dafef600f4
Due to historical back-compat, bare 'virsh snapshot-create-as' favors internal snapshots (but can't be used on domains with raw storage), while 'virsh snapshot-create-as --disk-only' favors external snapshots. What's more, snapshots created with --disk-only while the domain was running are marked as snapshot state 'disk-snapshot', while snapshots created while the domain was offline are marked as snapshot state 'shutdown' (a 'disk-snapshot' image might not be quiescent, while a 'shutdown' snapshot always is). But this leads to some interesting problems: if we create a --disk-only snapshot of an offline guest, and then immediately try to 'virsh snapshot-create --redefine' using the resulting XML to overwrite the existing snapashot in place, things silently succeed, but 'virsh snapshot-create --redefine --disk-only' fails with an error message that the snapshot state is not 'disk-only'. Worse, if we delete the snapshot metadata first and then try to recreate things, omitting --disk-only fails because the verification code wants to force the default of an internal snapshot (which doesn't work with raw disks), and using --disk-only still fails because the snapshot XML is not 'disk-only' - making it impossible to recreate the snapshot metadata (or to transfer it from one libvirtd host to another). Ideally, the presence or absence of the --disk-only flag, and the presence or absence of an existing snapshot being overwritten, shouldn't matter; if the XML is valid for one situation, it should always be valid to redefine the metadata for that snapshot. Fix things by uniformly using virDomainSnapshotDefIsExternal() (caching the results up front, and eliminating other 'if' clauses now rendered redundant) when deciding whether the XML being requested for redefinition should permit external or force internal state capture (we got it right in only one out of three places in the function). See also https://bugzilla.redhat.com/1680304; this fixes the domain-agnostic problems mentioned there, but another patch is needed to fix further oddities with the qemu driver. I did not check for sure when the problems were introduced (git blame puts some affected hunks as far back as 1.0.0), but it was definitely been broken even before when commit 670e86bf (1.1.4) factored redefine prep out of qemu code into the common snapshot_conf code. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: John Ferlan <jferlan@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 2.1 (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. For example, to build in a manner that is suitable for installing as root, use:
$ ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ ./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: