Linux System Information

uname -a # all system information
uname -r # kernel version
hostname # system hostname
uptime # system uptime

lscpu # CPU information
lsblk # block devices (disks)
lsusb # USB devices
lspci # PCI devices

free -h # memory usage
df -h # disk space usage
du -h directory # directory size
du -sh * # size of each item

cat /etc/os-release # OS details
lsb_release -a # distribution info

whoami # current user
who # logged in users
w # users and what they are doing
last # login history

date # current date and time
cal # calendar
timedatectl # time and date settings