Learning Red Hat Linux, Second Edition

Useful Linux Programs

This section presents several programs you may find helpful in working with your Linux system. You’ll learn several commands that report system status, and you’ll also learn how to use pico, a simple text editor.

Viewing System Information

Linux provides a number of commands that report system status. The most commonly used commands are shown in Table 7-8. These commands can help you troubleshoot system problems and identify resource bottlenecks. Although each command can be used without options or arguments, each supports options and arguments that let you customize operation and output; consult the appropriate manpage for details.

Table 7-8. Useful System Commands

Command	Function
df	Shows the amount of free disk space (in 1 KB blocks) on each mounted filesystem
du	Shows the amount of disk space (in 1 KB blocks) used by the working directory and its subdirectories
free	Shows memory usage statistics, including total free memory, memory used, physical memory, swap memory, shared memory, and buffers used by the kernel
ps	Shows the active processes (instances of running programs) associated with this login session; use the -a option to list all processes
top	Shows a continually updated display of active processes and the resources they are using; type the Q key to exit
uptime	Shows the current time, the amount of time logged in, the number of users logged in, and system load averages
users	Shows each login session
w