nohup

I was reading the FreeBSD Questions mailing list (an always fascinating source of information), when I came across this response by David G. to someone who was having a problem with their KDE taskbar and desktop disappearing:

if you can get a command line up, can you do "nohup kicker &"?


(I have to restart kicker every month or two)

I found it interesting because I had never heard of either nohup or kicker! So, being the curious sort, I decided to look into both.

nohup

First up was this nohup command. First stop is, of course, the man page for nohup. But it is its usual terse self, telling me something about "at this time sets the signal SIGHUP to be ignored.". Well, I'm a programmer, and I'm still not sure what this means! A little more Googling leads me to this definition:

nohup : Runs a command that keeps running after you log out

Ah, now I get it. Normally, when you run a program in the background (by appending the & to the command), it automagically stops running when you completely logout. This isn't always true, as a program can disconnect completely from your session and continue running (this is what a daemon does). But if you have a program that isn't normally a daemon, or something you want to leave running after you've logged out (say, if you log in as root to get a server to run), you can use the nohup command. So David is saying that he is re-running this kicker command as a daemon process, and using nohup means it will stay running after he logs out.

kicker

A quick search on the KDE home page lead me to this page: The Kicker Handbook. It is headlined with this grammatically challenged note:

Kicker is the KDE application starter panel and is also capable of some useful applets and extensions. It usually resides on the bottom of the desktop.

Ah, so it is the task bar that runs along to bottom of the monitor. So the nohup kicker & command restarts the kicker process for others to use. See, you just never know when there is an interesting comment on the FreeBSD Questions mailing list!