dmesg 可以查看Linux 内核引导相关的所有信息

dmesg’命令设备故障的诊断是非常重要的。在‘dmesg’命令的帮助下进行硬件的连接或断开连接操作时，我们可以看到硬件的检测或者断开连接的信息。‘dmesg’命令在多数基于Linux和Unix的操作系统中都可以使用。

列出加载到内核中的所有驱动

我们可以使用如‘more’。 ‘tail’, ‘less ’或者‘grep’文字处理工具来处理‘dmesg’命令的输出。由于dmesg日志的输出不适合在一页中完全显示，因此我们使用管道（pipe）将其输出送到more或者less命令单页显示。

 [root@hanyw-Bash-Python ten-command-performance]# dmesg | more
[    0.000000] Linux version 5.14.0-402.el9.x86_64 (mockbuild@x86-05.stream.rdu2.redhat.com) (gcc (GCC) 11.4.1 2023060
5 (Red Hat 11.4.1-2), GNU ld version 2.35.2-42.el9) #1 SMP PREEMPT_DYNAMIC Thu Dec 21 19:46:35 UTC 2023
[    0.000000] The list of certified hardware and cloud instances for Red Hat Enterprise Linux 9 can be viewed at the 
Red Hat Ecosystem Catalog, https://catalog.redhat.com.
[    0.000000] Command line: BOOT_IMAGE=(hd0,msdos1)/vmlinuz-5.14.0-402.el9.x86_64 root=/dev/mapper/cs-root ro rd.lvm.
lv=cs/root
[    0.000000] Disabled fast string operations
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    0.000000] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'compacted' format.
[    0.000000] signal: max sigframe size: 1776
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009ebff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009ec00-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000dc000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000007fedffff] usable
[    0.000000] BIOS-e820: [mem 0x000000007fee0000-0x000000007fefefff] ACPI data
[    0.000000] BIOS-e820: [mem 0x000000007feff000-0x000000007fefffff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000007ff00000-0x000000007fffffff] 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 2.7 present.
[    0.000000] DMI: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
[    0.000000] vmware: hypercall mode: 0x02
[    0.000000] Hypervisor detected: VMware
[    0.000000] vmware: TSC freq read from hypervisor : 3600.000 MHz
[    0.000000] vmware: Host bus clock speed read from hypervisor : 66000000 Hz
--更多--

如下的指令也是类似的区别。

dmesg | less

输出如下。

[root@hanyw-Bash-Python ten-command-performance]# dmesg | less



[    0.000000] Linux version 5.14.0-402.el9.x86_64 (mockbuild@x86-05.stream.rdu2.redhat.com) (gcc (GCC) 11.4.1 20230605 (Red Hat 11.4.1-2), GNU ld version 2.35.2-42.el9) #1 SMP PREEMPT_DYNAMIC Thu Dec 21 19:46:35 UTC 2023
[    0.000000] The list of certified hardware and cloud instances for Red Hat Enterprise Linux 9 can be viewed at the Red Hat Ecosystem Catalog, https://catalog.redhat.com.
[    0.000000] Command line: BOOT_IMAGE=(hd0,msdos1)/vmlinuz-5.14.0-402.el9.x86_64 root=/dev/mapper/cs-root ro rd.lvm.lv=cs/root
[    0.000000] Disabled fast string operations
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    0.000000] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'compacted' format.
[    0.000000] signal: max sigframe size: 1776
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009ebff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009ec00-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000dc000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000007fedffff] usable
[    0.000000] BIOS-e820: [mem 0x000000007fee0000-0x000000007fefefff] ACPI data
[    0.000000] BIOS-e820: [mem 0x000000007feff000-0x000000007fefffff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000007ff00000-0x000000007fffffff] 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 2.7 present.
[    0.000000] DMI: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
[    0.000000] vmware: hypercall mode: 0x02
[    0.000000] Hypervisor detected: VMware
[    0.000000] vmware: TSC freq read from hypervisor : 3600.000 MHz
[    0.000000] vmware: Host bus clock speed read from hypervisor : 66000000 Hz
[    0.000000] vmware: using clock offset of 26849061647 ns
[    0.000020] tsc: Detected 3600.000 MHz processor
[    0.001616] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved
[    0.001619] e820: remove [mem 0x000a0000-0x000fffff] usable
[    0.001623] last_pfn = 0x80000 max_arch_pfn = 0x400000000
[    0.001642] total RAM covered: 3072M
[    0.001885] Found optimal setting for mtrr clean up
[    0.001886]  gran_size: 64K  chunk_size: 64K         num_reg: 2      lose cover RAM: 0G
[    0.001889] MTRR map: 6 entries (5 fixed + 1 variable; max 21), built from 8 variable MTRRs
[    0.001890] x86/PAT: Configuration [0-7]: WB  WC  UC- UC  WB  WP  UC- WT  
[    0.009247] found SMP MP-table at [mem 0x000f6a70-0x000f6a7f]
:

列出所有被检测到的硬件

要显示所有被内核检测到的硬盘设备，你可以使用‘grep’命令搜索‘sda’关键词，如下

[root@hanyw-Bash-Python ten-command-performance]# dmesg |grep sd[a-z]
[    0.000000] Command line: BOOT_IMAGE=(hd0,msdos1)/vmlinuz-5.14.0-402.el9.x86_64 root=/dev/mapper/cs-root ro rd.lvm.lv=cs/root
[    0.150022] Kernel command line: BOOT_IMAGE=(hd0,msdos1)/vmlinuz-5.14.0-402.el9.x86_64 root=/dev/mapper/cs-root ro rd.lvm.lv=cs/root
[    0.150061] Unknown kernel command line parameters "BOOT_IMAGE=(hd0,msdos1)/vmlinuz-5.14.0-402.el9.x86_64", will be passed to user space.
[    3.366214]     BOOT_IMAGE=(hd0,msdos1)/vmlinuz-5.14.0-402.el9.x86_64
[    5.559567] sd 2:0:0:0: [sda] 251658240 512-byte logical blocks: (129 GB/120 GiB)
[    5.559645] sd 2:0:0:0: [sda] Write Protect is off
[    5.559647] sd 2:0:0:0: [sda] Mode Sense: 61 00 00 00
[    5.559754] sd 2:0:0:0: [sda] Cache data unavailable
[    5.559755] sd 2:0:0:0: [sda] Assuming drive cache: write through
[    5.569553]  sda: sda1 sda2
[    5.569701] sd 2:0:0:0: [sda] Attached SCSI disk
[   25.628710] XFS (sda1): Mounting V5 Filesystem 33b3fa8b-f02c-409d-afc0-cccd91030610
[   31.721751] XFS (sda1): Ending clean mount

__ 注解 sda 表示第一块 SATA硬盘，sdb表示第二块SATA硬盘。若想查看IDE硬盘搜索hda或hdb关键词。__

只输出dmesg命令的前30行日志

在‘dmesg’命令后跟随‘head’命令来显示开始几行，‘dmesg | head -30′命令将显示开始的前20行

[root@hanyw-Bash-Python ~]# dmesg | head -30
[    0.000000] Linux version 5.14.0-402.el9.x86_64 (mockbuild@x86-05.stream.rdu2.redhat.com) (gcc (GCC) 11.4.1 20230605 (Red Hat 11.4.1-2), GNU ld version 2.35.2-42.el9) #1 SMP PREEMPT_DYNAMIC Thu Dec 21 19:46:35 UTC 2023
[    0.000000] The list of certified hardware and cloud instances for Red Hat Enterprise Linux 9 can be viewed at the Red Hat Ecosystem Catalog, https://catalog.redhat.com.
[    0.000000] Command line: BOOT_IMAGE=(hd0,msdos1)/vmlinuz-5.14.0-402.el9.x86_64 root=/dev/mapper/cs-root ro rd.lvm.lv=cs/root
[    0.000000] Disabled fast string operations
[    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    0.000000] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    0.000000] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'compacted' format.
[    0.000000] signal: max sigframe size: 1776
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009ebff] usable
[    0.000000] BIOS-e820: [mem 0x000000000009ec00-0x000000000009ffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000000dc000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000007fedffff] usable
[    0.000000] BIOS-e820: [mem 0x000000007fee0000-0x000000007fefefff] ACPI data
[    0.000000] BIOS-e820: [mem 0x000000007feff000-0x000000007fefffff] ACPI NVS
[    0.000000] BIOS-e820: [mem 0x000000007ff00000-0x000000007fffffff] 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 2.7 present.
[    0.000000] DMI: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
[    0.000000] vmware: hypercall mode: 0x02
[    0.000000] Hypervisor detected: VMware
[    0.000000] vmware: TSC freq read from hypervisor : 3600.000 MHz
[    0.000000] vmware: Host bus clock speed read from hypervisor : 66000000 Hz
[    0.000000] vmware: using clock offset of 26849061647 ns

只输出dmesg命令最后20行日志

在‘dmesg’命令后跟随‘tail’命令（‘ dmesg | tail -fn20’）来输出‘dmesg’命令的最后20行日志，当你插入可移动设备时它是非常有用的。

[root@hanyw-Bash-Python ~]# dmesg | tail -fn 20
[   25.739895] vmwgfx 0000:00:0f.0: [drm] DMA map mode: Caching DMA mappings.
[   25.740440] vmwgfx 0000:00:0f.0: [drm] Legacy memory limits: VRAM = 4096 kB, FIFO = 256 kB, surface = 0 kB
[   25.740442] vmwgfx 0000:00:0f.0: [drm] MOB limits: max mob size = 262144 kB, max mob pages = 196608
[   25.740444] vmwgfx 0000:00:0f.0: [drm] Max GMR ids is 64
[   25.740445] vmwgfx 0000:00:0f.0: [drm] Max number of GMR pages is 65536
[   25.740446] vmwgfx 0000:00:0f.0: [drm] Maximum display memory size is 262144 kiB
[   25.766524] vmwgfx 0000:00:0f.0: [drm] Screen Target display unit initialized
[   25.770299] vmwgfx 0000:00:0f.0: [drm] Fifo max 0x00040000 min 0x00001000 cap 0x0000077f
[   25.770815] vmwgfx 0000:00:0f.0: [drm] Using command buffers with DMA pool.
[   25.770821] vmwgfx 0000:00:0f.0: [drm] Available shader model: Legacy.
[   25.845914] [drm] Initialized vmwgfx 2.20.0 20211206 for 0000:00:0f.0 on minor 0
[   25.852749] fbcon: vmwgfxdrmfb (fb0) is primary device
[   25.853553] Console: switching to colour frame buffer device 160x50
[   25.856173] vmwgfx 0000:00:0f.0: [drm] fb0: vmwgfxdrmfb frame buffer device
[   31.721751] XFS (sda1): Ending clean mount
[   36.632583] NET: Registered PF_VSOCK protocol family
[   47.484728] Warning: Unmaintained driver is detected: ip_set
[   47.484730] Warning: Deprecated Driver is detected: ip_set will not be maintained in a future major release and may be disabled
[   47.694148] vmxnet3 0000:03:00.0 ens160: intr type 3, mode 0, 2 vectors allocated
[   47.694537] vmxnet3 0000:03:00.0 ens160: NIC Link is Up 10000 Mbps

由于‘dmesg’命令的输出实在太长了，在其中搜索某个特定的字符串是非常困难的。因此，有必要过滤出一些包含‘usb’ ‘dma’ ‘tty’ ‘memory’等字符串的日志行。grep 命令 的‘-i’选项表示忽略大小写

[root@hanyw-Bash-Python ~]# dmesg | grep -i memory
[    0.009403] ACPI: Reserving FACP table memory at [mem 0x7fefee73-0x7fefef66]
[    0.009404] ACPI: Reserving DSDT table memory at [mem 0x7feead55-0x7fefee72]
[    0.009405] ACPI: Reserving FACS table memory at [mem 0x7fefffc0-0x7fefffff]
[    0.009405] ACPI: Reserving FACS table memory at [mem 0x7fefffc0-0x7fefffff]
[    0.009406] ACPI: Reserving BOOT table memory at [mem 0x7feead2d-0x7feead54]
[    0.009406] ACPI: Reserving APIC table memory at [mem 0x7feea5eb-0x7feead2c]
[    0.009407] ACPI: Reserving MCFG table memory at [mem 0x7feea5af-0x7feea5ea]
[    0.009407] ACPI: Reserving SRAT table memory at [mem 0x7fee9757-0x7fee9ffe]
[    0.009408] ACPI: Reserving HPET table memory at [mem 0x7fee971f-0x7fee9756]
[    0.009408] ACPI: Reserving WAET table memory at [mem 0x7fee96f7-0x7fee971e]
[    0.009720] Early memory node ranges
[    0.026936] PM: hibernation: Registered nosave memory: [mem 0x00000000-0x00000fff]
[    0.026938] PM: hibernation: Registered nosave memory: [mem 0x0009e000-0x0009efff]
[    0.026938] PM: hibernation: Registered nosave memory: [mem 0x0009f000-0x0009ffff]
[    0.026939] PM: hibernation: Registered nosave memory: [mem 0x000a0000-0x000dbfff]
[    0.026939] PM: hibernation: Registered nosave memory: [mem 0x000dc000-0x000fffff]
[    0.026940] PM: hibernation: Registered nosave memory: [mem 0x7fee0000-0x7fefefff]
[    0.026941] PM: hibernation: Registered nosave memory: [mem 0x7feff000-0x7fefffff]
[    0.175052] Memory: 260860K/2096628K available (16384K kernel code, 5616K rwdata, 11640K rodata, 3872K init, 6008K bss, 156564K reserved, 0K cma-reserved)
[    0.697805] x86/mm: Memory block size: 128MB
[    1.961405] Non-volatile memory driver v1.3
[    2.915414] Freeing initrd memory: 35840K
[    3.269535] Freeing unused decrypted memory: 2028K
[    3.270606] Freeing unused kernel image (initmem) memory: 3872K
[    3.273128] Freeing unused kernel image (rodata/data gap) memory: 648K
[   25.740440] vmwgfx 0000:00:0f.0: [drm] Legacy memory limits: VRAM = 4096 kB, FIFO = 256 kB, surface = 0 kB
[   25.740446] vmwgfx 0000:00:0f.0: [drm] Maximum display memory size is 262144 kiB

显示时间戳

使用dmesg -T可以显示对应事件的时间戳。

人性化显示

使用dmesg -H指令，人性化显示信息，如下图所示。

过滤系统初始化时的错误信息

服务器在初始化启动和启动后运行的一段时间内，如果有对应的报错，会将报错信息进行收集，然后通过dmesg指令可以查看，如下。

[root@hanyw-Bash-Python ~]# dmesg -T |grep  -i 'error\|fail\|warn'
[一 1月 29 16:25:04 2024] pci 0000:00:15.3: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.4: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.5: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.6: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.7: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.3: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.4: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.5: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.6: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.7: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.3: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.4: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.5: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.6: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.7: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.2: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.3: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.4: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.5: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.6: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.7: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.7: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.6: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.5: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.4: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.3: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:18.2: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.7: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.6: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.5: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.4: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:17.3: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.7: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.6: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.5: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.4: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:16.3: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.7: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.6: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.5: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.4: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:04 2024] pci 0000:00:15.3: BAR 13: failed to assign [io  size 0x1000]
[一 1月 29 16:25:08 2024] Warning: Unmaintained driver is detected: mptbase
[一 1月 29 16:25:08 2024] Warning: Unmaintained driver is detected: mptscsih
[一 1月 29 16:25:08 2024] Warning: Unmaintained driver is detected: mptspi
[一 1月 29 16:25:50 2024] Warning: Unmaintained driver is detected: ip_set
[一 1月 29 16:25:50 2024] Warning: Deprecated Driver is detected: ip_set will not be maintained in a future major release and may be disabled