Learning Red Hat Linux, Third 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 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. With the -s option, displays just a summary without listing all the subdirectories and files.
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, ...