dmesg 命令可显示系统开机信息，一般用于故障排查和设备/驱动的加载的查询。
在日常工作中，dmesg 命令曾被用于查看硬盘加载状况：
root@ubuntu:~/Desktop# dmesg | grep sda [ 3.791441] sd 32:0:0:0: [sda] 83886080 512-byte logical blocks: (42.9 GB/40.0 GiB) [ 3.791536] sd 32:0:0:0: [sda] Write Protect is off [ 3.791539] sd 32:0:0:0: [sda] Mode Sense: 61 00 00 00 [ 3.791740] sd 32:0:0:0: [sda] Cache data unavailable [ 3.791742] sd 32:0:0:0: [sda] Assuming drive cache: write through [ 3.792287] sd 32:0:0:0: [sda] Cache data unavailable [ 3.792289] sd 32:0:0:0: [sda] Assuming drive cache: write through [ 3.869834] sda: sda1 sda2 < sda5 > [ 3.877637] sd 32:0:0:0: [sda] Cache data unavailable [ 3.877641] sd 32:0:0:0: [sda] Assuming drive cache: write through [ 3.877644] sd 32:0:0:0: [sda] Attached SCSI disk [ 5.873666] EXT4-fs (sda1): INFO: recovery required on readonly filesystem [ 5.873670] EXT4-fs (sda1): write access will be enabled during recovery [ 17.943579] EXT4-fs (sda1): recovery complete [ 18.091471] EXT4-fs (sda1): mounted filesystem with ordered data mode. Opts: (null) [ 48.693907] Adding 1046524k swap on /dev/sda5. Priority:-1 extents:1 across:1046524k [ 49.938769] EXT4-fs (sda1): re-mounted. Opts: errors=remount-ro
也可用于查看硬件加载情况，比如查看 can 口的接入情况：
# dmesg | grep can [605149.652926] c_can_platform 481cc000.d_can can0: setting BTR=1c05 BRPE=0000 [614575.355562] c_can_platform 481cc000.d_can can0: setting BTR=1c05 BRPE=0000 [634483.860545] c_can_platform 481cc000.d_can can0: setting BTR=1c05 BRPE=0000
查看 usb 接入情况：
root@ubuntu:~/桌面# dmesg | grep usb [ 2.268915] usbcore: registered new interface driver usbfs [ 2.268951] usbcore: registered new interface driver hub [ 2.269264] usbcore: registered new device driver usb [ 2.912961] usbcore: registered new interface driver libusual [ 3.222047] usb 2-1: new full-speed USB device number 2 using uhci_hcd [ 3.488637] usb 2-2: new full-speed USB device number 3 using uhci_hcd
因此 dmesg 命令是一个检测系统设备接入状态、排查系统故障的很方便的命令工具。
若需要查看所有信息，可执行
dmesg > dmesg.txt
将命令打印信息保存成 dmesg.txt 文件供查阅。