systemd-ssh-proxy(1) — Linux manual page

NAME \| SYNOPSIS \| DESCRIPTION \| EXIT STATUS \| EXAMPLES \| SEE ALSO \| NOTES \| COLOPHON

SYSTEMD-SSH-PROXY(1)        systemd-ssh-proxy        SYSTEMD-SSH-PROXY(1)

NAME top

       systemd-ssh-proxy - SSH client plugin for connecting to AF_VSOCK
       and AF_UNIX sockets

SYNOPSIS top

       Host unix/* unix%* vsock/* vsock%* vsock-mux/* vsock-mux%*
           ProxyCommand /usr/lib/systemd/systemd-ssh-proxy %h %p
           ProxyUseFdpass yes

       /usr/lib/systemd/systemd-ssh-proxy [ADDRESS] [PORT]

DESCRIPTION top

systemd-ssh-proxy is a small "proxy" plugin for the ssh(1) tool
that allows connecting to AF_UNIX and AF_VSOCK sockets. It
implements the interface defined by ssh's ProxyCommand
configuration option. It's supposed to be used with an
ssh_config(5) configuration fragment like the following:

Host unix/* unix%* vsock/* vsock%* vsock-mux/* vsock-mux%*
ProxyCommand /usr/lib/systemd/systemd-ssh-proxy %h %p
ProxyUseFdpass yes
CheckHostIP no

Host .host
ProxyCommand /usr/lib/systemd/systemd-ssh-proxy unix/run/ssh-unix-local/socket %p
ProxyUseFdpass yes
CheckHostIP no

A configuration fragment along these lines is by default installed
into /etc/ssh/ssh_config.d/20-systemd-ssh-proxy.conf.

With this in place, SSH connections to host string "unix/"
followed by an absolute AF_UNIX file system path to a socket will
be directed to the specified socket, which must be of type
SOCK_STREAM. Similar, SSH connections to "vsock/" followed by an
AF_VSOCK CID will result in an SSH connection made to that CID.
"vsock-mux/" followed by an absolute AF_UNIX file system path to a
socket is similar but for cloud-hypervisor/firecracker which do
not allow direct AF_VSOCK communication between the host and
guests, and provide their own multiplexer over AF_UNIX sockets.
See cloud-hypervisor VSOCK support[1] and Using the Firecracker
Virtio-vsock Device[2]. Note that "%" can be used as a separator
instead of "/" to be compatible with tools like "scp" and "rsync".

Moreover, connecting to ".host" will connect to the local host via
SSH, without involving networking.

This tool is supposed to be used together with
systemd-ssh-generator(8) which when run inside a VM or container
will bind SSH to suitable addresses. systemd-ssh-generator is
supposed to run in the container or VM guest, and
systemd-ssh-proxy is run on the host, in order to connect to the
container or VM guest.

EXIT STATUS top

       On success, 0 is returned, a non-zero failure code otherwise.

EXAMPLES top

       Example 1. Talk to a local VM with CID 4711

           ssh vsock/4711

       Example 2. Talk to a VM guest hosted with
       cloud-hypervisor/firecracker

           ssh vsock-mux/run/vm-1234.sock

       Example 3. Talk to the local host via ssh

           ssh .host

       or equivalent:

           ssh unix/run/ssh-unix-local/socket

       Example 4. Copy local 'foo' file to a local VM with CID 1348

           scp foo vsock%1348:

NOTES top

        1. cloud-hypervisor VSOCK support
           https://github.com/cloud-hypervisor/cloud-hypervisor/blob/main/docs/vsock.md

        2. Using the Firecracker Virtio-vsock Device
           https://github.com/firecracker-microvm/firecracker/blob/main/docs/vsock.md

COLOPHON top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a
       bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2025-08-11.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there is
       a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       [email protected]

systemd 258~rc2                                      SYSTEMD-SSH-PROXY(1)

Pages that refer to this page: systemd.directives(7), systemd.index(7), systemd-ssh-generator(8)