mirror of
https://gitlab.com/libvirt/libvirt.git
synced 2024-12-22 13:45:38 +00:00
86 lines
2.7 KiB
ReStructuredText
86 lines
2.7 KiB
ReStructuredText
|
=================
|
||
|
|
Libvirt SSH proxy
|
||
|
|
=================
|
||
|
|
|
||
|
|
Sometimes it's necessary to run some commands inside a guest. While libvirt
|
||
|
|
already provides a `NSS module <nss.html>`__ that can translate guest name to
|
||
|
|
IP address it has some limitations (e.g. guest has to have a network interface
|
||
|
|
plugged into a libvirt-managed network). To resolve some of these limitations,
|
||
|
|
libvirt offers a SSH proxy. It consists of a SSH client config file
|
||
|
|
(``/etc/ssh/ssh_config.d/30-libvirt-ssh-proxy.conf``) and a small binary. Both
|
||
|
|
are automatically installed by ``libvirt-ssh-proxy`` package which is dragged
|
||
|
|
in by ``libvirt-client``, ``libvirt-daemon-qemu`` and/or ``daemon-kvm`` RPM
|
||
|
|
packages. After running either of:
|
||
|
|
|
||
|
|
::
|
||
|
|
|
||
|
|
ssh user@qemu:system/virtualMachine
|
||
|
|
ssh user@qemu:session/virtualMachine
|
||
|
|
|
||
|
|
the configuration file instructs SSH client to start the binary helper which
|
||
|
|
finds a VSOCK device inside the ``virtualMachine`` and establishes a connection
|
||
|
|
to it.
|
||
|
|
|
||
|
|
For now, only QEMU domains are implemented and the lookup of the
|
||
|
|
``virtualMachine`` is done under ``qemu:///system`` URI for ``qemu:system`` or
|
||
|
|
under ``qemu:///session`` URI for ``qemu:session``.
|
||
|
|
|
||
|
|
For convenience, there's also another alternative:
|
||
|
|
|
||
|
|
::
|
||
|
|
|
||
|
|
ssh user@qemu/virtualMachine
|
||
|
|
|
||
|
|
where the ``virtualMachine`` is looked up under ``qemu:///system`` first,
|
||
|
|
possibly followed by ``qemu:///session`` (for cases where ssh client runs as
|
||
|
|
non-root, since there's no ``qemu:///session`` for root).
|
||
|
|
|
||
|
|
Accepted values for ``virtualMachine`` are: domain name (as reported by e.g.
|
||
|
|
`virsh list`), domain UUID and finally domain ID.
|
||
|
|
|
||
|
|
Guest OS requirements
|
||
|
|
---------------------
|
||
|
|
|
||
|
|
It is obvious that the SSH daemon inside the guest needs to be configured to
|
||
|
|
listen for incoming connections on a VSOCK. There are couple of ways to achieve
|
||
|
|
this:
|
||
|
|
|
||
|
|
* Run systemd-v256 or newer inside the guest.
|
||
|
|
|
||
|
|
In this release, systemd started to deploy ``systemd-ssh-generator`` which
|
||
|
|
should configure socket activation for SSHD automagically.
|
||
|
|
|
||
|
|
* Set up socket activation for VSOCK.
|
||
|
|
|
||
|
|
We can take an inspiration in the unit file generated by
|
||
|
|
``systemd-ssh-generator``:
|
||
|
|
|
||
|
|
::
|
||
|
|
|
||
|
|
[Unit]
|
||
|
|
Description=OpenSSH Server Socket (systemd-ssh-generator, AF_VSOCK)
|
||
|
|
Documentation=man:systemd-ssh-generator(8)
|
||
|
|
Wants=ssh-access.target
|
||
|
|
Before=ssh-access.target
|
||
|
|
|
||
|
|
[Socket]
|
||
|
|
ListenStream=vsock::22
|
||
|
|
Accept=yes
|
||
|
|
PollLimitIntervalSec=30s
|
||
|
|
PollLimitBurst=50
|
||
|
|
|
||
|
|
* Run a service that forwards VSOCK <=> SSHD communication
|
||
|
|
|
||
|
|
For instance:
|
||
|
|
|
||
|
|
::
|
||
|
|
|
||
|
|
socat VSOCK-LISTEN:22,reuseaddr,fork TCP:localhost:22
|
||
|
|
|
||
|
|
Libvirt domain XML configuration
|
||
|
|
--------------------------------
|
||
|
|
|
||
|
|
Since the SSH proxy uses a VSOCK to communicate with the SSH daemon running
|
||
|
|
inside the guest, it is a must to configure VSOCK in the `domain XML
|
||
|
|
<formatdomain.html#vsock>`__.
|