BSD Today: inetd and inetd.conf – Managing Your System’s Internet Switchboard Operator

[ Thanks to Jeremy
Reed for this link. ]

“The file /etc/inetd.conf is vitally important to your
system’s security and well-being — especially if your system has a
24×7 connection to the Internet. Many common security holes in
UNIX systems (and UNIX-like systems such as Linux) are the result
of entries in inetd.conf that should have been “commented out” or
removed. On the other hand, an omitted entry can cause your system
to consume extra memory or swap space, or make it more susceptible
to denial of service attacks.”

“As the name implies, /etc/inetd.conf is the configuration file
for inetd, the “Internet daemon.” In the early days of UNIX, when a
10 MB hard drive was considered to be huge and system memory was
measured in kilobytes instead of megabytes, inetd was devised as a
way to save valuable RAM and disk swap space.”

“Prior to inetd, each “daemon” — that is, a program which
provided an Internet service — had to be in memory, waiting for
requests, at all times. But there was a problem: keeping that code
loaded and ready to run consumed valuable system resources. As the
repertoire of services provided by systems on the Internet (then
the ARPANet) grew, systems were in peril of being overrun by
daemons, leaving no space for programs that did other work.”

“Enter inetd. Acting as a sort of switchboard operator, inetd
fields incoming requests for other daemons. When a “call” comes in,
inetd starts up a copy of the appropriate daemon and “transfers the
call” to it. Thus, no Internet daemon — other than inetd itself,
of course — must remain in memory when it’s not providing a
service.”

Complete
Story