昨天推荐：每天学一个Linux命令（42）：unzip命令介绍dmesg命令用于显示系统启动信息，可用于诊断系统故障.内核会将系统启动信息存放在环形缓冲区中，可以使用dmesg命令查看，启动信息保存在/var/log/dmesg文件中。命令语法dmesg[options]选项说明-c#显示信息后，清空ringbuffer中的内容-s#默认值为8196，正好等于ringbuffer的大小-n#设置记录信息的级别-D#禁止向控制台打印消息-E#允许向控制台打印消息-h#打印帮助文本并退出-k#打印内核消息-n#设置向控制台打印消息的级别-r#Printrawmessagebuffer-s#使用多少个缓冲区来查询内核环缓冲区。16392bydefault-T#printhuman-readabletimestamp-t#donotprintkernel'stimestamp-u#printuserspacemessage-V#outputversioninfoandexit-x#numberfacilityandlevel(priority)解码为可读的前缀应用举例查看前20行开机信息[root@centos7?~]#?dmesg?|?head?-n?20[????0.000000]?Initializing?cgroup?subsys?cpuset[????0.000000]?Initializing?cgroup?subsys?cpu[????0.000000]?Initializing?cgroup?subsys?cpuacct[????0.000000]Linuxversion3.10.0-1127.18.2.el7.x86_64(mockbuild@kbuilder.bsys.centos.org)(gccversion4.8.520150623(RedHat4.8.5-39)(GCC))#1SMPSunJul2615:27:06UTC2020[0.000000]Commandline:BOOT_IMAGE=/vmlinuz-3.10.0-1127.18.2.el7.x86_64root=/dev/mapper/centos-rootrocrashkernel=autospectre_v2=retpolinerd.lvm.lv=centos/rootrd.lvm.lv=centos/swaprhgbquietLANG=en_US.UTF-8[0.000000]Disabledfaststringoperations[0.000000]e820:BIOS-providedphysicalRAMmap:[0.000000]2BIOS-[mem0x0000000000000000-0x0000000000009ebff]usable[0.000000]BIOS-e820:[mem0x000000000009ec00-0x000000000009ffff]reserved[0.000000]BIOS-e820820:?[mem?0x00000000000dc000-0x00000000000fffff]?reserved[????0.000000]?BIOS-e820:?[mem?0x0000000000100000-0x000000003fedffff]?usable[????0.000000]?BIOS-e820:?[mem?0x000000003fee0000-0x000000003fefefff]?ACPI?data[????0.000000]?BIOS-e820:?[mem?0x000000003feff000-0x000000003fefffff]?ACPI?NVS[????0.000000]?BIOS-e820:?[mem?0x000000003ff00000-0x000000003fffffff]?usable[????0.000000]?BIOS-e820:?[mem?0x00000000f0000000-0x00000000f7ffffff]?reserved[????0.000000]?BIOS-e820:?[mem?0x00000000fec00000-0x00000000fec0ffff]?reserved[????0.000000]?BIOS-e820:?[mem?0x00000000fee00000-0x00000000fee00fff]?reserved[????0.000000]?BIOS-e820:?[mem?0x00000000fffe0000-0x00000000ffffffff]?reserved[????0.000000]?NX?(Execute?Disable)?protection:?active[????0.000000]?SMBIOS?2.4?present.查看与内存相关的开机信息[root@centos7~]#dmesg|grep-i内存[0.000000]基本内存蹦床在[ffff9102c0098000]98000大小24576[0.000000]crashkernel=auto导致保留的零字节内存。[0.000000]早期内存节点范围[0.000000]PM：注册的nosave内存：[MEM0x0009E000-0X0009EFF][0.000000][0.000000]PM：注册的nosave存储器：[MEM0X0009F000-0X000-0X0009FFFF]0x000A0000-0X000DBFFF][0.000000]PM：注册的NoSave内存：[MEM0X000DC000-0X000FFFFF][0.000000][0.000000][0.000000]PM：注册的nosave存储器：[MEM0X3FEE00-0X3FEE00-0X3FEFEFFFF]0.000000]内存：972140K/1048576K可用（7784K内核代码，524K不存在，75912K保留，5958K数据，1980KINIT）[0.000000init）[0.000000]请尝试尝试'cgroup_disable=内存=记忆'如果不需要内存cgroupscgroups[0.75555555555555555555555555555555555555528]内存[1.619645]x86/mm：内存块大小：128MB[3.669071]释放intrd内存：20628K释放[3.933907]非挥发性存储器驱动程序v1.3[3.935079]崩溃存储器驱动程序崩溃驱动程序：1.1[4.000261]版本1.1[4.000261]ernel?memory:?1980k?freed[????4.001692]?Freeing?unused?kernel?memory:?396k?freed[????4.003171]?Freeing?unused?kernel?memory:?540k?freed[????5.956205]?[drm]?Max?dedicated?hypervisor?surface?memory?is?0?kiB[????5.956206]?[drm]?Maximum?display?memory?size?is32768kiB[5.968934][TTM]区域内核：可用图形内存：497842kiB查看与磁盘相关的开机信息[root@centos7~]#dmesg|GREP-I磁盘[0.000000]RAMDISK：[MEM0x357A7000-0X36BCBFFF][3.738914]VFS：磁盘配额DQUOT_6.5.2[4.0133333]Systemd[1]:[sda]附加的SCSI磁盘[root@centos7~]#dmesg|grep-isda[6.291698]sd0:0:0:0:[sda]41943040512字节逻辑块：(21.4GB/20.0GiB)[6.291830]sd0:0:0:0:[sda]写保护关闭[6.291831]sd0:0:0:0:[sda]模式感知：61000000[6.292032]sd0:0:0:0:[sda]缓存数据不可用[6.292033]sd0:0:0:0：[sda]假设驱动器缓存：写入[6.294046]sda:sda1sda2[6.295432]sd0:0:0:0:[sda]附加的SCSI磁盘[15.843965]XFS(sda1):挂载V5文件系统[16.778908]XFS(sda1):开始恢复(logdev)90intern16。XFS(sda1):结束恢复(logdev:internal)每天学一个Linux命令(39):tar每天学一个Linux命令(40):gzip每天学一个Linux命令(41):zip
