12.3.1 dmesg日志：记录内核日志信息

12.3.1 dmesg日志：记录内核日志信息

日志文件/var/log/dmesg中记录了系统启动过程中的内核日志信息，包括系统的设备信息，以及在启动和操作过程中系统记录的任何错误和问题的信息。下面是该文件内容的一个截取。

Linux version 2.6.18-92.el5 (brewbuilder@hs20-bc2-3.build.redhat.com) (gcc version 4.1.2 20071124 (Red Hat 4.1.2-41)) #1 SMP Tue Apr
29 13:16:12 EDT 2008
BIOS-provided physical RAM map: // BIOS物理内存匹配
BIOS-e820: 0000000000000000 - 000000000009fc00 (usable) //可用内存
BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) //保留内存
BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 000000001fff0000 (usable)
BIOS-e820: 000000001fff0000 - 000000001fff3000 (ACPI NVS)
BIOS-e820: 000000001fff3000 - 0000000020000000 (ACPI data)
BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved)
0MB HIGHMEM available. //高级内存为0MB
511MB LOWMEM available. //低级内存为511MB
found SMP MP-table at 000f5470
Memory for crash kernel (0x0 to 0x0) notwithin permissible range
disabling kdump //禁用kdump
Using x86 segment limits to approximate NX protection
On node 0 totalpages: 131056
DMA zone: 4096 pages, LIFO batch:0
Normal zone: 126960 pages, LIFO batch:31
DMI 2.3 present.
Using APIC driver default //默认使用APIC驱动
ACPI: RSDP (v000 IntelR ) @ 0x000f6f80
ACPI: RSDT (v001 IntelR AWRDACPI 0x42302e31 AWRD 0x00000000) @ 0x1fff3000
ACPI: FADT (v001 IntelR AWRDACPI 0x42302e31 AWRD 0x00000000) @ 0x1fff3040
ACPI: MADT (v001 IntelR AWRDACPI 0x42302e31 AWRD 0x00000000) @ 0x1fff7180
ACPI: DSDT (v001 INTELR AWRDACPI 0x00001000 MSFT 0x0100000d) @ 0x00000000

可以通过该日志文件来判断某些硬件设备在系统启动过程中是否被正确识别。例如，用户新添加了一个磁盘，如果该磁盘设备能被Linux系统正确识别，那么在dmesg日志文件中应该能够看到它的信息，如下所示。

Probing IDE interface ide0...
hda: Maxtor 6Y080L0, ATA DISK drive //原有的硬盘
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
Probing IDE interface ide1...
hdc: MAXTOR STM3160212A, ATA DISK drive //新添加的硬盘
ide1 at 0x170-0x177,0x376 on irq 15
hda: max request size: 128KiB
hda: Host Protected Area detected.
current capacity is 152729956 sectors (78197 MB)
native capacity is 160086528 sectors (81964 MB)
hda: Host Protected Area disabled.
hda: 160086528 sectors (81964 MB) w/2048KiB Cache, CHS=65535/16/63, UDMA(100)
hda: cache flushes supported
hda: hda1 hda2 < hda5 hda6 hda7 hda8 hda9 hda10 hda11 hda12 hda13 >
hdc: max request size: 512KiB
hdc: 312581808 sectors (160041 MB) w/2048KiB Cache, CHS=19457/255/63, UDMA(33) //硬盘大小为160041MB
hdc: cache flushes supported
hdc: hdc1[DM]
ide-floppy driver 0.99.newide

可以看到，新添加磁盘型号为MAXTOR STM3160212A，对应的设备文件名为/dev/hdc，大小为160041MB。