| 1 | dmesg
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| 2 | ===
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| 3 |
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| 4 | 显示Linux系统启动信息
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| 5 |
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| 6 | ## 补充说明
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| 7 |
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| 8 | **dmesg命令** 被用于检查和控制内核的环形缓冲区。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。开机信息保存在`/var/log/dmesg`文件里。
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| 9 |
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| 10 | ### 语法
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| 11 |
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| 12 | ```shell
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| 13 | dmesg(选项)
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| 14 | ```
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| 15 |
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| 16 | ### 选项
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| 17 |
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| 18 | ```shell
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| 19 | -c：显示信息后，清除ring buffer中的内容；
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| 20 | -s<缓冲区大小>：预设置为8196，刚好等于ring buffer的大小；
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| 21 | -n：设置记录信息的层级。
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| 22 | ```
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| 23 |
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| 24 | ### 实例
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| 25 |
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| 26 | ```shell
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| 27 | [root@localhost ~]# dmesg | head
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| 28 | Linux version 2.6.18-348.6.1.el5 (mockbuild@builder17.centos.org) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-54)) #1 SMP Tue May 21 15:34:22 EDT 2013
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| 29 | BIOS-provided physical RAM map:
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| 30 | BIOS-e820: 0000000000010000 - 000000000009f400 (usable)
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| 31 | BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
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| 32 | BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
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| 33 | BIOS-e820: 0000000000100000 - 000000007f590000 (usable)
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| 34 | BIOS-e820: 000000007f590000 - 000000007f5e3000 (ACPI NVS)
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| 35 | BIOS-e820: 000000007f5e3000 - 000000007f5f0000 (ACPI data)
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| 36 | BIOS-e820: 000000007f5f0000 - 000000007f600000 (reserved)
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| 37 | BIOS-e820: 00000000e0000000 - 00000000e8000000 (reserved)
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| 38 | ```
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| 39 |
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| 40 | 查看硬盘基础信息
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| 41 |
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| 42 | ```shell
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| 43 | dmesg | grep sda
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| 44 |
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| 45 | [ 2.442555] sd 0:0:0:0: [sda] 488281250 512-byte logical blocks: (250 GB/232 GiB)
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| 46 | [ 2.442590] sd 0:0:0:0: [sda] Write Protect is off
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| 47 | [ 2.442592] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
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| 48 | [ 2.442607] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
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| 49 | [ 2.447533] sda: sda1
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| 50 | [ 2.448503] sd 0:0:0:0: [sda] Attached SCSI disk
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| 51 | ```
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| 52 |
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| 53 |
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