inetdThe file /etc/inetd.conf tells inetd which ports to listen to
and what server programs to run for them. Normally each entry in the
file is one line, but you can split it onto multiple lines provided
all but the first line of the entry start with whitespace. Lines that
start with ‘#’ are comments.
Here are two standard entries in /etc/inetd.conf:
ftp stream tcp nowait root /libexec/ftpd ftpd
talk dgram udp wait root /libexec/talkd talkd
An entry has this format:
service style protocol wait username program arguments
The service field says which service this program provides. It
should be the name of a service defined in /etc/services.
inetd uses service to decide which port to listen on for
this entry.
The fields style and protocol specify the communication style and the protocol to use for the listening socket. The style should be the name of a communication style, converted to lower case and with ‘SOCK_’ deleted—for example, ‘stream’ or ‘dgram’. protocol should be one of the protocols listed in /etc/protocols. The typical protocol names are ‘tcp’ for byte stream connections and ‘udp’ for unreliable datagrams.
The wait field should be either ‘wait’ or ‘nowait’.
Use ‘wait’ if style is a connectionless style and the
server, once started, handles multiple requests as they come in.
Use ‘nowait’ if inetd should start a new process for each message
or request that comes in. If style uses connections, then
wait must be ‘nowait’.
user is the user name that the server should run as. inetd runs
as root, so it can set the user ID of its children arbitrarily. It's
best to avoid using ‘root’ for user if you can; but some
servers, such as Telnet and FTP, read a username and password
themselves. These servers need to be root initially so they can log
in as commanded by the data coming over the network.
program together with arguments specifies the command to run to start the server. program should be an absolute file name specifying the executable file to run. arguments consists of any number of whitespace-separated words, which become the command-line arguments of program. The first word in arguments is argument zero, which should by convention be the program name itself (sans directories).
If you edit /etc/inetd.conf, you can tell inetd to reread the
file and obey its new contents by sending the inetd process the
SIGHUP signal. You'll have to use ps to determine the
process ID of the inetd process as it is not fixed.