dmesg命令手冊(cè)
dmesg：顯示開機(jī)信息
使用dmesg命令可以顯示系統(tǒng)開機(jī)啟動(dòng)信息。
內(nèi)核會(huì)將開機(jī)啟動(dòng)信息存儲(chǔ)在 ring buffer（環(huán)形緩沖區(qū)）中。您若是開機(jī)時(shí)來不及查看信息，可利用dmesg命令來查看。開機(jī)信息保存在 /var/log/dmesg 日志文件里。某些硬件設(shè)備在安裝時(shí)，通常會(huì)安裝驅(qū)動(dòng)程序（內(nèi)核模塊），會(huì)打印一些信息，也可以通過dmesg命令來查看。
命令語法
dmesg [選項(xiàng)]
選項(xiàng)含義
命令中各選項(xiàng)的含義如下表所示。
| 選項(xiàng) | 含義 |
|---|---|
| -c | 顯示信息后，清除環(huán)形緩沖區(qū)中的內(nèi)容 |
| -n <等級(jí)> | 設(shè)置記錄信息的等級(jí) |
| -r | 打印原始消息緩沖區(qū) |
| -s <緩沖區(qū)大小> | 默認(rèn)為8196，剛好等于環(huán)形緩沖區(qū)的大小 |
參考實(shí)例
（1）顯示系統(tǒng)開機(jī)啟動(dòng)信息
[root@cnLinuxer ~]# dmesg
（2）查看硬盤基礎(chǔ)信息
[root@cnLinuxer ~]# dmesg | grep sda
[ 1.720139] sd 2:0:0:0: [sda] 209715200 512-byte logical blocks: (107 GB/100 GiB)
[ 1.720178] sd 2:0:0:0: [sda] Write Protect is off
[ 1.720181] sd 2:0:0:0: [sda] Mode Sense: 61 00 00 00
[ 1.720246] sd 2:0:0:0: [sda] Cache data unavailable
[ 1.720249] sd 2:0:0:0: [sda] Assuming drive cache: write through
[ 1.721667] sda: sda1 sda2
[ 1.722119] sd 2:0:0:0: [sda] Attached SCSI disk
[ 3.871024] XFS (sda1): Mounting V5 Filesystem
[ 3.993830] XFS (sda1): Ending clean mount
（3）查看內(nèi)存基礎(chǔ)信息
[root@cnLinuxer ~]# dmesg | grep memory
[ 0.000000] Base memory trampoline at [ffff91c9c0098000] 98000 size 24576
[ 0.000000] Reserving 161MB of memory at 688MB for crashkernel (System RAM: 2047MB)
[ 0.000000] Early memory node ranges
[ 0.000000] PM: Registered nosave memory: [mem 0x0009e000-0x0009efff]
[ 0.000000] PM: Registered nosave memory: [mem 0x0009f000-0x0009ffff]
[ 0.000000] PM: Registered nosave memory: [mem 0x000a0000-0x000dbfff]
[ 0.000000] PM: Registered nosave memory: [mem 0x000dc000-0x000fffff]
[ 0.000000] PM: Registered nosave memory: [mem 0x7fee0000-0x7fefefff]
[ 0.000000] PM: Registered nosave memory: [mem 0x7feff000-0x7fefffff]
[ 0.000000] please try 'cgroup_disable=memory' option if you don't want memory cgroups
[ 0.149369] Initializing cgroup subsys memory
[ 0.851656] Freeing initrd memory: 21092k freed
[ 0.926515] Non-volatile memory driver v1.3
[ 0.927771] crash memory driver: version 1.1
[ 0.953251] Freeing unused kernel memory: 1980k freed
[ 0.954907] Freeing unused kernel memory: 396k freed
[ 0.956232] Freeing unused kernel memory: 540k freed
[ 1.617861] [drm] Max dedicated hypervisor surface memory is 0 kiB
[ 1.617862] [drm] Maximum display memory size is 131072 kiB
[ 1.617976] [TTM] Zone kernel: Available graphics memory: 931520 kiB
[root@cnLinuxer ~]#
（4）清空dmesg環(huán)形緩沖區(qū)中的日志
[root@cnLinuxer ~]# dmesg -c
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