Linux system information

Linux distro

dmesg | head -1 
cat /proc/version 
cat /etc/issue 
uname -a 
lsb_release -a 
arch 
uname -m 

System information

lshw 
lscpu 
lshal 
lspci 
lsusb 
Dmidecode

Kernel version and system architecture

uname -a

Name and version of the distro

head -n1 /etc/issue

Partition information

cat /proc/partitions

Memory information

grep MemTotal /proc/meminfo 
free -m

CPU information

grep "model name" /proc/cpuinfo

HDD information

hdparm -i /dev/sda 
fdisk -l /dev/sda