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Since we are at a transition period where some users may be running monolithic libvirtd and others already the modular topology we need a section that allows users to figure out which is in use. This will be particularly important in the document about enabling logging, as the active log file depends on which daemon is in use. Signed-off-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Erik Skultety <eskultet@redhat.com>
762 lines
33 KiB
ReStructuredText
762 lines
33 KiB
ReStructuredText
===============
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Libvirt Daemons
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===============
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.. contents::
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A libvirt deployment for accessing one of the stateful drivers will require
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one or more daemons to be deployed on the virtualization host. There are a
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number of ways the daemons can be configured which will be outlined in this
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page.
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Architectural options
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=====================
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Monolithic vs modular daemons
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-----------------------------
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Traditionally libvirt provided a single monolithic daemon called ``libvirtd``
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which exposed support for all the stateful drivers, both primary hypervisor
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drivers and secondary supporting drivers. It also enables secure remote access
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from clients running off host.
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Work is underway for the monolithic daemon to be replaced by a new set of
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modular daemons ``virt${DRIVER}d``, each one servicing a single stateful
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driver. A further ``virtproxyd`` daemon will provide secure remote access, as
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well as backcompatibility for clients using the UNIX socket path of the
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monolithic daemon.
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The change to modular daemons should not affect API functionality used by
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management applications. It will, however, have an impact on host provisioning
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tools since there are new systemd services and configuration files to be
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managed.
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Currently both monolithic and modular daemons are built by default, but the RPC
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client still prefers connecting to the monolithic daemon. It is intended to
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switch the RPC client to prefer the modular daemons in the near future. At
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least 1 year after this switch (but not more than 2 years), the monolithic
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daemon will be deleted entirely.
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Operating modes
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---------------
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The libvirt daemons, whether monolithic or modular, can often operate in two
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modes
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* *System mode* - the daemon is running as the root user account, enabling
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access to its full range of functionality. A read-write connection to
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daemons in system mode **typically implies privileges equivalent to having
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a root shell**. Suitable `authentication mechanisms <auth.html>`__ **must
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be enabled** to secure it against untrustworthy clients/users.
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* *Session mode* - the daemon is running as any non-root user account,
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providing access to a more restricted range of functionality. Only client
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apps/users running under **the same UID are permitted to connect**, thus a
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connection does not imply any elevation of privileges.
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Not all drivers support session mode and as such the corresponding
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modular daemon may not support running in this mode
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Monolithic driver daemon
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========================
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The monolithic daemon is known as ``libvirtd`` and has historically been the
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default in libvirt. It is configured via the file ``/etc/libvirt/libvirtd.conf``
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Monolithic sockets
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------------------
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When running in system mode, ``libvirtd`` exposes three UNIX domain sockets, and
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optionally, one or two TCP sockets:
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* ``/var/run/libvirt/libvirt-sock`` - the primary socket for accessing libvirt
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APIs, with full read-write privileges. A connection to this socket gives the
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client privileges that are equivalent to having a root shell. This is the
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socket that most management applications connect to by default.
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* ``/var/run/libvirt/libvirt-sock-ro`` - the secondary socket for accessing
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libvirt APIs, with limited read-only privileges. A connection to this socket
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gives the ability to query the existence of objects and monitor some aspects
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of their operation. This is the socket that most management applications
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connect to when requesting read only mode. Typically this is what a
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monitoring app would use.
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* ``/var/run/libvirt/libvirt-admin-sock`` - the administrative socket for
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controlling operation of the daemon itself (as opposed to drivers it is
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running). This can be used to dynamically reconfigure some aspects of the
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daemon and monitor/control connected clients.
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* ``TCP 16509`` - the non-TLS socket for remotely accessing the libvirt APIs,
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with full read-write privileges. A connection to this socket gives the
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client privileges that are equivalent to having a root shell. Since it does
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not use TLS, an `authentication mechanism <auth.html>`__ that provides
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encryption must be used. Only the GSSAPI/Kerberos mechanism is capable of
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satisfying this requirement. In general applications should not use this
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socket except for debugging in a development/test environment.
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* ``TCP 16514`` - the TLS socket for remotely accessing the libvirt APIs,
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with full read-write privileges. A connection to this socket gives the
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client privileges that are equivalent to having a root shell. Access control
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can be enforced either through validation of `x509 certificates
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<tlscerts.html>`__, and/or by enabling an `authentication mechanism
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<auth.html>`__.
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NB, some distros will use ``/run`` instead of ``/var/run``.
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When running in session mode, ``libvirtd`` exposes two UNIX domain sockets:
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* ``$XDG_RUNTIME_DIR/libvirt/libvirt-sock`` - the primary socket for accessing
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libvirt APIs, with full read-write privileges. A connection to this socket
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does not alter the privileges that the client already has. This is the
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socket that most management applications connect to by default.
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* ``$XDG_RUNTIME_DIR/libvirt/libvirt-admin-sock`` - the administrative socket
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for controlling operation of the daemon itself (as opposed to drivers it is
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running). This can be used to dynamically reconfigure some aspects of the
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daemon and monitor/control connected clients.
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Notice that the session mode does not have a separate read-only socket. Since
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the clients must be running as the same user as the daemon itself, there is
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not any security benefit from attempting to enforce a read-only mode.
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``$XDG_RUNTIME_DIR`` commonly points to a per-user private location on tmpfs,
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such as ``/run/user/$UID``.
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Monolithic Systemd Integration
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------------------------------
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When the ``libvirtd`` daemon is managed by ``systemd`` a number of desirable
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features are available, most notably socket activation.
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Libvirt ships a number of unit files for controlling ``libvirtd``:
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* ``libvirtd.service`` - the main unit file for launching the ``libvirtd``
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daemon in system mode. The command line arguments passed can be configured by
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editing ``/etc/sysconfig/libvirtd``. This is typically only needed to control
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the use of the auto shutdown timeout value. It is recommended that this
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service unit be configured to start on boot. This is because various
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libvirt drivers support autostart of their objects. If it is known that
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autostart is not required, this unit can be left to start on demand.
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* ``libvirtd.socket`` - the unit file corresponding to the main read-write
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UNIX socket ``/var/run/libvirt/libvirt-sock``. This socket is recommended to
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be started on boot by default.
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* ``libvirtd-ro.socket`` - the unit file corresponding to the main read-only
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UNIX socket ``/var/run/libvirt/libvirt-sock-ro``. This socket is recommended
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to be started on boot by default.
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* ``libvirtd-admin.socket`` - the unit file corresponding to the administrative
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UNIX socket ``/var/run/libvirt/libvirt-admin-sock``. This socket is
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recommended to be started on boot by default.
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* ``libvirtd-tcp.socket`` - the unit file corresponding to the TCP 16509 port
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for non-TLS remote access. This socket should not be configured to start on
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boot until the administrator has configured a suitable authentication
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mechanism.
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* ``libvirtd-tls.socket`` - the unit file corresponding to the TCP 16509 port
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for TLS remote access. This socket should not be configured to start on boot
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until the administrator has deployed x509 certificates and optionally
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configured a suitable authentication mechanism.
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NB, some distros will use ``/etc/default`` instead of ``/etc/sysconfig``.
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The socket unit files are newly introduced in 5.6.0. On newly installed hosts
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the UNIX socket units should be enabled by default. When upgrading an existing
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host from a previous version of libvirt, the socket unit files will be masked
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if ``libvirtd`` is currently configured to use the ``--listen`` argument, since
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the ``--listen`` argument is mutually exclusive with use of socket activation.
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When systemd socket activation is used a number of configuration settings in
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``libvirtd.conf`` are no longer honoured. Instead these settings must be
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controlled via the system unit files
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* ``listen_tcp`` - TCP socket usage is enabled by starting the
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``libvirtd-tcp.socket`` unit file.
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* ``listen_tls`` - TLS socket usage is enabled by starting the
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``libvirtd-tls.socket`` unit file.
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* ``tcp_port`` - Port for the non-TLS TCP socket, controlled via the
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``ListenStream`` parameter in the ``libvirtd-tcp.socket`` unit file.
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* ``tls_port`` - Port for the TLS TCP socket, controlled via the
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``ListenStream`` parameter in the ``libvirtd-tls.socket`` unit file.
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* ``listen_addr`` - IP address to listen on, independently controlled via the
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``ListenStream`` parameter in the ``libvirtd-tcp.socket`` or
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``libvirtd-tls.socket`` unit files.
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* ``unix_sock_group`` - UNIX socket group owner, controlled via the
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``SocketGroup`` parameter in the ``libvirtd.socket`` and
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``libvirtd-ro.socket`` unit files
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* ``unix_sock_ro_perms`` - read-only UNIX socket permissions, controlled via the
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``SocketMode`` parameter in the ``libvirtd-ro.socket`` unit file
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* ``unix_sock_rw_perms`` - read-write UNIX socket permissions, controlled via
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the ``SocketMode`` parameter in the ``libvirtd.socket`` unit file
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* ``unix_sock_admin_perms`` - admin UNIX socket permissions, controlled via the
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``SocketMode`` parameter in the ``libvirtd-admin.socket`` unit file
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* ``unix_sock_dir`` - directory in which all UNIX sockets are created
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independently controlled via the ``ListenStream`` parameter in any of the
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``libvirtd.socket``, ``libvirtd-ro.socket`` and ``libvirtd-admin.socket`` unit
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files.
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Systemd releases prior to version 227 lacked support for passing the activation
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socket unit names into the service. When using these old versions, the
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``tcp_port``, ``tls_port`` and ``unix_sock_dir`` settings in ``libvirtd.conf``
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must be changed in lock-step with the equivalent settings in the unit files to
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ensure that ``libvirtd`` can identify the sockets.
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Modular driver daemons
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======================
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The modular daemons are named after the driver which they are running, with
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the pattern ``virt${DRIVER}d`` and will become the default in future libvirt.
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They are configured via the files ``/etc/libvirt/virt${DRIVER}d.conf``
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The following modular daemons currently exist for hypervisor drivers
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* ``virtqemud`` - the QEMU management daemon, for running virtual machines
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on UNIX platforms, optionally with KVM acceleration, in either system or
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session mode
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* ``virtxend`` - the Xen management daemon, for running virtual machines
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on the Xen hypervisor, in system mode only
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* ``virtlxcd`` - the Linux Container management daemon, for running LXC guests
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in system mode only
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* ``virtbhyved`` - the BHyve management daemon, for running virtual machines
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on FreeBSD with the BHyve hypervisor, in system mode.
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* ``virtvboxd`` - the VirtualBox management daemon, for running virtual machines
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on UNIX platforms.
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The additional modular daemons service secondary drivers
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* ``virtinterfaced`` - the host NIC management daemon, in system mode only
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* ``virtnetworkd`` - the virtual network management daemon, in system mode only
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* ``virtnodedevd`` - the host physical device management daemon, in system mode
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only
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* ``virtnwfilterd`` - the host firewall management daemon, in system mode only
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* ``virtsecretd`` - the host secret management daemon, in system or session mode
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* ``virtstoraged`` - the host storage management daemon, in system or session
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mode
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Modular Sockets
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---------------
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When running in system mode, ``virt${DRIVER}d`` exposes three UNIX domain
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sockets:
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* ``/var/run/libvirt/virt${DRIVER}d-sock`` - the primary socket for accessing
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libvirt APIs, with full read-write privileges. For many of the daemons, a
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connection to this socket gives the client privileges that are equivalent to
|
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having a root shell. This is the socket that most management applications
|
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connect to by default.
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* ``/var/run/libvirt/virt${DRIVER}d-sock-ro`` - the secondary socket for
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accessing libvirt APIs, with limited read-only privileges. A connection to
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this socket gives the ability to query the existence of objects and monitor
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some aspects of their operation. This is the socket that most management
|
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applications connect to when requesting read only mode. Typically this is
|
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what a monitoring app would use.
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* ``/var/run/libvirt/virt${DRIVER}d-admin-sock`` - the administrative socket for
|
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controlling operation of the daemon itself (as opposed to drivers it is
|
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running). This can be used to dynamically reconfigure some aspects of the
|
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daemon and monitor/control connected clients.
|
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NB, some distros will use ``/run`` instead of ``/var/run``.
|
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When running in session mode, ``virt${DRIVER}d`` exposes two UNIX domain sockets:
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* ``$XDG_RUNTIME_DIR/libvirt/virt${DRIVER}d-sock`` - the primary socket for
|
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accessing libvirt APIs, with full read-write privileges. A connection to this
|
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socket does not alter the privileges that the client already has. This is the
|
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socket that most management applications connect to by default.
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* ``$XDG_RUNTIME_DIR/libvirt/virt${DRIVER}d-admin-sock`` - the administrative
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socket for controlling operation of the daemon itself (as opposed to drivers
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it is running). This can be used to dynamically reconfigure some aspects of
|
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the daemon and monitor/control connected clients.
|
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|
|
Notice that the session mode does not have a separate read-only socket. Since
|
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the clients must be running as the same user as the daemon itself, there is
|
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not any security benefit from attempting to enforce a read-only mode.
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``$XDG_RUNTIME_DIR`` commonly points to a per-user private location on tmpfs,
|
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such as ``/run/user/$UID``.
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Modular Systemd Integration
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---------------------------
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|
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When the ``virt${DRIVER}d`` daemon is managed by ``systemd`` a number of
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desirable features are available, most notably socket activation.
|
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|
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Libvirt ships a number of unit files for controlling ``virt${DRIVER}d``:
|
|
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* ``virt${DRIVER}d.service`` - the main unit file for launching the
|
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``virt${DRIVER}d`` daemon in system mode. The command line arguments passed
|
|
can be configured by editing ``/etc/sysconfig/virt${DRIVER}d``. This is
|
|
typically only needed to control the use of the auto shutdown timeout value.
|
|
It is recommended that this service unit be configured to start on boot.
|
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This is because various libvirt drivers support autostart of their objects.
|
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If it is known that autostart is not required, this unit can be left to start
|
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on demand.
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* ``virt${DRIVER}d.socket`` - the unit file corresponding to the main read-write
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UNIX socket ``/var/run/libvirt/virt${DRIVER}d-sock``. This socket is
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recommended to be started on boot by default.
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* ``virt${DRIVER}d-ro.socket`` - the unit file corresponding to the main
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read-only UNIX socket ``/var/run/libvirt/virt${DRIVER}d-sock-ro``. This
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socket is recommended to be started on boot by default.
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* ``virt${DRIVER}d-admin.socket`` - the unit file corresponding to the
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administrative UNIX socket ``/var/run/libvirt/virt${DRIVER}d-admin-sock``.
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This socket is recommended to be started on boot by default.
|
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NB, some distros will use ``/etc/default`` instead of ``/etc/sysconfig``.
|
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The socket unit files are newly introduced in 5.6.0. On newly installed hosts
|
|
the UNIX socket units should be enabled by default. When upgrading an existing
|
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host from a previous version of libvirt, the socket unit files will be masked
|
|
if ``virt${DRIVER}d`` is currently configured to use the ``--listen`` argument,
|
|
since the ``--listen`` argument is mutually exclusive with use of socket
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activation.
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When systemd socket activation is used a number of configuration settings in
|
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``virt${DRIVER}d.conf`` are no longer honoured. Instead these settings must be
|
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controlled via the system unit files:
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|
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* ``unix_sock_group`` - UNIX socket group owner, controlled via the
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``SocketGroup`` parameter in the ``virt${DRIVER}d.socket`` and
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``virt${DRIVER}d-ro.socket`` unit files
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* ``unix_sock_ro_perms`` - read-only UNIX socket permissions, controlled via the
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``SocketMode`` parameter in the ``virt${DRIVER}d-ro.socket`` unit file
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* ``unix_sock_rw_perms`` - read-write UNIX socket permissions, controlled via
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the ``SocketMode`` parameter in the ``virt${DRIVER}d.socket`` unit file
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* ``unix_sock_admin_perms`` - admin UNIX socket permissions, controlled via the
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``SocketMode`` parameter in the ``virt${DRIVER}d-admin.socket`` unit file
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* ``unix_sock_dir`` - directory in which all UNIX sockets are created
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independently controlled via the ``ListenStream`` parameter in any of the
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``virt${DRIVER}d.socket``, ``virt${DRIVER}d-ro.socket`` and
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``virt${DRIVER}d-admin.socket`` unit files.
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|
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Systemd releases prior to version 227 lacked support for passing the activation
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socket unit names into the service. When using these old versions, the
|
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``unix_sock_dir`` setting in ``virt${DRIVER}d.conf`` must be changed in
|
|
lock-step with the equivalent setting in the unit files to ensure that
|
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``virt${DRIVER}d`` can identify the sockets.
|
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|
|
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Switching to modular daemons
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----------------------------
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If a host is currently set to use the monolithic ``libvirtd`` daemon and needs
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to be migrated to the modular daemons a number of services need to be
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changed. The steps below outline the process on hosts using the systemd init
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service.
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While it is technically possible to do this while virtual machines are running,
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it is recommended that virtual machines be stopped or live migrated to a new
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host first.
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#. Stop the current monolithic daemon and its socket units
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::
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$ systemctl stop libvirtd.service
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$ systemctl stop libvirtd{,-ro,-admin,-tcp,-tls}.socket
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#. Disable future start of the monolithic daemon
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::
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$ systemctl disable libvirtd.service
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$ systemctl disable libvirtd{,-ro,-admin,-tcp,-tls}.socket
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For stronger protection it is valid to use ``mask`` instead of ``disable``
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too.
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#. Enable the new daemons for the particular virtualizationd driver desired,
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and any of the secondary drivers to accompany it. The following example
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enables the QEMU driver and all the secondary drivers:
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::
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$ for drv in qemu interface network nodedev nwfilter secret storage
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do
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systemctl unmask virt${drv}d.service
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systemctl unmask virt${drv}d{,-ro,-admin}.socket
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systemctl enable virt${drv}d.service
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systemctl enable virt${drv}d{,-ro,-admin}.socket
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done
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#. Start the sockets for the same set of daemons. There is no need to start the
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services as they will get started when the first socket connection is
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established
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::
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$ for drv in qemu network nodedev nwfilter secret storage
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do
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systemctl start virt${drv}d{,-ro,-admin}.socket
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done
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#. If connections from remote hosts need to be supported the proxy daemon
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must be enabled and started
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::
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$ systemctl unmask virtproxyd.service
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$ systemctl unmask virtproxyd{,-ro,-admin}.socket
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$ systemctl enable virtproxyd.service
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$ systemctl enable virtproxyd{,-ro,-admin}.socket
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$ systemctl start virtproxyd{,-ro,-admin}.socket
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The UNIX sockets allow for remote access using SSH tunneling. If ``libvirtd``
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had TCP or TLS sockets configured, those should be started too
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::
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$ systemctl unmask virtproxyd-tls.socket
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$ systemctl enable virtproxyd-tls.socket
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$ systemctl start virtproxyd-tls.socket
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Checking whether modular/monolithic mode is in use
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==================================================
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New distributions are likely to use the modular mode although the upgrade
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process preserves whichever mode was in use before the upgrade.
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To determine whether modular or monolithic mode is in use on a host running
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``systemd`` as the init system you can take the following steps:
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#. Check whether the modular daemon infrastructure is in use
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First check whether the modular daemon you are interested (see
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`Modular driver daemons`_ for a summary of which daemons are provided by
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libvirt) in is running:
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|
|
#. Check ``.socket`` for socket activated services
|
|
|
|
::
|
|
|
|
# systemctl is-active virtqemud.socket
|
|
active
|
|
|
|
#. Check ``.service`` for always-running daemons
|
|
|
|
::
|
|
|
|
# systemctl is-active virtqemud.service
|
|
active
|
|
|
|
If either of the above is ``active`` your system is using the modular daemons.
|
|
|
|
#. Check whether the monolithic daemon is in use
|
|
|
|
#. Check ``libvirtd.socket``
|
|
|
|
::
|
|
|
|
# systemctl is-active libvirtd.socket
|
|
active
|
|
|
|
#. Check ``libvirtd.service`` for always-running daemon
|
|
|
|
::
|
|
|
|
# systemctl is-active libvirtd.service
|
|
active
|
|
|
|
If either of the above is ``active`` your system is using the monolithic
|
|
daemon.
|
|
|
|
#. To determine which of the above will be in use on the next boot of the system,
|
|
substitute ``is-enabled`` for ``is-active`` in the above examples.
|
|
|
|
Proxy daemon
|
|
============
|
|
|
|
Proxy sockets
|
|
-------------
|
|
|
|
When running in system mode, ``virtproxyd`` exposes three UNIX domain sockets,
|
|
and optionally, one or two TCP sockets. These sockets are identical to those
|
|
provided by the traditional ``libvirtd`` so refer to earlier documentation in
|
|
this page.
|
|
|
|
When running in session mode, ``virtproxyd`` exposes two UNIX domain sockets,
|
|
which are again identical to those provided by ``libvirtd``.
|
|
|
|
Proxy Systemd Integration
|
|
-------------------------
|
|
|
|
When the ``virtproxyd`` daemon is managed by ``systemd`` a number of desirable
|
|
features are available, most notably socket activation.
|
|
|
|
Libvirt ships a number of unit files for controlling ``virtproxyd``:
|
|
|
|
* ``virtproxyd.service`` - the main unit file for launching the ``virtproxyd``
|
|
daemon in system mode. The command line arguments passed can be configured by
|
|
editing ``/etc/sysconfig/virtproxyd``. This is typically only needed to
|
|
control the use of the auto shutdown timeout value.
|
|
|
|
* ``virtproxyd.socket`` - the unit file corresponding to the main read-write
|
|
UNIX socket ``/var/run/libvirt/libvirt-sock``. This socket is recommended to
|
|
be started on boot by default.
|
|
|
|
* ``virtproxyd-ro.socket`` - the unit file corresponding to the main read-only
|
|
UNIX socket ``/var/run/libvirt/libvirt-sock-ro``. This socket is recommended
|
|
to be started on boot by default.
|
|
|
|
* ``virtproxyd-admin.socket`` - the unit file corresponding to the
|
|
administrative UNIX socket ``/var/run/libvirt/libvirt-admin-sock``. This
|
|
socket is recommended to be started on boot by default.
|
|
|
|
* ``virtproxyd-tcp.socket`` - the unit file corresponding to the TCP 16509 port
|
|
for non-TLS remote access. This socket should not be configured to start on
|
|
boot until the administrator has configured a suitable authentication
|
|
mechanism.
|
|
|
|
* ``virtproxyd-tls.socket`` - the unit file corresponding to the TCP 16509 port
|
|
for TLS remote access. This socket should not be configured to start on boot
|
|
until the administrator has deployed x509 certificates and optionally
|
|
configured a suitable authentication mechanism.
|
|
|
|
NB, some distros will use ``/etc/default`` instead of ``/etc/sysconfig``.
|
|
|
|
The socket unit files are newly introduced in 5.6.0. On newly installed hosts
|
|
the UNIX socket units should be enabled by default. When upgrading an existing
|
|
host from a previous version of libvirt, the socket unit files will be masked
|
|
if ``virtproxyd`` is currently configured to use the ``--listen`` argument, since
|
|
the ``--listen`` argument is mutually exclusive with use of socket activation.
|
|
|
|
When systemd socket activation is used a number of configuration settings in
|
|
``virtproxyd.conf`` are no longer honoured. Instead these settings must be
|
|
controlled via the system unit files. Refer to the earlier documentation on
|
|
the ``libvirtd`` service socket configuration for further information.
|
|
|
|
|
|
Logging daemon
|
|
==============
|
|
|
|
The ``virtlogd`` daemon provides a service for managing log files associated
|
|
with QEMU virtual machines. The QEMU process is given one or more pipes, the
|
|
other end of which are owned by the ``virtlogd`` daemon. It will then write
|
|
data on those pipes to log files, while enforcing a maximum file size and
|
|
performing log rollover at the size limit.
|
|
|
|
Since the daemon holds open anonymous pipe file descriptors, it must never be
|
|
stopped while any QEMU virtual machines are running. To enable software updates
|
|
to be applied, the daemon is capable of re-executing itself while keeping all
|
|
file descriptors open. This can be triggered by sending the daemon ``SIGUSR1``
|
|
|
|
Logging Sockets
|
|
---------------
|
|
|
|
When running in system mode, ``virtlogd`` exposes two UNIX domain sockets:
|
|
|
|
* ``/var/run/libvirt/virtlogd-sock`` - the primary socket for accessing
|
|
libvirt APIs, with full read-write privileges. Access to the socket is
|
|
restricted to the root user.
|
|
|
|
* ``/var/run/libvirt/virtlogd-admin-sock`` - the administrative socket for
|
|
controlling operation of the daemon itself (as opposed to drivers it is
|
|
running). This can be used to dynamically reconfigure some aspects of the
|
|
daemon and monitor/control connected clients.
|
|
|
|
NB, some distros will use ``/run`` instead of ``/var/run``.
|
|
|
|
When running in session mode, ``virtlogd`` exposes two UNIX domain sockets:
|
|
|
|
* ``$XDG_RUNTIME_DIR/libvirt/virtlogd-sock`` - the primary socket for
|
|
accessing libvirt APIs, with full read-write privileges. Access to the
|
|
socket is restricted to the unprivileged user running the daemon.
|
|
|
|
* ``$XDG_RUNTIME_DIR/libvirt/virtlogd-admin-sock`` - the administrative
|
|
socket for controlling operation of the daemon itself (as opposed to drivers
|
|
it is running). This can be used to dynamically reconfigure some aspects of
|
|
the daemon and monitor/control connected clients.
|
|
|
|
``$XDG_RUNTIME_DIR`` commonly points to a per-user private location on tmpfs,
|
|
such as ``/run/user/$UID``.
|
|
|
|
Logging Systemd Integration
|
|
---------------------------
|
|
|
|
When the ``virtlogd`` daemon is managed by ``systemd`` a number of desirable
|
|
features are available, most notably socket activation.
|
|
|
|
Libvirt ships a number of unit files for controlling ``virtlogd``:
|
|
|
|
* ``virtlogd.service`` - the main unit file for launching the
|
|
``virtlogd`` daemon in system mode. The command line arguments passed
|
|
can be configured by editing ``/etc/sysconfig/virtlogd``. This is
|
|
typically only needed to control the use of the auto shutdown timeout value.
|
|
|
|
* ``virtlogd.socket`` - the unit file corresponding to the main read-write
|
|
UNIX socket ``/var/run/libvirt/virtlogd-sock``. This socket is recommended
|
|
to be started on boot by default.
|
|
|
|
* ``virtlogd-admin.socket`` - the unit file corresponding to the administrative
|
|
UNIX socket ``/var/run/libvirt/virtlogd-admin-sock``. This socket is
|
|
recommended to be started on boot by default.
|
|
|
|
NB, some distros will use ``/etc/default`` instead of ``/etc/sysconfig``.
|
|
|
|
When systemd socket activation is used a number of configuration settings in
|
|
``virtlogd.conf`` are no longer honoured. Instead these settings must be
|
|
controlled via the system unit files:
|
|
|
|
* ``unix_sock_group`` - UNIX socket group owner, controlled via the
|
|
``SocketGroup`` parameter in the ``virtlogd.socket`` and
|
|
``virtlogd-ro.socket`` unit files
|
|
|
|
* ``unix_sock_ro_perms`` - read-only UNIX socket permissions, controlled via the
|
|
``SocketMode`` parameter in the ``virtlogd-ro.socket`` unit file
|
|
|
|
* ``unix_sock_rw_perms`` - read-write UNIX socket permissions, controlled via
|
|
the ``SocketMode`` parameter in the ``virtlogd.socket`` unit file
|
|
|
|
* ``unix_sock_admin_perms`` - admin UNIX socket permissions, controlled via the
|
|
``SocketMode`` parameter in the ``virtlogd-admin.socket`` unit file
|
|
|
|
* ``unix_sock_dir`` - directory in which all UNIX sockets are created
|
|
independently controlled via the ``ListenStream`` parameter in any of the
|
|
``virtlogd.socket`` and ``virtlogd-admin.socket`` unit files.
|
|
|
|
Systemd releases prior to version 227 lacked support for passing the activation
|
|
socket unit names into the service. When using these old versions, the
|
|
``unix_sock_dir`` setting in ``virtlogd.conf`` must be changed in
|
|
lock-step with the equivalent setting in the unit files to ensure that
|
|
``virtlogd`` can identify the sockets.
|
|
|
|
Locking daemon
|
|
==============
|
|
|
|
The ``virtlockd`` daemon provides a service for holding locks against file
|
|
images and devices serving as backing storage for virtual disks. The locks
|
|
will be held for as long as there is a QEMU process running with the disk
|
|
open.
|
|
|
|
To ensure continuity of locking, the daemon holds open anonymous file
|
|
descriptors, it must never be stopped while any QEMU virtual machines are
|
|
running. To enable software updates to be applied, the daemon is capable of
|
|
re-executing itself while keeping all file descriptors open. This can be
|
|
triggered by sending the daemon ``SIGUSR1``
|
|
|
|
Locking Sockets
|
|
---------------
|
|
|
|
When running in system mode, ``virtlockd`` exposes two UNIX domain sockets:
|
|
|
|
* ``/var/run/libvirt/virtlockd-sock`` - the primary socket for accessing
|
|
libvirt APIs, with full read-write privileges. Access to the socket is
|
|
restricted to the root user.
|
|
|
|
* ``/var/run/libvirt/virtlockd-admin-sock`` - the administrative socket for
|
|
controlling operation of the daemon itself (as opposed to drivers it is
|
|
running). This can be used to dynamically reconfigure some aspects of the
|
|
daemon and monitor/control connected clients.
|
|
|
|
NB, some distros will use ``/run`` instead of ``/var/run``.
|
|
|
|
When running in session mode, ``virtlockd`` exposes two UNIX domain sockets:
|
|
|
|
* ``$XDG_RUNTIME_DIR/libvirt/virtlockd-sock`` - the primary socket for
|
|
accessing libvirt APIs, with full read-write privileges. Access to the
|
|
socket is restricted to the unprivileged user running the daemon.
|
|
|
|
* ``$XDG_RUNTIME_DIR/libvirt/virtlockd-admin-sock`` - the administrative
|
|
socket for controlling operation of the daemon itself (as opposed to drivers
|
|
it is running). This can be used to dynamically reconfigure some aspects of
|
|
the daemon and monitor/control connected clients.
|
|
|
|
``$XDG_RUNTIME_DIR`` commonly points to a per-user private location on tmpfs,
|
|
such as ``/run/user/$UID``.
|
|
|
|
Locking Systemd Integration
|
|
---------------------------
|
|
|
|
When the ``virtlockd`` daemon is managed by ``systemd`` a number of desirable
|
|
features are available, most notably socket activation.
|
|
|
|
Libvirt ships a number of unit files for controlling ``virtlockd``:
|
|
|
|
* ``virtlockd.service`` - the main unit file for launching the
|
|
``virtlockd`` daemon in system mode. The command line arguments passed
|
|
can be configured by editing ``/etc/sysconfig/virtlockd``. This is
|
|
typically only needed to control the use of the auto shutdown timeout value.
|
|
|
|
* ``virtlockd.socket`` - the unit file corresponding to the main read-write
|
|
UNIX socket ``/var/run/libvirt/virtlockd-sock``. This socket is recommended
|
|
to be started on boot by default.
|
|
|
|
* ``virtlockd-admin.socket`` - the unit file corresponding to the administrative
|
|
UNIX socket ``/var/run/libvirt/virtlockd-admin-sock``. This socket is
|
|
recommended to be started on boot by default.
|
|
|
|
NB, some distros will use ``/etc/default`` instead of ``/etc/sysconfig``.
|
|
|
|
When systemd socket activation is used a number of configuration settings in
|
|
``virtlockd.conf`` are no longer honoured. Instead these settings must be
|
|
controlled via the system unit files:
|
|
|
|
* ``unix_sock_group`` - UNIX socket group owner, controlled via the
|
|
``SocketGroup`` parameter in the ``virtlockd.socket`` and
|
|
``virtlockd-ro.socket`` unit files
|
|
|
|
* ``unix_sock_ro_perms`` - read-only UNIX socket permissions, controlled via the
|
|
``SocketMode`` parameter in the ``virtlockd-ro.socket`` unit file
|
|
|
|
* ``unix_sock_rw_perms`` - read-write UNIX socket permissions, controlled via
|
|
the ``SocketMode`` parameter in the ``virtlockd.socket`` unit file
|
|
|
|
* ``unix_sock_admin_perms`` - admin UNIX socket permissions, controlled via the
|
|
``SocketMode`` parameter in the ``virtlockd-admin.socket`` unit file
|
|
|
|
* ``unix_sock_dir`` - directory in which all UNIX sockets are created
|
|
independently controlled via the ``ListenStream`` parameter in any of the
|
|
``virtlockd.socket`` and ``virtlockd-admin.socket`` unit files.
|
|
|
|
Systemd releases prior to version 227 lacked support for passing the activation
|
|
socket unit names into the service. When using these old versions, the
|
|
``unix_sock_dir`` setting in ``virtlockd.conf`` must be changed in
|
|
lock-step with the equivalent setting in the unit files to ensure that
|
|
``virtlockd`` can identify the sockets.
|
|
|
|
Changing command line options for daemons
|
|
=========================================
|
|
|
|
Two ways exist to override the defaults in the provided service files:
|
|
either a systemd "drop-in" configuration file, or a ``/etc/sysconfig/$daemon``
|
|
file must be created. For example, to change the command line option
|
|
for a debug session of ``libvirtd``, create a file
|
|
``/etc/systemd/system/libvirtd.service.d/debug.conf`` with the following content:
|
|
|
|
::
|
|
|
|
[Unit]
|
|
Description=Virtualization daemon, with override from debug.conf
|
|
|
|
[Service]
|
|
Environment=G_DEBUG=fatal-warnings
|
|
Environment=LIBVIRTD_ARGS="--listen --verbose"
|
|
|
|
After changes to systemd "drop-in" configuration files it is required to run
|
|
``systemctl daemon-reload``.
|