/etc/services

Internal

• Linux

Overview

/etc/services is called the "services file" and it stores the mapping between a conventional name and standard IANA port numbers allocated to services and the associated protocol (UDP or TCP). It can optionally store aliases and comments.

The idea behind storing the name - port number mapping in a file is that programs (services) can do a getportbyname() socket call and get the port number they should use. For example, PostgreSQL does a getportbyname ("postgres") and gets 5432/tcp. If the service always uses getportbyname(), then no matter what service is run, the port number can be always reconfigured by editing /etc/services.

Syntax

name port/protocol aliases comments

Example

# /etc/services:
# $Id: services,v 1.55 2013/04/14 ovasik Exp $
#
# Network services, Internet style
# IANA services version: last updated 2013-04-10
#
# Note that it is presently the policy of IANA to assign a single well-known
# port number for both TCP and UDP; hence, most entries here have two entries
# even if the protocol doesn't support UDP operations.
# Updated from RFC 1700, ``Assigned Numbers'' (October 1994).  Not all ports
# are included, only the more common ones.
#
# The latest IANA port assignments can be gotten from
#       http://www.iana.org/assignments/port-numbers
# The Well Known Ports are those from 0 through 1023.
# The Registered Ports are those from 1024 through 49151
# The Dynamic and/or Private Ports are those from 49152 through 65535
#
# Each line describes one service, and is of the form:
#
# service-name  port/protocol  [aliases ...]   [# comment]

tcpmux          1/tcp                           # TCP port service multiplexer
tcpmux          1/udp                           # TCP port service multiplexe
[...]
iqobject        48619/tcp               # iqobject
iqobject        48619/udp               # iqobject
matahari        49000/tcp               # Matahari Broker