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systemd-socket-activate - Man Page

Test socket activation of daemons

Examples (TL;DR)


systemd-socket-activate [Options...] daemon [Options...]


systemd-socket-activate may be used to launch a socket-activated service program from the command line for testing purposes. It may also be used to launch individual instances of the service program per connection.

The daemon to launch and its options should be specified after options intended for systemd-socket-activate.

If the --inetd option is given, the socket file descriptor will be used as the standard input and output of the launched process. Otherwise, standard input and output will be inherited, and sockets will be passed through file descriptors 3 and higher. Sockets passed through $LISTEN_FDS to systemd-socket-activate will be passed through to the daemon, in the original positions. Other sockets specified with --listen= will use consecutive descriptors. By default, systemd-socket-activate listens on a stream socket, use --datagram and --seqpacket to listen on datagram or sequential packet sockets instead (see below).


-l address, --listen=address

Listen on this address. Takes a string like "2000" or "".

Added in version 230.

-a,  --accept

Launch an instance of the service program for each connection and pass the connection socket.

Added in version 230.

-d,  --datagram

Listen on a datagram socket (SOCK_DGRAM), instead of a stream socket (SOCK_STREAM). May not be combined with --seqpacket.

Added in version 230.


Listen on a sequential packet socket (SOCK_SEQPACKET), instead of a stream socket (SOCK_STREAM). May not be combined with --datagram.

Added in version 230.


Use the inetd protocol for passing file descriptors, i.e. as standard input and standard output, instead of the new-style protocol for passing file descriptors using $LISTEN_FDS (see above).

Added in version 230.

-E VAR[=VALUE], --setenv=VAR[=VALUE]

Add this variable to the environment of the launched process. If VAR is followed by "=", assume that it is a variable–value pair. Otherwise, obtain the value from the environment of systemd-socket-activate itself.

Added in version 230.


Specify names for the file descriptors passed. This is equivalent to setting FileDescriptorName= in socket unit files, and enables use of sd_listen_fds_with_names(3). Multiple entries may be specifies using separate options or by separating names with colons (":") in one option. In case more names are given than descriptors, superfluous ones will be ignored. In case less names are given than descriptors, the remaining file descriptors will be unnamed.

Added in version 230.

-h,  --help

Print a short help text and exit.


Print a short version string and exit.

Environment Variables


See sd_listen_fds(3).

Added in version 230.


Same as in systemd(1).

Added in version 230.


Example 1. Run an echo server on port 2000

$ systemd-socket-activate -l 2000 --inetd -a cat

Example 2. Run a socket-activated instance of systemd-journal-gatewayd(8)

$ systemd-socket-activate -l 19531 /usr/lib/systemd/systemd-journal-gatewayd

See Also

systemd(1), systemd.socket(5), systemd.service(5), systemd-run(1), sd_listen_fds(3), sd_listen_fds_with_names(3), cat(1)

Referenced By

systemd.directives(7), systemd.index(7).

systemd 256.2