Nice and Renice
Many UNIX users are very familiar with nice and renice, and as they pertain to job control they deserve mention within this context. The nice command is used to alter an initial job priority. On Linux systems this is fairly simple: the lower the nice command the higher the priority. The range on a Linux system is -20 (being the highest) to 19 (the lowest). Using nice is pretty simple. Let's say we want to make sure that a compile and install for fetchmail has a pretty high priority. We might do the following:

nice -n 5 make

We have lowered the nice number and raised the job priority initially for this task.

The renice command is used to alter the nice value of a job after it has been started. It is important to note that only root may alter the nice value of jobs it does not own, and non-root users may only alter their nice values between 0 and 20 (the former is obviously so users may not tamper with other users while the latter protects the privileged processes of the system). An example of using renice on a single process might look like so:

renice 5 -p 10023

where we lower the nice value to 5 of PID 10023. The renice command can also affect entire group of processes as well. For instance, let us say we wanted all of jdoe user's processes to have a nice value of 12. The syntax on Linux would be:

renice 12 -u jdoe