功能说明：显示开机信息。

语　　法：dmesg [-cn][-s <缓冲区大小>]

补充说明：kernel会将开机信息存储在ring buffer中。您若是开机时来不及查看信息，可利用dmesg来查看。开机信息亦保存在/var/log目录中，名称为dmesg的文件里。

参　　数：

　-c 　显示信息后，清除ring buffer中的内容。 

　-s<缓冲区大小> 　预设置为8196，刚好等于ring buffer的大小。 

　-n 　设置记录信息的层级。

扩展阅读一:dmesg命令主要用途

主要应用：

dmesg用来显示内核环缓冲区（kernel-ring buffer）内容，内核将各种消息存放在这里。在系统引导时，内核将与硬件和模块初始化相关的信息填到这个缓冲区中。内核环缓冲区中的消息对于诊断系统问题 通常非常有用。在运行dmesg时，它显示大量信息。通常通过less或grep使用管道查看dmesg的输出，这样可以更容易找到待查信息。例如，如果发现硬盘性能低下，可以使用dmesg来检查它们是否运行在DMA模式：

$dmesg | grep DMA

...
ide0: BM-DMA at 0xf000-0xf007, BIOS settings:
hda:DMA, hdb:DMA

ide1: BM-DMA at 0xf008-0xf00f, BIOS settings: hdc:DMA, hdd:DMA

...

上面几行可以说明每个IDE设备正在什么模式下运行。如果以太网连接出现问题，那么可以在dmesg日志中搜索eth：

$dmesg | grep eth

forcedeth.c: Reverse Engineered nForce

ethernet driver. Version 0.49.

eth0: forcedeth.c: subsystem: 0147b:1c00

bound to 0000:00:04.0

eth0: no IPv6 routers present

如果一切正常，那么dmesg显示每个网卡的硬件配置信息。如果某项系统服务未能得到正确的配置，dmesg日志很快就填满错误消息，这是诊断故障的良好起点。

还可以用来探测系统内核模块的加载情况，比如要检测ACPI的加载情况，使用dmesg | grep acpi

dmesg |egrep -i ''(apm|acpi)''

Kernel command line: vga=274 quiet console=ttyS3,9600acpi=no-idleoot=/dev/hda3

ACPI: Core Subsystem version [20010208]

ACPI: Subsystem enabled

ACPI: System firmware supports: C2

ACPI: plvl2lat=99 plvl3lat=1001

ACPI: C2 enter=1417 C2 exit=354

ACPI: C3 enter=-1 C3 exit=-1

ACPI: Not using ACPI idle

ACPI: System firmware supports: S0 S1 S4 S5

扩展阅读二：dmesg命令使用示例

使用示例

示例一 将开机信息发邮件

man dmesg 写道
The program helps users to print out their bootup messages. Instead of copying the messages by hand, the user need only:

dmesg > boot.messages

and mail the boot.messages file to whoever
can debug their problem.

[root@new55 ~]# dmesg >boot.messages

[root@new55 ~]# ls -l boot.messages 

-rw-r--r-- 1 root root 15838 12-09 12 begin_of_the_skype_highlighting 15838
12-09 12 免费  end_of_the_skype_highlighting:55 boot.messages

[root@new55 ~]# mail -s "Boot Log of Linux Server" public@web3q.NET <boot.messages 

[root@new55 ~]#

示例二 浏览dmesg输出的信息

[root@new55 ~]# uname -a
linux new55 2.6.18-194.el5 #1 SMP Tue Mar 16 21:52:43 EDT 2010 i686 i686
i386 GNU/Linux

[root@new55 ~]# dmesg | less

Linux version 2.6.18-194.el5 (mockbuild@x86-007.build.bos.redhat.com) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)) #1 SMP Tue Mar 16 21:52:43 EDT 2010

BIOS-provided physical RAM map:

 BIOS-e820: 0000000000010000 - 000000000009fc00 (usable)

 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)

 BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)

 BIOS-e820: 0000000000100000 - 000000001f7d0000 (usable)

 BIOS-e820: 000000001f7d0000 - 000000001f7efc00 (reserved)

 BIOS-e820: 000000001f7efc00 - 000000001f7fb000 (ACPI NVS)

 BIOS-e820: 000000001f7fb000 - 000000001f800000 (reserved)

 BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)

 BIOS-e820: 00000000fec00000 - 00000000fec02000 (reserved)

 BIOS-e820: 00000000fed20000 - 00000000fed9b000 (reserved)

 BIOS-e820: 00000000feda0000 - 00000000fedc0000 (reserved)

 BIOS-e820: 00000000ffb00000 - 00000000ffc00000 (reserved)

 BIOS-e820: 00000000fff00000 - 0000000100000000 (reserved)

0MB HIGHMEM available.

503MB LOWMEM available.

Memory for crash kernel (0x0 to 0x0) notwithin permissible range

disabling kdump

Using x86 segment limits to approximate NX protection

On node 0 totalpages: 128976

  DMA zone: 4096 pages, LIFO batch:0

  Normal zone: 124880 pages, LIFO batch:31

DMI 2.3 present.

Using APIC driver default

ACPI: RSDP (v000 HP                                    ) @ 0x000fe270

ACPI: RSDT (v001 HP     30C4     0x31100620 HP   0x00000001) @ 0x1f7efc84

ACPI: FADT (v002 HP     30C4     0x00000002 HP   0x00000001) @ 0x1f7efc00

ACPI: MADT (v001 HP     30C4     0x00000001 HP   0x00000001) @ 0x1f7efcb8

ACPI: MCFG (v001 HP     30C4     0x00000001 HP   0x00000001) @ 0x1f7efd14

ACPI: SSDT (v001 HP       HPQPpc 0x00001001 MSFT 0x0100000e) @ 0x1f7f6698

ACPI: DSDT (v001 HP       DAU00  0x00010000 MSFT 0x0100000e) @ 0x00000000

ACPI: PM-Timer IO Port: 0x1008

ACPI: Local APIC address 0xfec01000

ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled)

Processor #0 6:13 APIC version 20

ACPI: LAPIC_NMI (acpi_id[0x01] high edge lint[0x1])

ACPI: IOAPIC (id[0x01] address[0xfec00000] gsi_base[0])

IOAPIC[0]: apic_id 1, version 32, address 0xfec00000, GSI 0-23

:

示例三 查看dmesg尾部的信息

[root@new55 ~]# dmesg | tail

Bluetooth: L2CAP ver 2.8

Bluetooth: L2CAP socket layer initialized

Bluetooth: RFCOMM socket layer initialized

Bluetooth: RFCOMM TTY layer initialized

Bluetooth: RFCOMM ver 1.8

Bluetooth: HIDP (Human Interface Emulation) ver 1.1

eth0: no IPv6 routers present

Installing knfsd (copyright (C) 1996 okir@monad.swb.de).

NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state recovery directory

NFSD: starting 90-second grace period

[root@new55 ~]#

示例四 安装SS7卡驱动时的内核日志

[root@localhost ss7dpklnx]# cd SS7HD_DRIVER/

[root@localhost SS7HD_DRIVER]# ls

bbdddlnx_iss.h  bbd_hbi.h  bbd_ioc.c  bbd_isr.c  bbd_pci.c  BSD_license.txt  GPL_V2-only_license.txt  install_ss7hd.sh  Makefile26

bbd_def.h       bbd_hs.c   bbd_ioc.h  bbd_lnx.c  bbd_pro.h  build_ss7hd.sh   i21555.h                 Makefile24

[root@localhost SS7HD_DRIVER]# ./build_ss7hd.sh 

make: Entering directory `/usr/src/kernels/2.6.9-22.EL-i686'

  CC [M]  /root/setup/ss7dpklnx/SS7HD_DRIVER/bbd_hs.o

  CC [M]  /root/setup/ss7dpklnx/SS7HD_DRIVER/bbd_ioc.o

  CC [M]  /root/setup/ss7dpklnx/SS7HD_DRIVER/bbd_isr.o

  CC [M]  /root/setup/ss7dpklnx/SS7HD_DRIVER/bbd_pci.o

  CC [M]  /root/setup/ss7dpklnx/SS7HD_DRIVER/bbd_lnx.o

  LD [M]  /root/setup/ss7dpklnx/SS7HD_DRIVER/ss7hddvr26.o

  Building modules, stage 2.

  MODPOST

  CC      /root/setup/ss7dpklnx/SS7HD_DRIVER/ss7hddvr26.mod.o

  LD [M]  /root/setup/ss7dpklnx/SS7HD_DRIVER/ss7hddvr26.ko

make: Leaving directory `/usr/src/kernels/2.6.9-22.EL-i686'http://www.linuxso.com/command/dmesg.html

[root@localhost SS7HD_DRIVER]# ./install_ss7hd.sh 

[root@localhost SS7HD_DRIVER]# lsmod | grep ss7

ss7hddvr26             25808  0

[root@localhost SS7HD_DRIVER]# dmesg | tail

ACPI: PCI interrupt 0000:02:0d.0[?] -> GSI 9 (level, low) -> IRQ 9

BBD[0] 64bit

SS7HD[0] - suspend

Dialogic SS7HD Device Driver V100.00 (Source V1.21)

Copyright (C) Dialogic Corporation 2003-2010.  All Rights Reserved

Using major device number 251.

ACPI: PCI interrupt 0000:02:0d.0[?] -> GSI 9 (level, low) -> IRQ 9

BBD[0] 64bit

[root@localhost SS7HD_DRIVER]# ./install_ss7hd.sh remove

[root@localhost SS7HD_DRIVER]# lsmod | grep ss7

[root@localhost SS7HD_DRIVER]# dmesg | tail

BBD[0] 64bit

SS7HD[0] - suspend

Dialogic SS7HD Device Driver V100.00 (Source V1.21)

Copyright (C) Dialogic Corporation 2003-2010.  All Rights Reserved

Using major device number 251.

ACPI: PCI interrupt 0000:02:0d.0[?] -> GSI 9 (level, low) -> IRQ 9

BBD[0] 64bit

SS7HD[0] - suspend

[root@localhost SS7HD_DRIVER]#

示例五 打印并清除内核环形缓冲区

[root@new55 ~]# dmesg -c

Linux version 2.6.18-194.el5 (mockbuild@x86-007.build.bos.redhat.com) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)) #1 SMP Tue Mar 16 21:52:43 EDT 2010

BIOS-provided physical RAM map:

 BIOS-e820: 0000000000010000 - 000000000009fc00 (usable)

 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)

 BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)

 BIOS-e820: 0000000000100000 - 000000001f7d0000 (usable)

 BIOS-e820: 000000001f7d0000 - 000000001f7efc00 (reserved)

 BIOS-e820: 000000001f7efc00 - 000000001f7fb000 (ACPI NVS)

 BIOS-e820: 000000001f7fb000 - 000000001f800000 (reserved)

 BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)

 BIOS-e820: 00000000fec00000 - 00000000fec02000 (reserved)

 BIOS-e820: 00000000fed20000 - 00000000fed9b000 (reserved)

 BIOS-e820: 00000000feda0000 - 00000000fedc0000 (reserved)

 BIOS-e820: 00000000ffb00000 - 00000000ffc00000 (reserved)

 BIOS-e820: 00000000fff00000 - 0000000100000000 (reserved)

0MB HIGHMEM available.

503MB LOWMEM available.

Memory for crash kernel (0x0 to 0x0) notwithin permissible range

disabling kdump

Using x86 segment limits to approximate NX protection

On node 0 totalpages: 128976

  DMA zone: 4096 pages, LIFO batch:0

  Normal zone: 124880 pages, LIFO batch:31

DMI 2.3 present.

省略输出

Bluetooth: HIDP (Human Interface Emulation) ver 1.1

eth0: no IPv6 routers present

Installing knfsd (copyright (C) 1996 okir@monad.swb.de).

NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state recovery directory

NFSD: starting 90-second grace period

[root@new55 ~]# dmesg

[root@new55 ~]# less /var/log/dmesg

Linux version 2.6.18-194.el5 (mockbuild@x86-007.build.bos.redhat.com) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)) #1 SMP Tue Mar 16 21:52:43 EDT 2010

BIOS-provided physical RAM map:

 BIOS-e820: 0000000000010000 - 000000000009fc00 (usable)

 BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)

 BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)

 BIOS-e820: 0000000000100000 - 000000001f7d0000 (usable)

 BIOS-e820: 000000001f7d0000 - 000000001f7efc00 (reserved)

 BIOS-e820: 000000001f7efc00 - 000000001f7fb000 (ACPI NVS)

 BIOS-e820: 000000001f7fb000 - 000000001f800000 (reserved)

 BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)

 BIOS-e820: 00000000fec00000 - 00000000fec02000 (reserved)

 BIOS-e820: 00000000fed20000 - 00000000fed9b000 (reserved)

 BIOS-e820: 00000000feda0000 - 00000000fedc0000 (reserved)

 BIOS-e820: 00000000ffb00000 - 00000000ffc00000 (reserved)

 BIOS-e820: 00000000fff00000 - 0000000100000000 (reserved)

0MB HIGHMEM available.

503MB LOWMEM available.

Memory for crash kernel (0x0 to 0x0) notwithin permissible range

disabling kdump

Using x86 segment limits to approximate NX protection

On node 0 totalpages: 128976

  DMA zone: 4096 pages, LIFO batch:0

  Normal zone: 124880 pages, LIFO batch:31

DMI 2.3 present.

Using APIC driver default

ACPI: RSDP (v000 HP                                    ) @ 0x000fe270

ACPI: RSDT (v001 HP     30C4     0x31100620 HP   0x00000001) @ 0x1f7efc84

ACPI: FADT (v002 HP     30C4     0x00000002 HP   0x00000001) @ 0x1f7efc00

ACPI: MADT (v001 HP     30C4     0x00000001 HP   0x00000001) @ 0x1f7efcb8

ACPI: MCFG (v001 HP     30C4     0x00000001 HP   0x00000001) @ 0x1f7efd14

ACPI: SSDT (v001 HP       HPQPpc 0x00001001 MSFT 0x0100000e) @ 0x1f7f6698

ACPI: DSDT (v001 HP       DAU00  0x00010000 MSFT 0x0100000e) @ 0x00000000

ACPI: PM-Timer IO Port: 0x1008

ACPI: Local APIC address 0xfec01000

ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled)

Processor #0 6:13 APIC version 20

ACPI: LAPIC_NMI (acpi_id[0x01] high edge lint[0x1])

ACPI: IOAPIC (id[0x01] address[0xfec00000] gsi_base[0])

IOAPIC[0]: apic_id 1, version 32, address 0xfec00000, GSI 0-23

[root@new55 ~]#

http://www.linuxso.com/command/dmesg.html

[ARM-Linux开发]linux dmesg命令参数及用法详解(linux显示开机信息命令)的更多相关文章

  1. linux dmesg命令参数及用法详解(linux显示开机信息命令)

    linux dmesg命令参数及用法详解(linux显示开机信息命令) http://blog.csdn.net/zhongyhc/article/details/8909905 功能说明:显示开机信 ...

  2. linux useradd(adduser)命令参数及用法详解(linux创建新用户命令)

    linux useradd(adduser)命令参数及用法详解(linux创建新用户命令) useradd可用来建立用户帐号.帐号建好之后,再用passwd设定帐号的密码．而可用userdel删除帐号 ...

  3. (转)linux traceroute命令参数及用法详解--linux跟踪路由命令

    linux traceroute命令参数及用法详解--linux跟踪路由命令 原文:http://blog.csdn.net/liyuan_669/article/details/25362505 通 ...

  4. linux scp命令参数及用法详解--linux远程复制拷贝命令使用实例【转】

    转自:http://blog.csdn.net/jiangkai_nju/article/details/7338177 一般情况,本地网络跟远程网络进行数据交抱,或者数据迁移,常用的有三种方法,一是 ...

  5. Linux fdisk命令参数及用法详解---Linux磁盘分区管理命令fdisk

    fdisk 命令 linux磁盘分区管理 用途:观察硬盘之实体使用情形与分割硬盘用. 使用方法: 一.在 console 上输入 fdisk -l /dev/sda ,观察硬盘之实体使用情形. 二.在 ...

  6. Linux quota命令参数及用法详解---Linux磁盘配额限制设置和查看命令

    功能说明:显示磁盘已使用的空间与限制. 语 法:quota [-quvV][用户名称...] 或 quota [-gqvV][群组名称...] 补充说明:执行quota指令,可查询磁盘空间的限制,并得 ...

  7. linux ar命令参数及用法详解--linux建立、修改或抽取备存文件命

    功能说明:建立或修改备存文件,或是从备存文件中抽取文件. 语 法:ar[-dmpqrtx][cfosSuvV][a<成员文件>][b<成员文件>][i<成员文件>] ...

  8. linux modprobe命令参数及用法详解--linux加载模块命令

    转:http://www.linuxso.com/command/modprobe.html modprobe(module probe) 功能说明:自动处理可载入模块. 语 法:modprobe [ ...

  9. linux crontab命令参数及用法详解--linux自动化定时任务cron

    声明:本文转自Linux 安全网,在此基础上加上自己的体会! crontab 命令 如果发现您的系统里没有这个命令,在ubuntu server 中用的是 sudo apt-get install c ...

随机推荐

  1. 利用pil库处理图像

    1关于PIL PIL(Python Image Library)是python的第三方图像处理库,但是由于其强大的功能与众多的使用人数,几乎已经被认为是python官方图像处理库了. 2PIL的主要功 ...

  2. Python bytes类型及用法

    bytes 类型 Python 3 新增了 bytes 类型,用于代表字节串,是一个类型,不是C#中的列表. 字符串(str)由多个字符组成,以字符为单位进行操作: 字节串(bytes)由多个字节组成 ...

  3. windows下的批处理bat文件和Linux下的shell文件的互相转换

    shell(Linux.Solaris) bat(windows) 含义 # rem 注释行 /[directory]/[directory]/.../[directory]/ [disk]:\[di ...

  4. NSKeyedArchiver : NSCoder

    NSKeyedArchiver : NSCoder @interface NSData : NSObject <NSCopying, NSMutableCopying, NSSecureCodi ...

  5. （知识点1）#pragma once 与 #ifndef 解析

    例如 为了避免同一个文件被include多次,C/C++中有两种方式,一种是#ifndef方式,一种是#pragma once方式.在能够支持这两种方式的编译器上,二者并没有太大的区别,但是两者仍然还 ...

  6. CentOS7 配置阿里云yum源,vim编辑器，tab自动补全

    1.进入yum的文件夹 命令:cd   /etc/yum.repos.d/ 2.下载wget 命令:yum -y install wget 3.删除yum文件夹所有yum源 命令:rm -rf    ...

  7. -bash: rvictls: command not found

    下载安装Command Line Tools for Xcodehttps://developer.apple.com/download/more/?name=for%20Xcode%20-# 显示包 ...

  8. lintcode-720重排带整数字符串

    题目描述: 给一包含大写字母和整数(从 0 到 9)的字符串, 试写一函数返回有序的字母以及数字和. 样例 给出 str = AC2BEW3, 返回 ABCEW5字母按字母表的顺序排列, 接着是整数的 ...

  9. 使用helm进行kubernetes包管理

    1. 安装helm package https://github.com/helm/helm/blob/master/LICENSE 2. 将 helm 配置到环境变量 3. 使用helm的前提是安装 ...

  10. 【转】linux sed命令

    转自:linux sed命令就是这么简单 参考:Linux三大剑客之sed:https://blog.csdn.net/solaraceboy/article/details/79272344 阅读目 ...