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---
description: |
The Qemu Packer builder is able to create KVM and Xen virtual machine images.
Support for Xen is experimental at this time.
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. Support for Xen is
experimental 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.
``` json
{
"builders":
[
{
"type": "qemu",
"iso_url": "http://mirror.raystedman.net/centos/6/isos/x86_64/CentOS-6.8-x86_64-minimal.iso",
"iso_checksum": "0ca12fe5f28c2ceed4f4084b41ff8a0b",
"iso_checksum_type": "md5",
"output_directory": "output_centos_tdhtest",
"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": "30s",
"vm_name": "tdhtest",
"net_device": "virtio-net",
"disk_interface": "virtio",
"boot_wait": "5s",
"boot_command": [
"<tab> text ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/centos6-ks.cfg<enter><wait>"
]
}
]
}
```
A working CentOS 6.x kickstart file can be found [at this
URL](https://gist.github.com/mitchellh/7328271/#file-centos6-ks-cfg), 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.
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".
- `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 be `none`, `kvm`, `tcg`, or `xen`. The appropriate software must
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 10 seconds.
- `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_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 clone the
source, resize it according to `disk_size` and boot the image.
- `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` (integer) - The size, in megabytes, of the hard disk to create
for the VM. By default, this is 40000 (about 40 GB).
- `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).
- `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`.
- `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 "", 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` (integer) - 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".
- `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.
~&gt; **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"
```
~&gt; **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_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 OS X.
- `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. 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` (integer) - 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` (integer) - 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.
-&gt; 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. For local builds you can tune this delay by specifying
e.g. `PACKER_KEY_INTERVAL=10ms` to speed through the boot command.
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>` and `<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.
- `<leftAlt>` `<rightAlt>` - Simulates pressing the alt key.
- `<leftCtrl>` `<rightCtrl>` - Simulates pressing the ctrl key.
- `<leftShift>` `<rightShift>` - Simulates pressing the shift key.
- `<leftAltOn>` `<rightAltOn>` - Simulates pressing and holding the alt key.
- `<leftCtrlOn>` `<rightCtrlOn>` - Simulates pressing and holding the ctrl key.
- `<leftShiftOn>` `<rightShiftOn>` - Simulates pressing and holding the shift key.
- `<leftAltOff>` `<rightAltOff>` - Simulates releasing a held alt key.
- `<leftCtrlOff>` `<rightCtrlOff>` - Simulates releasing a held ctrl key.
- `<leftShiftOff>` `<rightShiftOff>` - Simulates releasing a held shift 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 user defined time.Duration pause before sending any
additional keys. For example `<wait10m>` or `<wait1m20s>`
When using modifier keys `ctrl`, `alt`, `shift` ensure that you release them,
otherwise they will be held down until the machine reboots. Use lowercase
characters as well inside modifiers. For example: to simulate ctrl+c use
`<leftCtrlOn>c<leftCtrlOff>`.
In addition to the special keys, each command to type is treated as a
[template engine](/docs/templates/engine.html). 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:
``` json
{
"boot_command": [
"<tab><wait>",
" ks=http://{{ .HTTPIP }}:{{ .HTTPPort }}/centos6-ks.cfg<enter>"
]
}
```
### 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.
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