hw general

sudo lshw # lists all recognized hardwarecomponents
sudo lshw -html > -pc.html # output as html in file

pci

lspci # lists all devices - if not even the vendor is known the hardware might be too new for the kernel

memory

cat /proc/meminfo

cpu

cat /proc/cpuinfo

hard drive

free/used space
df -h
partioning
sudo fdisk -l # lists all harddisk patition tables -doesnt work with Xubuntu
sudo cfdisk /dev/XdX # semi graphical harddisk partitioning tool
gksudo qtparted # graphical partitioning tool (kde)
gksudo gparted # graphical partitioning tool (gnome/xfce)

sound

list all soundcards and digital audio devices recognized by your system
aplay -l
Codec information
cat /proc/asound/card0/codec#0 

distribution & release

lsb_release -a #  (ubuntu only)
cat /etc/apt/sources.list # on apt based systems (like ubuntu, xubuntu, debian,..) contains distribution version (repository) information 

kernel

Linux Kernel version:
uname -a

 

links

1 Hardware Identification

2 Using the Terminal

3 Malicious Commands