23.3. Transport modes
libvirt supports the following transport modes:
Transport Layer Security TLS 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 generate client and server certificates. The standard port is 16514.
Unix domain sockets are only accessible on the local machine. Sockets are not encrypted, and use UNIX permissions or SELinux for authentication. The standard socket names are /var/run/libvirt/libvirt-sock and /var/run/libvirt/libvirt-sock-ro (for read-only connections).
Transported over a Secure Shell protocol (SSH) connection. Requires Netcat (the nc package) installed. The libvirt daemon (libvirtd) must be running on the remote machine. Port 22 must be open for SSH access. You should use some sort of ssh key management (for example, the ssh-agent utility) or you will be prompted for a password.
The ext parameter is used for any external program which can make a connection to the remote machine by means outside the scope of libvirt. This parameter is unsupported.
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. The default port is 16509.
A Uniform Resource Identifier (URI) is used by virsh and libvirt to connect to a remote host. URIs can also be used with the --connect parameter for the virsh command to execute single commands or migrations on remote hosts.
driver[+transport]://[username@][hostname][:port]/[path][?extraparameters]
Examples of remote management parameters
- Connect to a remote Xen hypervisor on the host named
towada, using SSH transport and the SSH usernameccurran.xen+ssh://ccurran@towada/
- Connect to a remote Xen hypervisor on the host named
towadausing TLS.xen://towada/
- Connect to a remote Xen hypervisor on host
towadausing TLS. Theno_verify=1tells libvirt not to verify the server's certificate.xen://towada/?no_verify=1
- Connect to a remote KVM hypervisor on host
towadausing SSH.qemu+ssh://towada/system
Testing examples
- Connect to the local KVM hypervisor with a non-standard UNIX socket. The full path to the Unix socket is supplied explicitly in this case.
qemu+unix:///system?socket=/opt/libvirt/run/libvirt/libvirt-sock
- Connect to the libvirt daemon with an unencrypted TCP/IP connection to the server with the IP address 10.1.1.10 on port 5000. This uses the test driver with default settings.
test+tcp://10.1.1.10:5000/default
Extra parameters can be appended to remote URIs. The table below Table 23.1, “Extra URI parameters” covers the recognized parameters. All other parameters are ignored. Note that parameter values must be URI-escaped (that is, a question mark (?) is appended before the parameter and special characters are converted into the URI format).
| Name | Transport mode | Description | Example usage |
|---|---|---|---|
| name | all modes | The name passed to the remote virConnectOpen function. The name is normally formed by removing transport, hostname, port number, username and extra parameters from the remote URI, but in certain very complex cases it may be better to supply the name explicitly. | name=qemu:///system |
| command | ssh and ext | The external command. For ext transport this is required. For ssh the default is ssh. The PATH is searched for the command. | command=/opt/openssh/bin/ssh |
| socket | unix and ssh | The path to the UNIX domain socket, which overrides the default. For ssh transport, this is passed to the remote netcat command (see netcat). | socket=/opt/libvirt/run/libvirt/libvirt-sock |
| netcat | ssh |
The
netcat command can be used to connect to remote systems. The default netcat parameter uses the nc command. For SSH transport, libvirt constructs an SSH command using the form below:
The
port, username and hostname parameters can be specified as part of the remote URI. The command, netcat and socket come from other extra parameters.
| netcat=/opt/netcat/bin/nc |
| no_verify | tls | If set to a non-zero value, this disables client checks of the server's certificate. Note that to disable server checks of the client's certificate or IP address you must change the libvirtd configuration. | no_verify=1 |
| no_tty | ssh | If set to a non-zero value, this stops ssh from asking for a password if it cannot log in to the remote machine automatically (for using ssh-agent or similar). Use this when you do not have access to a terminal - for example in graphical programs which use libvirt. | no_tty=1 |
