SIGHUP

For this reason, applications that did not require a controlling terminal, such as daemons, would re-purpose SIGHUP as a signal to re-read configuration files, or reinitialize.

Firstly, the Single UNIX Specification describes a shell utility called nohup, which can be used as a wrapper to start a program and make it ignore SIGHUP by default.

Different shells also have other methods of controlling and managing SIGHUP, such as the disown facility of ksh.

Most modern Linux distributions documentation specify using kill -HUP to send the SIGHUP signal.

[3] Daemon programs sometimes use SIGHUP as a signal to restart themselves, the most common reason for this being to re-read a configuration file that has been changed.

A hangup was often the result of a connected user physically hanging up the modem