# libvirt Installation

## Installing from distribution repositories

This is the recommended option to install libvirt. Libvirt is present in the package repositories of all major distributions. Installing a package from the package manager ensures that it's properly compiled, installed, started, and updated during the lifecycle of the distribution.

For users who wish to use the most recent version, certain distributions also allow installing the most recent versions of virtualization packages:

> Fedora

> > Refer to https://fedoraproject.org/wiki/Virtualization_Preview_Repository

> Gentoo

> > The app-emulation/libvirt is regularly updated, but newest versions are usually marked as testing by the ~* keyword.

> openSUSE

> > Refer to https://build.opensuse.org/package/show/Virtualization/libvirt

## Preparing sources

Libvirt can be built both from release tarballs and from a git checkout using the same steps once the source code is prepared. Note that the build system requires that the build directory is separate from the top level source directory.

By default further steps will build libvirt inside a subdirectory of the source tree named build.

Refer to the downloads page for official tarballs and the git repository.

### Unpacking a source tarball

Download a source tarball of the version you want to compile and unpack it using the following commands:

    $ xz -dc libvirt-x.x.x.tar.xz | tar xvf -
    $ cd libvirt-x.x.x

### Git checkout

A git checkout/clone is already in correct state for next steps. Just change your working directory to the checkout.

## Configuring the project

The libvirt build process uses the Meson build system. To configure for a build use the following command. Note that the build argument is the name of the build directory which will be created.

    $ meson setup build [options]

To get the complete list of the options run the following command:

    $ meson configure

Be aware that by default the build is configured with a local prefix path which will not interoperate with OS vendor provided binaries, since the UNIX socket paths will all be different. To produce a build that is compatible with normal OS vendor prefixes, use

    $ meson setup build -Dsystem=true

### Explicitly enabling required functionality

By default each module of functionality of libvirtd is optionally enabled, meaning it will be enabled if the build environment contains the required dependencies.

To ensure that your build contains the required functionality it's recommended to explicitly enable given modules, in which case the configure step will end with an error if dependencies are not present. Example: to build the libvirt project with support for the qemu driver use the following options:

    $ meson setup build -Dsystem=true -Ddriver_qemu=enabled

### Notes:

By default when the meson is run from within a GIT checkout, it will turn on -Werror for builds. This can be disabled with --werror=false, but this is not recommended.

Please ensure that you have the appropriate minimal meson version installed in your build environment. The minimal version for a specific package can be checked in the top level meson.build file in the meson_version field.

DO NOT use the CFLAGS environment variable to set optimizations (e.g. CFLAGS=-O0), but rather use Meson's --optimization=0 option. Certain internal build options are based on the configured optimization value and Meson does not interpret CFLAGS.

## Compiling the sources

Compilation can be carried out by ninja:

    $ ninja -C build

"build" is the path to a directory which must match a path previously given to meson setup.

Binaries and other resulting files can be found within the build directory.

Additionally you can also run the test suite:

    $ ninja -C build test

## Running compiled binaries from build directory

For testing or development purposes it's usually not necessary to install the built binaries into your system. Instead simply run libvirt directly from the source tree. For example to run a privileged libvirtd instance

    $ su -
    # service libvirtd stop  (or systemctl stop libvirtd.service)
    # /home/to/your/checkout/build/src/libvirtd

It is also possible to run virsh directly from the build tree using the ./run script (which sets some environment variables):

    $ pwd
    /home/to/your/checkout/build
    $ ./run ./tools/virsh ....

Note: The libvirt project provides multiple daemons and the above steps may replace only some of them with the custom compiled instances. In most cases this should work but keep that fact in mind.

## Installing compiled binaries

Important: Manual installation of libvirt is generally not recommended and you should prefer installation from your operating system's package repository or from manually built packages which are then installed using the package manager. Overwriting an installation of libvirt from the package manager by a manually compiled installation may not work properly.

Installing the compiled binaries into the appropriate location (based on how the build was configured) is done by the following command:

    $ sudo ninja -C build install

Note the use of sudo with the ninja install command. Using sudo is only required when installing to a location your user does not have write access to. Installing to a system location is a good example of this.

If you are installing to a location that your user does have write access to, then you can instead run the ninja install command without putting sudo before it.

After installation you you may have to run ldconfig or a similar utility to update your list of installed shared libs, or adjust the paths where the system looks for binaries and shared libraries.

The libvirt project provides multiple daemons based on your configuration. You have to ensure that you start the appropriate processes for the freshly installed libvirt to be usable (e.g. even monolithic libvirtd requires in most configurations that virtlogd is started).