to wait after executing the shutdown_command for the virtual machine to actually shut down. If it doesn't shut down in this time, it is an error. By default, the timeout is "5m", or five minutes.

  • ssh_host_port_min and ssh_host_port_max (uint) - The minimum and maximum port to use for the SSH port on the host machine which is forwarded to the SSH port on the guest machine. Because Packer often runs in parallel, Packer will choose a randomly available port in this range to use as the host port.

  • ssh_key_path (string) - Path to a private key to use for authenticating with SSH. By default this is not set (key-based auth won't be used). The associated public key is expected to already be configured on the VM being prepared by some other process (kickstart, etc.).

  • ssh_password (string) - The password for ssh_username to use to authenticate with SSH. By default this is the empty string.

  • ssh_port (int) - The port that SSH will be listening on in the guest virtual machine. By default this is 22. The Qemu builder will map, via port forward, a port on the host machine to the port listed here so machines outside the installing VM can access the VM.

  • ssh_wait_timeout (string) - The duration to wait for SSH to become available. By default this is "20m", or 20 minutes. Note that this should be quite long since the timer begins as soon as the virtual machine is booted.

  • vm_name (string) - This is the name of the image (QCOW2 or IMG) file for the new virtual machine, without the file extension. By default this is "packer-BUILDNAME", where "BUILDNAME" is the name of the build.

Boot Command

The boot_command configuration is very important: it specifies the keys to type when the virtual machine is first booted in order to start the OS installer. This command is typed after boot_wait, which gives the virtual machine some time to actually load the ISO.

As documented above, the boot_command is an array of strings. The strings are all typed in sequence. It is an array only to improve readability within the template.

The boot command is "typed" character for character over a VNC connection to the machine, simulating a human actually typing the keyboard. There are a set of special keys available. If these are in your boot command, they will be replaced by the proper key:

  • <enter> and <return> - Simulates an actual "enter" or "return" keypress.

  • <esc> - Simulates pressing the escape key.

  • <tab> - Simulates pressing the tab key.

  • <wait> <wait5> <wait10> - Adds a 1, 5 or 10 second pause before sending any additional keys. This is useful if you have to generally wait for the UI to update before typing more.

In addition to the special keys, each command to type is treated as a configuration template. The available variables are:

  • HTTPIP and HTTPPort - The IP and port, respectively of an HTTP server that is started serving the directory specified by the http_directory configuration parameter. If http_directory isn't specified, these will be blank!

Example boot command. This is actually a working boot command used to start an CentOS 6.4 installer:

"boot_command":
[
  "",
  " ks=http://10.0.2.2:{{ .HTTPPort }}/centos6-ks.cfg"
]