Debian Basic Commands

Linux cpu/hardware information

Use any one of the following command:
# less /proc/cpuinfo
OR
# lscpu

Linux show free and used memory in the system

Use any one of the following command:
# cat /proc/meminfo
OR
# free
# free -m
# free -mt
# free -gt

Linux find out the current running kernel version

Type the following command:
# cat /proc/version
Sample outputs:

Linux version 3.2.0-43-generic (buildd@batsu) (gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) ) #68-Ubuntu SMP Wed May 15 03:33:33 UTC 2013

OR use
# uname -mrs
# uname -a

Find out information about the Linux distribution and version

# lsb_release -a
Sample outputs:

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.2 LTS
Release: 12.04
Codename: precise

OR use the following command:
$ cat /etc/*release*
Sample outputs:

Red Hat Enterprise Linux Server release 6.4 (Santiago)

List all PCI devices

# lspci

List all USB devices

# lsusb

List all block devices (hard disks, cdrom, and others)

# lsblk

Dump all hardware information

Type the following command to see your motherboard, cpu, vendor, serial-numbers, RAM, disks, and other information directly from the system BIOS:
# dmidecode | less