dmesg
TLDR
Show kernel messages
$ sudo dmesg
Show kernel error messages$ sudo dmesg -l err
Follow kernel messages in real-time$ sudo dmesg -w
Show messages with human-readable timestamps$ sudo dmesg -T
Show messages in human-readable form$ sudo dmesg -H
Colorize output$ sudo dmesg -L
Filter messages by facility$ sudo dmesg -f kern
SYNOPSIS
dmesg [-l level] [-f facility] [-T] [-H] [-w] [-L]
DESCRIPTION
dmesg prints and controls the kernel ring buffer, which contains messages from the kernel including hardware detection, driver loading, and system events. It is essential for debugging hardware and driver issues.
PARAMETERS
-l, --level level
Restrict output to specified log levels (emerg, alert, crit, err, warn, notice, info, debug)-f, --facility facility
Restrict output to specified facilities (kern, user, mail, daemon, etc.)-T, --ctime
Print human-readable timestamps-H, --human
Enable human-readable output with colors and timestamps-w, --follow
Wait for new messages (like tail -f)-L, --color
Colorize output-c, --read-clear
Clear the ring buffer after printing-C, --clear
Clear the ring buffer without printing-n, --console-level level
Set level of messages printed to console-x, --decode
Decode facility and level to human-readable prefixes
CAVEATS
Requires root privileges on most systems. The -w, -T, and -H options are available in kernels 3.5.0 and newer.
HISTORY
Part of util-linux package. The kernel ring buffer has been part of Linux since early versions, providing essential diagnostic information.
SEE ALSO
journalctl(1), syslog(3), tail(1)
