Linux Command for System Information

uname -r
To display the info more about kernel.

free
Memory info (in kilobytes).

df -h
(disk free) Print disk info about all the filesystems in human-readable form.

du / -bh | more
(=disk usage) Print detailed disk usage for each subdirectory starting at the "/" (root) directory (in human legible form).

cat /proc/cpuinfo
Cpu info--it show the content of the file cpuinfo.

cat /proc/interrupts
List the interrupts in use.

cat /proc/version
Linux version and other info

cat /proc/filesystems
Show the types of filesystems currently in use.

cat /etc/printcap
Show the setup of printers.

lsmod
Show the kernel modules currently loaded.(As root. Use /sbin/lsmod to execute this command when you are a non-root user.)

set|more
Show the current user environment.

echo $PATH
Show the content of the environment variable "PATH". This command can be used to show other environment variables as well. Use "set" to see the full environment.

dmesg | less
Print kernel messages (the content of the so-called kernel ring buffer). Use less /var/log/dmesg  to see what "dmesg" dumped into this file right after the last system bootup.