» QEMU Builder

Type: qemu

The Qemu Packer builder is able to create KVM and Xen virtual machine images.

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.

      "type": "qemu",
      "iso_url": "http://mirror.raystedman.net/centos/6/isos/x86_64/CentOS-6.9-x86_64-minimal.iso",
      "iso_checksum": "af4a1640c0c6f348c6c41f1ea9e192a2",
      "iso_checksum_type": "md5",
      "output_directory": "output_centos_tdhtest",
      "shutdown_command": "echo 'packer' | sudo -S shutdown -P now",
      "disk_size": 5000,
      "format": "qcow2",
      "accelerator": "kvm",
      "http_directory": "path/to/httpdir",
      "ssh_username": "root",
      "ssh_password": "s0m3password",
      "ssh_timeout": "20m",
      "vm_name": "tdhtest",
      "net_device": "virtio-net",
      "disk_interface": "virtio",
      "boot_wait": "10s",
      "boot_command": [
        "<tab> text ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/centos6-ks.cfg<enter><wait>"

This is an example only, and will time out waiting for SSH because we have not provided a kickstart file. You must add a valid kickstart file to the "http_directory" and then provide the file in the "boot_command" in order for this build to run. We recommend you check out the Community Templates for a practical usage example.

» 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.

In addition to the options listed here, a communicator can be configured for this builder.

Note that you will need to set "headless": true if you are running Packer on a Linux server without X11; or if you are connected via ssh to a remote Linux server and have not enabled X11 forwarding (ssh -X).

» 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. At least one of iso_checksum and iso_checksum_url must be defined. This has precedence over iso_checksum_url type.

  • iso_checksum_type (string) - The type of the checksum specified in iso_checksum. Valid values are none, md5, sha1, sha256, or sha512 currently. While none will skip checksumming, this is not recommended since ISO files are generally large and corruption does happen from time to time.

  • iso_checksum_url (string) - A URL to a GNU or BSD style checksum file containing a checksum for the OS ISO file. At least one of iso_checksum and iso_checksum_url must be defined. This will be ignored if iso_checksum is non empty.

  • 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. This can also be a URL to an IMG or QCOW2 file, in which case QEMU will boot directly from it. When passing a path to an IMG or QCOW2 file, you should set disk_image to true.

» Optional:

  • accelerator (string) - The accelerator type to use when running the VM. This may be none, kvm, tcg, hax, hvf, whpx, or xen. The appropriate software must have already been installed on your build machine to use the accelerator you specified. When no accelerator is specified, Packer will try to use kvm if it is available but will default to tcg otherwise.

  • 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 10s or 10 seconds.

  • cpus (number) - The number of cpus to use when building the VM. The default is 1 CPU.

  • disk_additional_size (array of strings) - Additional disks to create. Uses vm_name as the disk name template and appends -# where # is the position in the array. # starts at 1 since 0 is the default disk. Each string represents the disk image size in bytes. Optional suffixes 'k' or 'K' (kilobyte, 1024), 'M' (megabyte, 1024k), 'G' (gigabyte, 1024M), 'T' (terabyte, 1024G), 'P' (petabyte, 1024T) and 'E' (exabyte, 1024P) are supported. 'b' is ignored. Per qemu-img documentation. Each additional disk uses the same disk parameters as the default disk. Unset by default.

  • disk_cache (string) - The cache mode to use for disk. Allowed values include any of writethrough, writeback, none, unsafe or directsync. By default, this is set to writeback.

  • disk_compression (boolean) - Apply compression to the QCOW2 disk file using qemu-img convert. Defaults to false.

  • disk_discard (string) - The discard mode to use for disk. Allowed values include any of unmap or ignore. By default, this is set to ignore.

  • disk_detect_zeroes (string) - The detect-zeroes mode to use for disk. Allowed values include any of unmap, on or off. Defaults to off. When the value is "off" we don't set the flag in the qemu command, so that Packer still works with old versions of QEMU that don't have this option.

  • disk_image (boolean) - Packer defaults to building from an ISO file, this parameter controls whether the ISO URL supplied is actually a bootable QEMU image. When this value is set to true, the machine will either clone the source or use it as a backing file (if use_backing_file is true); then, it will resize the image according to disk_size and boot it.

  • disk_interface (string) - The interface to use for the disk. Allowed values include any of ide, scsi, virtio or virtio-scsi*. 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.

    * Please be aware that use of the scsi disk interface has been disabled by Red Hat due to a bug described here. If you are running Qemu on RHEL or a RHEL variant such as CentOS, you must choose one of the other listed interfaces. Using the scsi interface under these circumstances will cause the build to fail.

  • disk_size (number) - The size, in megabytes, of the hard disk to create for the VM. By default, this is 40960 (40 GB).

  • floppy_dirs (array of strings) - A list of directories to place onto the floppy disk recursively. This is similar to the floppy_files option except that the directory structure is preserved. This is useful for when your floppy disk includes drivers or if you just want to organize it's contents as a hierarchy. Wildcard characters (*, ?, and []) are allowed. The maximum summary size of all files in the listed directories are the same as in floppy_files.

  • floppy_files (array of strings) - A list of files to place onto a floppy disk that is attached when the VM is booted. 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 the floppy is attached as the first floppy device. Currently, no support exists for creating sub-directories on the floppy. Wildcard characters (*, ?, and []) are allowed. Directory names are also allowed, which will add all the files found in the directory to the floppy. The summary size of the listed files must not exceed 1.44 MB. The supported ways to move large files into the OS are using http_directory or the file provisioner.

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

  • headless (boolean) - Packer defaults to building QEMU 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.

    You can still see the console if you make a note of the VNC display number chosen, and then connect using vncviewer -Shared <host>:<display>

  • 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 an empty string, 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 (number) - 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_skip_cache (boolean) - Use iso from provided url. Qemu must support curl block device. This defaults to false.

  • iso_target_extension (string) - The extension of the iso file after download. This defaults to iso.

  • iso_target_path (string) - The path where the iso should be saved after download. By default will go in the packer cache, with a hash of the original filename as its name.

  • 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.

  • machine_type (string) - The type of machine emulation to use. Run your qemu binary with the flags -machine help to list available types for your system. This defaults to pc.

  • memory (number) - The amount of memory to use when building the VM in megabytes. This defaults to 512 megabytes.

  • net_device (string) - The driver to use for the network interface. Allowed values ne2k_pci, i82551, i82557b, i82559er, rtl8139, e1000, pcnet, virtio, virtio-net, virtio-net-pci, usb-net, i82559a, i82559b, i82559c, i82550, i82562, i82557a, i82557c, i82801, vmxnet3, i82558a or i82558b. The Qemu builder uses virtio-net by default.

  • 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.

  • qemu_binary (string) - The name of the Qemu binary to look for. This defaults to qemu-system-x86_64, but may need to be changed for some platforms. For example qemu-kvm, or qemu-system-i386 may be a better choice for some systems.

  • 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 separator.

  • qmp_socket_path (string) - QMP Socket Path when vnc_use_password is true. Defaults to output_directory/vm_name.monitor.

The following shows a sample usage:

  "qemuargs": [
    [ "-m", "1024M" ],
    [ "--no-acpi", "" ],
    [ "-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"

The following shows the environment variable that needs to be set for Windows QEMU support:


You can also use the SSHHostPort template variable to produce a packer template that can be invoked by make in parallel:

  "qemuargs": [
    [ "-netdev", "user,hostfwd=tcp::{{ .SSHHostPort }}-:22,id=forward"],
    [ "-device", "virtio-net,netdev=forward,id=net0"]

make -j 3 my-awesome-packer-templates spawns 3 packer processes, each of which will bind to their own SSH port as determined by each process. This will also work with WinRM, just change the port forward in qemuargs to map to WinRM's default port of 5985 or whatever value you have the service set to listen on.

  • use_backing_file (boolean) - Only applicable when disk_image is true and format is qcow2, set this option to true to create a new QCOW2 file that uses the file located at iso_url as a backing file. The new file will only contain blocks that have changed compared to the backing file, so enabling this option can significantly reduce disk usage.

  • use_default_display (boolean) - If true, do not pass a -display option to qemu, allowing it to choose the default. This may be needed when running under macOS, and getting errors about sdl not being available.

  • 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 unless a shutdown command takes place inside script so this may safely be omitted. It is important to add a shutdown_command. By default Packer halts the virtual machine and the file system may not be sync'd. Thus, changes made in a provisioner might not be saved. If one or more scripts require a reboot it is suggested to leave this blank since reboots may fail and specify the final shutdown command in your last script.

  • 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.

  • skip_compaction (boolean) - Packer compacts the QCOW2 image using qemu-img convert. Set this option to true to disable compacting. Defaults to false.

  • ssh_host_port_min and ssh_host_port_max (number) - 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. By default this is 2222 to 4444.

  • vm_name (string) - This is the name of the image (QCOW2 or IMG) file for the new virtual machine. By default this is packer-BUILDNAME, where "BUILDNAME" is the name of the build. Currently, no file extension will be used unless it is specified in this option.

  • vnc_bind_address (string / IP address) - The IP address that should be binded to for VNC. By default packer will use for this. If you wish to bind to all interfaces use

  • vnc_port_min and vnc_port_max (number) - The minimum and maximum port to use for VNC access to the virtual machine. The builder uses VNC to type the initial boot_command. Because Packer generally runs in parallel, Packer uses a randomly chosen port in this range that appears available. By default this is 5900 to 6000. The minimum and maximum ports are inclusive.

  • vnc_use_password (bool) - Whether or not to set a password on the VNC server. This option automatically enables the QMP socket. See qmp_socket_path. Defaults to false.

» 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.

  "builders": [
      "type": "qemu",
      "boot_key_interval": "10ms"

There are a set of special keys available. If these are in your boot command, they will be replaced by the proper key:

  • <bs> - Backspace

  • <del> - Delete

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

  • <esc> - Simulates pressing the escape key.

  • <tab> - Simulates pressing the tab key.

  • <f1> - <f12> - Simulates pressing a function key.

  • <up> <down> <left> <right> - Simulates pressing an arrow key.

  • <spacebar> - Simulates pressing the spacebar.

  • <insert> - Simulates pressing the insert key.

  • <home> <end> - Simulates pressing the home and end keys.

  • <pageUp> <pageDown> - Simulates pressing the page up and page down keys.

  • <menu> - Simulates pressing the Menu key.

  • <leftAlt> <rightAlt> - Simulates pressing the alt key.

  • <leftCtrl> <rightCtrl> - Simulates pressing the ctrl key.

  • <leftShift> <rightShift> - Simulates pressing the shift key.

  • <leftSuper> <rightSuper> - Simulates pressing the ⌘ or Windows 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.

  • <waitXX> - Add an arbitrary pause before sending any additional keys. The format of XX is a sequence of positive decimal numbers, each with optional fraction and a unit suffix, such as 300ms, 1.5h or 2h45m. Valid time units are ns, us (or µs), ms, s, m, h. For example <wait10m> or <wait1m20s>

» On/Off variants

Any printable keyboard character, and of these "special" expressions, with the exception of the <wait> types, can also be toggled on or off. For example, to simulate ctrl+c, use <leftCtrlOn>c<leftCtrlOff>. Be sure to release them, otherwise they will be held down until the machine reboots.

To hold the c key down, you would use <cOn>. Likewise, <cOff> to release.

» Templates inside boot command

In addition to the special keys, each command to type is treated as a template engine. 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!
  • Name - The name of the VM.

For more examples of various boot commands, see the sample projects from our community templates page.

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

"boot_command": [
    " ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/centos6-ks.cfg<enter>"

For more examples of various boot commands, see the sample projects from our community templates page.

» Troubleshooting

Some users have experienced errors complaining about invalid keymaps. This seems to be related to having a common directory or file in the directory they've run Packer in, like the packer source directory. This appears to be an upstream bug with qemu, and the best solution for now is to remove the file/directory or run in another directory.

Some users have reported issues with incorrect keymaps using qemu version 2.11. This is a bug with qemu, and the solution is to upgrade, or downgrade to 2.10.1 or earlier.