--- modeline: | vim: set ft=pandoc: description: | The Qemu Packer builder is able to create KVM and Xen virtual machine images. layout: docs page_title: 'QEMU - Builders' sidebar_current: 'docs-builders-qemu' --- # QEMU Builder Type: `qemu` The Qemu Packer builder is able to create [KVM](http://www.linux-kvm.org) and [Xen](http://www.xenproject.org) 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. ``` json { "builders": [ { "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": [ " text ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/centos6-ks.cfg" ] } ] } ``` 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](https://www.packer.io/community-tools.html#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](/docs/templates/communicator.html) 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. -> The `hax` accelerator has issues attaching CDROM ISOs. This is an upstream issue which can be tracked [here](https://github.com/intel/haxm/issues/20). -> The `hvf` and `whpx` accelerator are new and experimental as of [QEMU 2.12.0](https://wiki.qemu.org/ChangeLog/2.12#Host_support). You may encounter issues unrelated to Packer when using these. You may need to add [ "-global", "virtio-pci.disable-modern=on" ] to `qemuargs` depending on the guest operating system. -> For `whpx`, note that [Stefan Weil's QEMU for Windows distribution](https://qemu.weilnetz.de/w64/) does not include WHPX support and users may need to compile or source a build of QEMU for Windows themselves with WHPX support. - `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_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](https://bugzilla.redhat.com/show_bug.cgi?id=1019220). 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](https://www.packer.io/docs/provisioners/file.html). - `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 :` - `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. ~> **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: ``` json { "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): ``` text qemu-system-x86 -m 1024m --no-acpi -netdev user,id=mynet0,hostfwd=hostip:hostport-guestip:guestport -device virtio-net,netdev=mynet0" ``` ~> **Windows Users:** [QEMU for Windows](https://qemu.weilnetz.de/) builds are available though an environmental variable does need to be set for QEMU for Windows to redirect stdout to the console instead of stdout.txt. The following shows the environment variable that needs to be set for Windows QEMU support: ``` text setx SDL_STDIO_REDIRECT=0 ``` You can also use the `SSHHostPort` template variable to produce a packer template that can be invoked by `make` in parallel: ``` json { "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 `127.0.0.1` for this. If you wish to bind to all interfaces use `0.0.0.0`. - `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. ## 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. -> Keystrokes are typed as separate key up/down events over VNC with a default 100ms delay. The delay alleviates issues with latency and CPU contention. You can tune this delay on a per-builder basis by specifying "boot_key_interval" in your Packer template, for example: ``` { "builders": [ { "type": "qemu", "boot_key_interval": "10ms" ... } ] } ``` <%= partial "partials/builders/boot-command" %> Example boot command. This is actually a working boot command used to start an CentOS 6.4 installer: ``` json { "boot_command": [ "", " ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/centos6-ks.cfg" ] } ``` For more examples of various boot commands, see the sample projects from our [community templates page](/community-tools.html#templates). ### 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.