我使用过的Linux命令之dmesg - 查看开机信息/打印或控制内核环形缓冲区

本文链接：http://codingstandards.iteye.com/blog/837486 ??? （转载请注明出处）

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用途说明

dmesg命令用于打印Linux系统开机启动信息，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（print or control the kernel ring buffer）。开机信息亦保存在/var/log/dmesg的文件里。某些硬件设备（比如七号信令卡、语音卡之类）在安装的时候，通常会安装驱动程序（内核模块），会打印一些信息，就可以通过dmesg命令来查看。

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常用参数

格式：dmesg

查看开机信息。

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格式：dmesg -c

清除开机信息，但/var/log/dmesg文件中仍然有这些信息。

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因为dmesg命令输出的东西有点多，通常与less/more/tail/grep等命令配合使用。

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使用示例

示例一 将开机信息发邮件

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[root@new55 ~]# dmesg >boot.messages

[root@new55 ~]# ls -l boot.messages
-rw-r--r-- 1 root root 15838 12-09 12:55 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
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示例三 查看dmesg尾部的信息