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We want to make sure that, at any given time, we have either the modular daemons or the monolithic one running, never both. In order to achieve that, make every single modular unit conflict with the corresponding libvirtd unit. We set both Conflicts=libvirtd.unit and After=libvirtd.unit: this tells systemd that, whenever virtfood.unit and libvirtd.unit are part of the same transaction, the former should win out. Thanks to this, if both the modular daemons and the monolithic one have been enabled because of outdated automation or a simple mistake of the administrator, the request to start libvirtd at boot will be ignored and the result will be a regular modular deployment. If the request to start libvirtd is made when the modular daemons are already running, we have no way to prevent systemd from complying with that request; however, thanks to the way the conflict relationship has been declared, they will be shut down cleanly before libvirtd is started. From the user's point of view, the transition from modular to monolithic will be completely transparent: it's basically the same scenario as a regular package upgrade, just with an extra twist. Note that, while switching from modular to monolithic at runtime happens automatically, going back requires manual intervention, i.e. starting all the necessary sockets one by one. That's okay: the goal here is to prevent misconfiguration and force of habit to accidentally disrupt a working setup, not to encourage the scenario. In a correctly configured and managed host, it should never occur. Signed-off-by: Andrea Bolognani <abologna@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
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: