sending a HUP to a program (kill)From time to time, you need to tell a program to HUP (Hang UP). This causes the program to restart and examine its configuration files. This is especially useful if you have changed the configuration settings. There are two commands you can use for this: kill and killall.
killkill kills a process by its process id.
After a configuration file is modified, you can send a signal to the program to inform it that changes have been made and that it should reread the file. This is done using the kill command. The first thing you need is the process id of the program.
This example shows how to restart inetd after a change has been made to /etc/inetd.conf.
[root@ns:~] # ps -auwx | grep inetd root 1368 2.3 1.0 176 132 p1 R+ 12:51PM 0:00.14 grep inetd root 128 0.0 0.0 212 0 ?? IWs - 0:00.00 (inetd) [root@ns:~] # kill -HUP 128
In this example, the process id for inetd is 128. The other process is the grep command.
For more information about the kill command, see man kill.
killallkillall kills a process by its name. In the above example, we could achieve the same thing by doing:
[root@ns:~] # killall -HUP inetd
killall is much easier than then kill in that it does not require a process ID.
Notes of warningYou shouldn’t use kill or killall on Apache. See Apache – starting/stopping for more information.
Also, for named, you should use ndc to send a HUP etc. For example, after changing your zone files, you should do the following to reload named: