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Currently, nbdkit support will automatically be enabled as long as the pidfd_open(2) syscall is available. Optionally, libnbd is used to generate more user-friendly error messages. In theory this is all good, since use of nbdkit is supposed to be transparent to the user. In practice, however, there is a problem: if support for it is enabled at build time and the necessary runtime components are installed, nbdkit will always be preferred, with no way for the user to opt out. This will arguably be fine in the long run, but right now none of the platforms that we target ships with a SELinux policy that allows libvirt to launch nbdkit, and the AppArmor policy that we maintain ourselves hasn't been updated either. So, in practice, as of today having nbdkit installed on the host makes network disks completely unusable unless you're willing to compromise the overall security of the system by disabling SELinux/AppArmor. In order to make the transition smoother, provide a convenient way for users and distro packagers to disable nbdkit support at compile time until SELinux and AppArmor are ready. In the process, detection is completely overhauled. libnbd is made mandatory when nbdkit support is enabled, since availability across operating systems is comparable and offering users the option to make error messages worse doesn't make a lot of sense; we also make sure that an explicit request from the user to enable/disable nbdkit support is either complied with, or results in a build failure when that's not possible. Last but not least, we avoid linking against libnbd when nbdkit support is disabled. At the RPM level, we disable the feature when building against anything older than Fedora 40, which still doesn't have the necessary SELinux bits but will hopefully gain them by the time it's released. We also allow nbdkit support to be disabled at build time the same way as other optional features, that is, by passing "--define '_without_nbdkit 1'" to rpmbuild. Finally, if nbdkit support has been disabled, installing libvirt will no longer drag it in as a (weak) dependency. Signed-off-by: Andrea Bolognani <abologna@redhat.com> Reviewed-by: Jonathon Jongsma <jjongsma@redhat.com>
Libvirt API for virtualization
Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
For some of these hypervisors, it provides a stateful management daemon which runs on the virtualization host allowing access to the API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other languages including Python, Perl, PHP, Go, Java, OCaml, as well as mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the website:
License
The libvirt C API is distributed under the terms of GNU Lesser General Public License, version 2.1 (or later). Some parts of the code that are not part of the C library may have the more restrictive GNU General Public License, version 2.0 (or later). See the files COPYING.LESSER and COPYING for full license terms & conditions.
Installation
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
The libvirt project welcomes contributions in many ways. For most components the best way to contribute is to send patches to the primary development mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
The libvirt project has two primary mailing lists:
- libvirt-users@redhat.com (for user discussions)
- libvir-list@redhat.com (for development only)
Further details on contacting the project are available on the website: