选题: Understanding /etc/services file in Linux

sources/tech/20190109 Understanding -etc-services file in Linux.md

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+[#]: collector: (lujun9972)
+[#]: translator: ( )
+[#]: reviewer: ( )
+[#]: publisher: ( )
+[#]: url: ( )
+[#]: subject: (Understanding /etc/services file in Linux)
+[#]: via: (https://kerneltalks.com/linux/understanding-etc-services-file-in-linux/)
+[#]: author: (kerneltalks https://kerneltalks.com)
+
+Understanding /etc/services file in Linux
+======
+
+Article which helps you to understand /etc/services file in Linux. Learn about content, format & importance of this file.
+
+![/etc/services file in Linux][1]
+/etc/services file in Linux
+
+Internet daemon is important service in Linux world. It takes care of all network services with the help of `/etc/services` file. In this article we will walk you through content, format of this file and what it means to a Linux system.
+
+`/etc/services` file contains list of network services and ports mapped to them. `inetd` or `xinetd` looks at these details so that it can call particular program when packet hits respective port and demand for service.
+
+As a normal user you can view this file since file is world readable. To edit this file you need to have root privileges.
+
+```
+$ ll /etc/services
+-rw-r--r--. 1 root root 670293 Jun  7  2013 /etc/services
+```
+
+### `/etc/services` file format
+
+```
+service-name    port/protocol   [aliases..]  [#comment]
+```
+
+Last two fields are optional hence denoted in `[` `]`
+
+where –
+
+  * service-name is name of the network service. e.g. [telnet][2], [ftp][3] etc.
+  * port/protocol is port being used by that network service (numerical value) and protocol (TCP/UDP) used for communication by service.
+  * alias is alternate name for service.
+  * comment is note or description you can add to service. Starts with `#` mark
+
+
+
+### Sample` /etc/services` file
+
+```
+# Each line describes one service, and is of the form:
+#
+# service-name  port/protocol  [aliases ...]   [# comment]
+
+tcpmux          1/tcp                           # TCP port service multiplexer
+rje             5/tcp                           # Remote Job Entry
+echo            7/udp
+discard         9/udp           sink null
+```
+
+Here, you can see use of optional last two fields as well. `discard` service has alternate name as `sink` or `null`.
+
+--------------------------------------------------------------------------------
+
+via: https://kerneltalks.com/linux/understanding-etc-services-file-in-linux/
+
+作者：[kerneltalks][a]
+选题：[lujun9972][b]
+译者：[译者ID](https://github.com/译者ID)
+校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
+
+[a]: https://kerneltalks.com
+[b]: https://github.com/lujun9972
+[1]: https://i2.wp.com/kerneltalks.com/wp-content/uploads/2019/01/undestanding-etc-service-file-in-linux.png?ssl=1
+[2]: https://kerneltalks.com/config/configure-telnet-server-linux/
+[3]: https://kerneltalks.com/config/ftp-server-configuration-steps-rhel-6/