Banish your daemons for a faster Linux PC

Cron, Anacron and atd
Likelihood that you'll miss it: 3/5
If you've ever used Cron to schedule the execution of a particular task at a specific time, you'll know exactly what the Cron daemon is responsible for. It patiently waits in the background for the correct date and time, before dutifully executing the command held in its configuration files. You can check exactly what Cron is getting up to by looking at the contents of /etc/crontab, and if you're happy to exclude those tasks from your system, you can safely disable Cron. A close cousin to Cron is called Anacron. This can be found running on Ubuntu, but not on OpenSUSE 11. The difference between Cron and Anacron is that Anacron ensures tasks are run even when the system isn't running. It will make sure a backup scheduled for the night before will be run when the machine is turned on. For this reason, Anacron is more likely to be used for system tasks. In a similar vein, you'll find the atd daemon, which controls the scheduling of tasks executed with the at command. This would normally be a non-recurring command that needs to be run at a specific time.

AppArmor
Likelihood that you'll miss it: 3/5
Both OpenSUSE and Ubuntu use AppArmor to beef up security. It stops one compromised tool being able to wreak havoc on the rest of the system. That's definitely a good thing. But if you can be sure that your system is not going to be compromised or at risk because it's not on a network, running AppArmor makes very little sense and you should disable the daemon. Otherwise, we'd recommend you keep it running.

Apport
Likelihood that you'll miss it: 2/5
This is the background crash-reporting service in Ubuntu. You've probably seen it in action when an application crashes, as it's apport that's responsible for the window that appears explaining what's happened, and asks whether you'd like to report the fault to the Ubuntu team. It's a very useful tool for the Ubuntu developers, because it enabled them to get reports from a massive install base where their distribution is being used in all kinds of environments. Apport doesn't have an immediate effect on the user, but if everyone disables it, the rate at which developers add bugfixes and stability improvements may slow down.

Avahi-daemon
Likelihood that you'll miss it: 1/5
Avahi provides automatic discovery of various network services. In theory, it should be a great help for laptop users, as Avahi should simplify the detection of services like printing or file sharing – except that this rarely seems to happen. And it's going to be even less useful for desktop users, as they're even less likely to change their network regularly enough to reap the benefits.

Bluetooth
Likelihood that you'll miss it: 1/5
If your computer isn't equipped with a Bluetooth device, then you don't need to run the bluetooth daemon. Its only job is to wait for remote Bluetooth devices to connect, and pass on those connections to any Bluetooth management utilities that might be running, such as those provided by both Gnome and KDE. While Bluetooth hardware is commonly found on portable devices and laptops, there are relatively few desktop machines with this ability. For this reason, deciding whether to leave this daemon running or disabling it should be easy.

CUPS
Likelihood that you'll miss it: 2/5
CUPS is the printing daemon. It's responsible for picking up print jobs from the various applications you use and sending them to your printer. This obviously means that if you don't have a printer, you don't need to run CUPS.

GPM
Likelihood that you'll miss it: 1/5
All this daemon does is add mouse support for the pure console view. If you run a desktop, you're hardly ever going to need this facility. The only times you might need it is when you need to run your system at a lower runlevel, in which case it might make sense to enable it for runlevels 1 and 2, and not for 3 and 4.

KLogd
Likelihood that you'll miss it: 3/5
KLog is the process that creates your system logs. These are an essential part of any system, especially if your machine acts as some kind of server. But then you have to ask yourself when the last time you took a looked at those log files was. If the answer is 'never', you won't lose anything by disabling this daemon.

NTP
Likelihood that you'll miss it: 4/5
The Network Time Protocol will sync your local clock with the date and time on a couple of remote machines. It's a great way to keep your local time exactly right, and NTP will automatically update your machine for daylight savings time.