Troubleshooting services Files

Services files are found in the /etc directory on Unix-like OS, and in the %WINDOWS%\System32\Drivers\etc directories on Windows systems.

All services files use the same simple three-column structure. Anything following a hash (#) character, including an entire line, is treated as a comment. For example:

# servicename     portnumber/porttype     # comment
xns-ch                    54/udp          # XNS Clearinghouse
isi-gl                    55/tcp          # ISI Graphics Language
isi-gl                    55/udp          # ISI Graphics Language
xns-auth                  56/tcp          # XNS Authentication
xns-auth                  56/udp          # XNS Authentication
mtp                       57/tcp          # deprecated
xns-mail                  58/tcp          # XNS Mail

The first column holds the service names. The second column associates a port number and type (tcp or udp) with the service name. The third and final column is an optional human-readable comment which typically details the nature or purpose of the service.

Note that services listed in this file may not actually be running or even installed on the given machine. Many services files include a long list of "well known" and otherwise "standard" port assignments, which may not be relevant in a given deployment.

The services file may be relevant in several scenarios --