Linux dmesg command

Linux Command Manual

The Linux dmesg command is used to display boot information.

The kernel stores boot information in the ring buffer. If you are not able to view the information at boot time, you can use dmesg to view it. Boot information is also stored in/var/The file named dmesg in the log directory.

Syntax

dmesg [-cn][-s <buffer size>]

Parameter Description:

• -c Clear the content of the ring buffer after displaying the information.
• -s<buffer size> The preset is8196，exactly equal to the size of the ring buffer.
• -n Set the level of information recording.

Online examples

Display Boot Information

# dmesg |less
WARNING: terminal is not fully functional
[  0.000000]  Initializing cgroup subsys cpuset
[  0.000000]  Initializing cgroup subsys cpu
[  0.000000]  Linux version 2.6.32-21-generic (buildd@rothera) (gcc version 4.4.3 (Ub
untu 4.4.3-4ubuntu5) ) #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 (Ubuntu 2.6.32-21.3
2-generic 2.6.32.11+drm33.2)
[  0.000000]  KERNEL supported cpus:
[  0.000000]  Intel GenuineIntel
[  0.000000]  AMD AuthenticAMD
[  0.000000]  NSC Geode by NSC
[  0.000000]  Cyrix CyrixInstead
[  0.000000]  Centaur CentaurHauls
[  0.000000]  Transmeta GenuineTMx86
[  0.000000]  Transmeta TransmetaCPU
[  0.000000]  UMC UMC UMC UMC
[  0.000000] BIOS-Provided Physical RAM Map:
[  0.000000] BIOS-e820: 0000000000000000 - 000000000009f800 (usable)
[  0.000000] BIOS-e820: 000000000009f800 - 00000000000a0000 (reserved)
[  0.000000] BIOS-e820: 00000000000ca000 - 00000000000cc000 (reserved)
[  0.000000] BIOS-e820: 00000000000dc000 - 00000000000e0000 (reserved)
[  0.000000] BIOS-e820: 00000000000e4000 - 0000000000100000 (reserved)
[  0.000000] BIOS-e820: 0000000000100000 - 000000003fef0000 (usable)
[  0.000000] BIOS-e820: 000000003fef0000 - 000000003feff000 (ACPI data)
[  0.000000] BIOS-e820: 000000003feff000 - 000000003ff00000 (ACPI NVS)
……Omitted Content

Display Boot Information

#pwd   //View Current Directory
/home/hnlinux/
# dmesg > boot.msg //Save boot information to boot.msg file
#ls //Display Current Directory Files
boot.msg

Linux Command Manual