dmesg

shows kernel ring buffer (kernel logs in memory)

[    0.000000] Linux version 6.x
[    1.234567] usb 1-1: new device
[    5.678901] eth0: link up

• Boot events
• Hardware/devices (USB, disks)
• Driver activity
• Network interface changes

# detect USB insertions
dmesg | grep -i usb 

# latest events
dmesg | tail