NAME

       socket-activate - open sockets and exec a systemd-style socket-activated service

SYNOPSIS

       socket-activate [-v] [socketinfo ...]  [--] prog [args]

       where socketinfo is of the form:

       --family:[option=value,...]:address

       See EXAMPLES below.

DESCRIPTION

       The  socket-activate  program  opens  the requested sockets and then waits for incoming activity on them.
       When this happens, it execs prog, which inherits these open file descriptors.  The first requested socket
       will be opened on file descriptor 3, and subsequent ones follow in order.

       If -v or --verbose is present, socket-activate will write details of what it is doing to stderr before it
       execs prog.

       prog is the first argument that does not start with a -, or the first argument after a --.

SOCKET FAMILIES

       family can be one of several different values.

       For the following values of family, if address is a single decimal number, it is treated as a port number
       and socket-activate will bind to all available addresses on that port.  If address contains a /, the part
       before the / is interpreted as a network address of the requested family, and the part  after  the  /  is
       treated as a port number.

       • tcp: TCP on IPv4 and/or IPv6

       • udp: UDP on IPv4 and/or IPv6

       For the following values of family, address is interpreted as a filesystem path.

       • unix: Unix-domain streaming socket

       • unix-dgram: Unix-domain datagram socket

SOCKET OPTIONS

       Each  socketinfo  can  have  0  or more options appended to it, separated by the comma character (,) with
       their value appended after an equals sign (=).

       Available options are:

       • label: simple text string to identify this socket to the inheriting process

       • backlog: For streaming sockets (tcp and unix), the maximum queue for pending connections (see listen(2)
         – defaults to SOMAXCONN).

       • mode: octal mode for Unix-domain socket (defaults to relying on umask(2))

       • user: a numeric User ID value for Unix-domain socket ownership

       • group: a numeric Group ID value for Unix-domain socket ownership

EXIT CODES

       socket-activate exits 100 when called with unparseable options.  It prints an error message to stderr and
       exits 11 if it cannot successfully bind all of the requested sockets.  It  prints  an  error  message  to
       stderr and exits with the value of errno if it is unable to exec(3) the intended process.  Otherwise, its
       exit code is the same as that of prog.

ENVIRONMENT VARIABLES

       socket-activate  stores  the  number  of opened file descriptors in the environment variable $LISTEN_FDS,
       sets $LISTEN_PID to getpid(2), and stores the list of colon-separated labels in $LISTEN_FDNAMES.

       These environment variables follow the convention understood by libsystemd (see sd_listen_fds(3))  so  it
       should be usable with any socket-activated daemon that expects this behavior.

EXAMPLES

       Run  a  webserver as a non-privileged user, using privileged ports, and indicating to the webserver which
       ports should offer HTTPS:

              socket-activate --tcp::80 --tcp:label=tls:443 -- \
               runuser -u httpd -- \
                webserver

       Expose a foregrounded (supervised) pulseaudio daemon to the network:

              socket-activate --tcp:backlog=5:1000 -- \
               pulseaudio --daemonize=no

       Run a network daemon only on the IPv4 loopback:

              socket-activate --tcp::127.0.0.1/9999 -- \
               network-daemon

       Run a network daemon over a unix-domain socket instead of IP:

              socket-activate --unix::/srv/network-access -- \
               network-daemon

       Run a public-facing network daemon with a local socket for the local administrator to control it:

              socket-activate --tcp::443 --unix:label=control,user=1000,mode=0600:/run/xyz/control -- \
               xyzd

SEE ALSO

       exec(3), listen(2), runuser(1), sd_listen_fds(3), umask(2)

AUTHOR

       Mark Hindley <mark@hindley.org.uk>

       Originally written for (socket-activate)[https://gitlab.com/dkg/socket-activate] by Daniel  Kahn  Gillmor
       <dkg@fifthhorseman.net>

July 2024                                                                                     SOCKET-ACTIVATE(1)