If you use your Red Hat Linux system for production work (to run an Internet server or an office server, for example), you have to perform some advanced systems-administration tasks. This chapter introduces you to some systems-administration tasks I do not cover elsewhere in the book.
By reading this chapter, you learned the following:
After Linux boots, a process named init starts all other processes. The exact set of initial processes depends on the run level, which typically is a number ranging from 0 to 6. The /etc/inittab file specifies the processes that start in each run level.
The /etc/inittab file specifies that a graphical display manager starts at run level 5. In Red Hat Linux, the display manager provides the graphical login prompt.
The init process executes Red Hat Linux startup scripts in the /etc/rc.d directory and its subdirectories.
You can use the /sbin/chkconfig program to set up servers to start automatically at various run levels.
You can use the at command to execute one or more commands at a future time and have the output mailed to you.
You can use the crontab facility to set up periodic jobs (called cron jobs) that are executed at recurring intervals. Then, you can have the output mailed to you.
If you use your Red Hat Linux system for anything important, you have to back up your files. You should select a backup strategy and backup media based on your needs and your level of tolerance for the risk of business interruption from a hard disk failure.
You can use the tape archiver program-tar-to back up and restore files. This chapter shows you how to set up cron jobs for automated full and incremental backups.
Red Hat Linux comes with utilities and commands you can use to keep an eye on your system's performance. You learn to use and interpret the displays produced by top, the GNOME System Monitor, and vmstat. Also, you learn some commands to check available disk space and your hard disk's performance.
The /proc file system contains extensive information about the system. The /proc file system is not a disk-based file system; it is a collection of data structures in memory, managed by the Linux kernel, that appears to the user as a set of directories and files.
In the /proc/sys directory are a number of files whose values you can set to modify the kernel's behavior at run time. You can either directly write to these files or use the /sbin/sysctl program to view or set the parameters. If you know what you are doing, you can tune the performance of your system by modifying the parameters in the /proc/sys directory.