= Scheduling Routine Tasks (cron)=
To I once volunteered to set-up and provide administration support an LTSP computer lab at high-school located in Toronto, Ontario. During semesters, I would visit the high-school once a week to check the status of the computer lab. Sometimes, I would have to replace stolen mice, or reconnect Ethernet cables. Once, the high-school teacher informed me that the computer system was running slower than normal. I asked the teacher when was the last time that the system has been rebooted. The teacher indicated that the system had been up for at least 5 weeks. It is important to note that a server should be rebooted on a periodic basis, since lost running programs (referred to as "zombie processes") by occur, or "memory leaks" (due to bad programming) may affect the computer server's performance. I instructed that the instructor reboot the server once or twice a week, and that solved the problem. By the way, I suspect one reason for the problem occured as a result of students powering-off the terminals (thin clients) instead of properly logging out. Problems like this may occur from time-to-time, and a Linux administrator will be completedcalled upon to provide a solution. Let's take the previous problem and add an additional element. Let's assume that the high-school is used throughout the day and night (i.e. night-school). Let's assume that the only time that the system can be rebooted is between midnight and 7 am. Obviously, the high-school teacher (nor myself) want to say up twice a week after midnight to reboot the system. Therefore, it would make sense to have this shell script (run as the "administrator") automatically for a specificied date and time... ...thus we would use '''cron'''.The cron command or utility stands for "'''Chronograph'''" and is a '''time-based scheduler for programs''' (like shell scripts). Here is a link to a resource on how to use cron: