ae9e6c2a2b
Allow format probing to work around lazy clients which did not specify their format in the overlay. Format probing will be allowed only, if we are able to probe the image, the probing result was successful and the probed image does not have any backing or data file. This relaxes the restrictions which were imposed in commit 3615e8b39bad in cases when we know that the image probing will not result in security issues or data corruption. We perform the image format detection and in the case that we were able to probe the format and the format does not specify a backing store (or doesn't support backing store) we can use this format. With pre-blockdev configurations this will restore the previous behaviour for the images mentioned above as qemu would probe the format anyways. It also improves error reporting compared to the old state as we now report that the backing chain will be broken in case when there is a backing file. In blockdev configurations this ensures that libvirt will not cause data corruption by ending the chain prematurely without notifying the user, but still allows the old semantics when the users forgot to specify the format. Users thus don't have to re-invent when image format detection is safe to do. The price for this is that libvirt will need to keep the image format detector still current and working or replace it by invocation of qemu-img. Signed-off-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@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
Libvirt uses the GNU Autotools build system, so in general can be built and installed with the usual commands, however, we mandate to have the build directory different than the source directory. For example, to build in a manner that is suitable for installing as root, use:
$ mkdir build && cd build
$ ../configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ mkdir build && cd build
$ ../configure --prefix=$HOME/usr
$ make
$ make install
The libvirt code relies on a large number of 3rd party libraries. These will
be detected during execution of the configure script and a summary printed
which lists any missing (optional) dependencies.
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: