To learn more about gathering system information, refer to the following resources.
ps --help — Displays a list of options that can be used with ps.
top manual page — Type man top to learn more about top and its many options.
free manual page — type man free to learn more about free and its many options.
df manual page — Type man df to learn more about the df command and its many options.
du manual page — Type man du to learn more about the du command and its many options.
lspci manual page — Type man lspci to learn more about the lspci command and its many options.
/proc — The contents of the /proc directory can also be used to gather more detailed system information. Refer to the Red Hat Linux Reference Guide for additional information about the /proc directory.