How to see who is logged in and login history in Linux

See who is on the system now and who logged in recently. last reads the wtmp log; lastlog shows the most recent login per account.

# Logged in right now
who
w

# Recent logins and reboots (newest first)
last | head -n 20

# Failed login attempts
sudo lastb | head -n 20

# Most recent login per user
lastlog