System Information

dmesg Linux Command

Prints the kernel ring buffer messages (boot-time and hardware diagnostics).

What does dmesg do?

Prints the kernel ring buffer messages (boot-time and hardware diagnostics).

dmesg [options]

dmesg | tail -20

How do I see kernel messages?

Use `dmesg` to display kernel ring buffer messages. This includes boot messages, hardware detection, and driver errors.

How do I see the last 20 kernel messages?

Use `dmesg | tail -20` to see only the most recent kernel messages without scrolling through all output.

How do I watch kernel messages in real time?

Use `dmesg -w` or `tail -f /var/log/dmesg` to watch kernel messages as they are generated.

How do I see hardware errors with dmesg?

Use `dmesg | grep -i error` to filter kernel messages for error conditions, especially hardware-related issues.

How do I clear the kernel ring buffer?

Use `sudo dmesg -c` to clear the ring buffer. This is useful after reviewing messages you no longer need.

How do I see USB device messages?

Use `dmesg | grep -i usb` to see messages related to USB device connections and disconnections.

How do I see disk errors?

Use `dmesg | grep -i 'error|fail|disk'` to find disk-related errors and failures in kernel messages.

How do I see timestamped kernel messages?

Use `dmesg -T` to show human-readable timestamps instead of seconds since boot.

Reports virtual memory statistics including CPU, memory, and I/O.

Lists all currently loaded kernel modules.

Displays the amount of free and used system memory (RAM and swap).

Displays detailed information about a specific kernel module.

Lists all USB devices connected to the system.

Displays all current environment variables.