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< body >
< h1 > Remote support< / h1 >
< p >
Libvirt allows you to access hypervisors running on remote
machines through authenticated and encrypted connections.
< / p >
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< ul id = "toc" > < / ul >
< 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
on configuring libvirtd< / a > for more information.
< / p >
< p >
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Not all hypervisors supported by libvirt require a running
< code > libvirtd< / code > . If you want to connect to a VMware ESX/ESXi or
GSX server then < code > libvirtd< / code > is not necessary. See the
< a href = "drvesx.html" > VMware ESX page< / a > for details.
< / p >
< p >
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To tell libvirt that you want to access a remote resource,
you should supply a hostname in the normal < a href = "uri.html" > URI< / a > that is passed
to < code > virConnectOpen< / code > (or < code > virsh -c ...< / code > ).
For example, if you normally use < code > qemu:///system< / code >
to access the system-wide QEMU daemon, then to access
the system-wide QEMU daemon on a remote machine called
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< code > compute1.libvirt.org< / code > you would use
< code > qemu://compute1.libvirt.org/system< / code > .
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< / p >
< 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.
< / p >
< p >
From an API point of view, apart from the change in URI, the
API should behave the same. For example, ordinary calls
are routed over the remote connection transparently, and
values or errors from the remote side are returned to you
as if they happened locally. Some differences you may notice:
< / p >
< ul >
< li > Additional errors can be generated, specifically ones
relating to failures in the remote transport itself. < / li >
< li > Remote calls are handled synchronously, so they will be
much slower than, say, direct hypervisor calls. < / li >
< / 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 >
Remote libvirt supports a range of transports:
< / p >
< 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
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 > .
The standard port is 16514.
< / 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
local machine, it is not encrypted, and uses Unix permissions or
SELinux for authentication.
The standard socket names are
< code > /var/run/libvirt/libvirt-sock< / code > and
< code > /var/run/libvirt/libvirt-sock-ro< / code > (the latter
for read-only connections).
< / 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.
Requires < a href = "http://netcat.sourceforge.net/" > Netcat (nc)< / a >
installed and libvirtd should be running
on the remote machine. You should use some sort of
ssh key management (eg.
< a href = "http://mah.everybody.org/docs/ssh" title = "Using ssh-agent with ssh" > ssh-agent< / a > )
otherwise programs which use
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
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
use, this is normally disabled, but an administrator can enable
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
all ssh authentication calls and therefore supports keyboard-interactive authentication
even with graphical management applications. As with the classic ssh transport
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netcat is required on the remote side.< / dd >
< dt > < code > libssh< / code > < / dt >
< 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
all ssh authentication calls and therefore supports keyboard-interactive authentication
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 >
< p >
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The choice of transport is determined by the < a href = "uri.html#URI_remote" > URI scheme< / a > ,
with < code > tls< / code > as the default if no explicit transport is requested.
< / 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 >
Libvirtd (the remote daemon) is configured from a file called
< code > /etc/libvirt/libvirtd.conf< / code > , or specified on
the command line using < code > -f filename< / code > or
< code > --config filename< / code > .
< / p >
< p >
This file should contain lines of the form below.
Blank lines and comments beginning with < code > #< / code > are ignored.
< / p >
< pre > setting = value< / pre >
< p > The following settings, values and default are:< / p >
< table class = "top_table" >
< tr >
< th > Line < / th >
< th > Default < / th >
< th > Meaning < / th >
< / tr >
< tr >
< td > listen_tls < i > [0|1]< / i > < / td >
< td > 1 (on) < / td >
< td >
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 by
running it with --listen or editing /etc/sysconfig/libvirtd by uncommenting the LIBVIRTD_ARGS="--listen" line
to cause the server to come up in listening mode whenever it is started.
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< / td >
< / tr >
< tr >
< td > listen_tcp < i > [0|1]< / i > < / td >
< td > 0 (off) < / td >
< td >
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 >
< / tr >
< tr >
< td > tls_port < i > "service"< / i > < / td >
< td > "16514" < / td >
< td >
The port number or service name to listen on for secure TLS connections.
< / td >
< / tr >
< tr >
< td > tcp_port < i > "service"< / i > < / td >
< td > "16509" < / td >
< td >
The port number or service name to listen on for unencrypted TCP connections.
< / td >
< / tr >
< tr >
< td > unix_sock_group < i > "groupname"< / i > < / td >
< td > "root" < / td >
< td >
The UNIX group to own the UNIX domain socket. If the socket permissions allow
group access, then applications running under matching group can access the
socket. Only valid if running as root
< / td >
< / tr >
< tr >
< td > unix_sock_ro_perms < i > "octal-perms"< / i > < / td >
< td > "0777" < / td >
< td >
The permissions for the UNIX domain socket for read-only client connections.
The default allows any user to monitor domains.
< / td >
< / tr >
< tr >
< td > unix_sock_rw_perms < i > "octal-perms"< / i > < / td >
< td > "0700" < / td >
< td >
The permissions for the UNIX domain socket for read-write client connections.
The default allows only root to manage domains.
< / td >
< / tr >
< tr >
< td > tls_no_verify_certificate < i > [0|1]< / i > < / td >
< td > 0 (certificates are verified) < / td >
< td >
If set to 1 then if a client certificate check fails, it is not an error.
< / td >
< / tr >
< tr >
< td > tls_no_verify_address < i > [0|1]< / i > < / td >
< td > 0 (addresses are verified) < / td >
< td >
If set to 1 then if a client IP address check fails, it is not an error.
< / td >
< / tr >
< tr >
< td > key_file < i > "filename"< / i > < / td >
< td > "/etc/pki/libvirt/ private/serverkey.pem" < / td >
< td >
Change the path used to find the server's private key.
If you set this to an empty string, then no private key is loaded.
< / td >
< / tr >
< tr >
< td > cert_file < i > "filename"< / i > < / td >
< td > "/etc/pki/libvirt/ servercert.pem" < / td >
< td >
Change the path used to find the server's certificate.
If you set this to an empty string, then no certificate is loaded.
< / td >
< / tr >
< tr >
< td > ca_file < i > "filename"< / i > < / td >
< td > "/etc/pki/CA/cacert.pem" < / td >
< td >
Change the path used to find the trusted CA certificate.
If you set this to an empty string, then no trusted CA certificate is loaded.
< / td >
< / tr >
< tr >
< td > crl_file < i > "filename"< / i > < / td >
< td > (no CRL file is used) < / td >
< td >
Change the path used to find the CA certificate revocation list (CRL) file.
If you set this to an empty string, then no CRL is loaded.
< / td >
< / tr >
< tr >
< td > tls_allowed_dn_list ["DN1", "DN2"] < / td >
< td > (none - DNs are not checked) < / td >
< td >
< p >
Enable an access control list of client certificate Distinguished
Names (DNs) which can connect to the TLS port on this server.
< / p >
< p >
The default is that DNs are not checked.
< / p >
< 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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See the POSIX < code > fnmatch< / code > function for the format
of the wildcards.
< / p >
< p >
Note that if this is an empty list, < i > no client can connect< / i > .
< / p >
< p >
Note also that GnuTLS returns DNs without spaces
after commas between the fields (and this is what we check against),
but the < code > openssl x509< / code > tool shows spaces.
< / p >
< / td >
< / tr >
< / 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 >
The libvirtd service and libvirt remote client driver both use the
< code > getaddrinfo()< / code > functions for name resolution and are
thus fully IPv6 enabled. ie, if a server has IPv6 address configured
the daemon will listen for incoming connections on both IPv4 and IPv6
protocols. If a client has an IPv6 address configured and the DNS
address resolved for a service is reachable over IPv6, then an IPv6
connection will be made, otherwise IPv4 will be used. In summary it
should just 'do the right thing(tm)'.
< / 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 >
< li > Fine-grained authentication: libvirt in general,
but in particular the remote case should support more
fine-grained authentication for operations, rather than
just read-write/read-only as at present.
< / li >
< / ul >
< p >
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 > .
< / p >
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