Linux命令（23）：demsg命令-显示开机信息
demsg命令
功能说明
demsg命令用于显示开机信息，内核会将开机信息存储在系统缓冲区（ring buffer）中，开机后可用dmesg命令查看，也可以在/var/log/目录中查看dmesg文件。用法如下：
| dmesg [选项] |
命令参数
| 选项 | 含义 |
| -c | 显示开机信息后，清除ring buffer信息 |
| -s | 设置缓冲区大小，默认设置为8192 |
| -n | 设置记录信息的层级 |
内核缓冲区的信息对于诊断系统非常有用。在查看时可以配合grep使用。
示例
使用tail查看最后10条信息
[root@c7 ~]# dmesg | tail [ 14.173511] Ebtables v2.0 registered [ 14.211151] Bridge firewalling registered [ 15.018274] IPv6: ADDRCONF(NETDEV_UP): eno16777736: link is not ready [ 15.023187] e1000: eno16777736 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None [ 15.027562] IPv6: ADDRCONF(NETDEV_UP): eno16777736: link is not ready [ 15.027571] IPv6: ADDRCONF(NETDEV_CHANGE): eno16777736: link becomes ready [73937.594566] e1000: eno16777736 NIC Link is Down [74082.150628] e1000: eno16777736 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None [74082.153014] IPv6: ADDRCONF(NETDEV_CHANGE): eno16777736: link becomes ready [102547.555629] perf interrupt took too long (2547 > 2500), lowering kernel.perf_event_max_sample_rate to 50000 |
使用grep查看关于网卡设备的信息
[root@c7 ~]# dmesg | grep eno16 [ 2.834942] systemd-udevd[497]: renamed network interface eth0 to eno16777736 [ 15.018274] IPv6: ADDRCONF(NETDEV_UP): eno16777736: link is not ready [ 15.023187] e1000: eno16777736 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None [ 15.027562] IPv6: ADDRCONF(NETDEV_UP): eno16777736: link is not ready [ 15.027571] IPv6: ADDRCONF(NETDEV_CHANGE): eno16777736: link becomes ready [73937.594566] e1000: eno16777736 NIC Link is Down [74082.150628] e1000: eno16777736 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None [74082.153014] IPv6: ADDRCONF(NETDEV_CHANGE): eno16777736: link becomes ready |
学习自：
高俊峰《循序渐进Linux》
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