systemd-socket-activate - Man Page

• Activate a service when a specific socket is connected: systemd-socket-activate path/to/socket.service
• Activate multiple sockets for a service: systemd-socket-activate path/to/socket1.service path/to/socket2.service
• Pass environment variables to the service being activated: SYSTEMD_SOCKET_ACTIVATION=1 systemd-socket-activate path/to/socket.service
• Activate a service along with a notification socket: systemd-socket-activate path/to/socket.socket path/to/service.service
• Activate a service with a specified port: systemd-socket-activate path/to/socket.service [-l|--listen] 8080

tldr.sh

systemd-socket-activate [Options...] COMMAND [ARGS...]

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 "127​.0​.0​.1:2001"​.

Added in version 230​.

-a,  --accept

Launch an instance of the service program for each connection and pass the connection socket​. May not be combined with --now​.

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​.

--seqpacket

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​.

--inetd

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​.

--fdname=NAME[:NAME​...]

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​.

--now

Start the service program instantly, instead of waiting for a connection on the socket(s)​. May not be combined with --accept​.

Added in version 258​.

-h,  --help

Print a short help text and exit​.

--version

Print a short version string and exit​.

$LISTEN_FDS,  $LISTEN_PID,  $LISTEN_PIDFDID,  $LISTEN_FDNAMES

See sd_listen_fds(3)​.

Added in version 230​.

$SYSTEMD_LOG_TARGET,  $SYSTEMD_LOG_LEVEL,  $SYSTEMD_LOG_TIME,  $SYSTEMD_LOG_COLOR,  $SYSTEMD_LOG_LOCATION

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

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

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