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sysconfig files are owned by the admin of the host. They have the liberty to put anything they want into these files. This makes it difficult to provide different built-in defaults. Remove the sysconfig file and place the current desired default into the service file. Local customizations can now go either into /etc/sysconfig/name or /etc/systemd/system/name.service.d/my-knobs.conf Attempt to handle upgrades in libvirt.spec. Dirty files which are marked as %config will be renamed to file.rpmsave. To restore them automatically, move stale .rpmsave files away, and catch any new rpmsave files in %posttrans. Signed-off-by: Olaf Hering <olaf@aepfle.de> Reviewed-by: Andrea Bolognani <abologna@redhat.com>
298 lines
11 KiB
XML
298 lines
11 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html>
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<html xmlns="http://www.w3.org/1999/xhtml">
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<body>
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<h1 >Remote support</h1>
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<p>
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Libvirt allows you to access hypervisors running on remote
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machines through authenticated and encrypted connections.
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</p>
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<ul id="toc"></ul>
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<h2>
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<a id="Remote_basic_usage">Basic usage</a>
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</h2>
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<p>
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On the remote machine, <code>libvirtd</code> should be running in general.
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See <a href="#Remote_libvirtd_configuration">the section
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on configuring libvirtd</a> for more information.
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</p>
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<p>
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Not all hypervisors supported by libvirt require a running
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<code>libvirtd</code>. If you want to connect to a VMware ESX/ESXi or
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GSX server then <code>libvirtd</code> is not necessary. See the
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<a href="drvesx.html">VMware ESX page</a> for details.
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</p>
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<p>
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To tell libvirt that you want to access a remote resource,
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you should supply a hostname in the normal <a href="uri.html">URI</a> that is passed
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to <code>virConnectOpen</code> (or <code>virsh -c ...</code>).
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For example, if you normally use <code>qemu:///system</code>
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to access the system-wide QEMU daemon, then to access
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the system-wide QEMU daemon on a remote machine called
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<code>compute1.libvirt.org</code> you would use
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<code>qemu://compute1.libvirt.org/system</code>.
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</p>
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<p>
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The <a href="uri.html#URI_remote">section on remote URIs</a>
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describes in more detail these remote URIs.
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</p>
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<p>
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From an API point of view, apart from the change in URI, the
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API should behave the same. For example, ordinary calls
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are routed over the remote connection transparently, and
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values or errors from the remote side are returned to you
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as if they happened locally. Some differences you may notice:
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</p>
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<ul>
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<li> Additional errors can be generated, specifically ones
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relating to failures in the remote transport itself. </li>
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<li> Remote calls are handled synchronously, so they will be
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much slower than, say, direct hypervisor calls. </li>
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</ul>
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<h2>
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<a id="Remote_transports">Transports</a>
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</h2>
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<p>
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Remote libvirt supports a range of transports:
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</p>
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<dl>
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<dt><code>tls</code></dt>
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<dd><a href="https://en.wikipedia.org/wiki/Transport_Layer_Security" title="Transport Layer Security">TLS</a>
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1.0 (SSL 3.1) authenticated and encrypted TCP/IP socket, usually
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listening on a public port number. To use this you will need to
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<a href="tlscerts.html" title="Generating TLS certificates">generate client and
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server certificates</a>.
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The standard port is 16514.
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</dd>
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<dt><code>unix</code></dt>
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<dd> Unix domain socket. Since this is only accessible on the
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local machine, it is not encrypted, and uses Unix permissions or
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SELinux for authentication.
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The standard socket names are
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<code>/var/run/libvirt/libvirt-sock</code> and
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<code>/var/run/libvirt/libvirt-sock-ro</code> (the latter
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for read-only connections).
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</dd>
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<dt><code>ssh</code></dt>
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<dd> Transported over an ordinary
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<a href="https://www.openssh.com/" title="OpenSSH homepage">ssh
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(secure shell)</a> connection.
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Requires <a href="http://netcat.sourceforge.net/">Netcat (nc)</a>
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installed and libvirtd should be running
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on the remote machine. You should use some sort of
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ssh key management (eg.
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<a href="http://mah.everybody.org/docs/ssh" title="Using ssh-agent with ssh">ssh-agent</a>)
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otherwise programs which use
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this transport will stop to ask for a password. </dd>
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<dt><code>ext</code></dt>
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<dd> Any external program which can make a connection to the
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remote machine by means outside the scope of libvirt. </dd>
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<dt><code>tcp</code></dt>
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<dd> Unencrypted TCP/IP socket. Not recommended for production
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use, this is normally disabled, but an administrator can enable
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it for testing or use over a trusted network.
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The standard port is 16509. </dd>
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<dt><code>libssh2</code></dt>
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<dd> Transport over the SSH protocol using
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<a href="https://libssh2.org/" title="libssh2 homepage">libssh2</a> instead
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of the OpenSSH binary. This transport uses the libvirt authentication callback for
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all ssh authentication calls and therefore supports keyboard-interactive authentication
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even with graphical management applications. As with the classic ssh transport
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netcat is required on the remote side.</dd>
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<dt><code>libssh</code></dt>
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<dd> Transport over the SSH protocol using
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<a href="https://libssh.org/" title="libssh homepage">libssh</a> instead
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of the OpenSSH binary. This transport uses the libvirt authentication callback for
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all ssh authentication calls and therefore supports keyboard-interactive authentication
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even with graphical management applications. As with the classic ssh transport
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netcat is required on the remote side.</dd>
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</dl>
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<p>
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The choice of transport is determined by the <a href="uri.html#URI_remote">URI scheme</a>,
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with <code>tls</code> as the default if no explicit transport is requested.
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</p>
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<h2>
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<a id="Remote_libvirtd_configuration">libvirtd configuration file</a>
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</h2>
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<p>
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Libvirtd (the remote daemon) is configured from a file called
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<code>/etc/libvirt/libvirtd.conf</code>, or specified on
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the command line using <code>-f filename</code> or
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<code>--config filename</code>.
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</p>
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<p>
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This file should contain lines of the form below.
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Blank lines and comments beginning with <code>#</code> are ignored.
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</p>
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<pre>setting = value</pre>
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<p>The following settings, values and default are:</p>
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<table class="top_table">
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<tr>
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<th> Line </th>
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<th> Default </th>
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<th> Meaning </th>
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</tr>
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<tr>
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<td> listen_tls <i>[0|1]</i> </td>
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<td> 1 (on) </td>
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<td>
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Listen for secure TLS connections on the public TCP/IP port.
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Note: it is also necessary to start the server in listening mode
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by running it with --listen or adding a LIBVIRTD_ARGS="--listen"
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line to /etc/sysconfig/libvirtd.
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</td>
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</tr>
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<tr>
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<td> listen_tcp <i>[0|1]</i> </td>
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<td> 0 (off) </td>
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<td>
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Listen for unencrypted TCP connections on the public TCP/IP port.
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Note: it is also necessary to start the server in listening mode.
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</td>
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</tr>
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<tr>
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<td> tls_port <i>"service"</i> </td>
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<td> "16514" </td>
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<td>
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The port number or service name to listen on for secure TLS connections.
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</td>
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</tr>
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<tr>
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<td> tcp_port <i>"service"</i> </td>
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<td> "16509" </td>
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<td>
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The port number or service name to listen on for unencrypted TCP connections.
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</td>
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</tr>
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<tr>
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<td> unix_sock_group <i>"groupname"</i> </td>
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<td> "root" </td>
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<td>
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The UNIX group to own the UNIX domain socket. If the socket permissions allow
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group access, then applications running under matching group can access the
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socket. Only valid if running as root
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</td>
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</tr>
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<tr>
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<td> unix_sock_ro_perms <i>"octal-perms"</i> </td>
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<td> "0777" </td>
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<td>
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The permissions for the UNIX domain socket for read-only client connections.
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The default allows any user to monitor domains.
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</td>
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</tr>
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<tr>
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<td> unix_sock_rw_perms <i>"octal-perms"</i> </td>
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<td> "0700" </td>
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<td>
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The permissions for the UNIX domain socket for read-write client connections.
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The default allows only root to manage domains.
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</td>
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</tr>
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<tr>
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<td> tls_no_verify_certificate <i>[0|1]</i> </td>
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<td> 0 (certificates are verified) </td>
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<td>
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If set to 1 then if a client certificate check fails, it is not an error.
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</td>
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</tr>
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<tr>
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<td> tls_no_verify_address <i>[0|1]</i> </td>
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<td> 0 (addresses are verified) </td>
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<td>
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If set to 1 then if a client IP address check fails, it is not an error.
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</td>
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</tr>
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<tr>
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<td> key_file <i>"filename"</i> </td>
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<td> "/etc/pki/libvirt/ private/serverkey.pem" </td>
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<td>
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Change the path used to find the server's private key.
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If you set this to an empty string, then no private key is loaded.
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</td>
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</tr>
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<tr>
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<td> cert_file <i>"filename"</i> </td>
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<td> "/etc/pki/libvirt/ servercert.pem" </td>
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<td>
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Change the path used to find the server's certificate.
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If you set this to an empty string, then no certificate is loaded.
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</td>
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</tr>
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<tr>
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<td> ca_file <i>"filename"</i> </td>
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<td> "/etc/pki/CA/cacert.pem" </td>
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<td>
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Change the path used to find the trusted CA certificate.
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If you set this to an empty string, then no trusted CA certificate is loaded.
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</td>
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</tr>
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<tr>
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<td> crl_file <i>"filename"</i> </td>
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<td> (no CRL file is used) </td>
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<td>
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Change the path used to find the CA certificate revocation list (CRL) file.
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If you set this to an empty string, then no CRL is loaded.
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</td>
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</tr>
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<tr>
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<td> tls_allowed_dn_list ["DN1", "DN2"] </td>
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<td> (none - DNs are not checked) </td>
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<td>
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<p>
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Enable an access control list of client certificate Distinguished
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Names (DNs) which can connect to the TLS port on this server.
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</p>
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<p>
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The default is that DNs are not checked.
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</p>
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<p>
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This list may contain wildcards such as <code>"C=GB,ST=London,L=London,O=Libvirt Project,CN=*"</code>
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Any * matches in the string matches any number of consecutive characters,
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like a simplified <code>glob(7)</code>.
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</p>
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<p>
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Note that if this is an empty list, <i>no client can connect</i>.
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</p>
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<p>
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Note also that GnuTLS returns DNs without spaces
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after commas between the fields (and this is what we check against),
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but the <code>openssl x509</code> tool shows spaces.
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</p>
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To make it easy to see the order of the fields in the DN a helper executable
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<code>virt-pki-query-dn</code> is provided for this particular use case.
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<p>
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</p>
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</td>
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</tr>
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</table>
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<h2>
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<a id="Remote_IPv6">IPv6 support</a>
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</h2>
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<p>
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The libvirtd service and libvirt remote client driver both use the
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<code>getaddrinfo()</code> functions for name resolution and are
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thus fully IPv6 enabled. ie, if a server has IPv6 address configured
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the daemon will listen for incoming connections on both IPv4 and IPv6
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protocols. If a client has an IPv6 address configured and the DNS
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address resolved for a service is reachable over IPv6, then an IPv6
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connection will be made, otherwise IPv4 will be used. In summary it
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should just 'do the right thing(tm)'.
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</p>
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<h2>
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<a id="Remote_limitations">Limitations</a>
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</h2>
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<ul>
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<li> Fine-grained authentication: libvirt in general,
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but in particular the remote case should support more
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fine-grained authentication for operations, rather than
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just read-write/read-only as at present.
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</li>
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</ul>
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<p>
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Please come and discuss these issues and more on <a href="https://www.redhat.com/mailman/listinfo/libvir-list" title="libvir-list mailing list">the mailing list</a>.
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</p>
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</body>
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</html>
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