Linux内核替换的一种简单方法

前言

使用现有centos的镜像，在海光机器上出现了无法运行的情况，grub引导后就只剩下光标一直在闪，无任何字符输出。这种情况大概率是因为Linux的内核无法运行在海光的CPU上所导致的。

已得知Linux内核在4.20版本后支持海光CPU，而在之前的版本中，则需要为内核打专门的patch，并编译内核。考虑到目前centos的软件源中并没有提供4.20版本以上的内核，而在其余开发环境中已有现成的5.15.11版本内核，故决定手动替换。

具体步骤

想要替换内核至5.15.11版本，至少需要从其他环境中复制如下文件：

• /boot/vmlinuz-5.15.11-1.el7.x86_64
• /boot/initramfs-5.15.11-1.el7.x86_64.img
• /lib/modules/5.15.11-1.el7.x86_64/目录

随后更新grub配置，确认grub中包含新内核的引导：

grub2-mkconfig -o /boot/grub2/grub.cfg

如果initrd存在定制，那么还需要为新内核生成一个initrd：

dracut -v -f -N --kver 5.15.11-1.el7.x86_64

最后重启验证新内核是否能够正常运行。

附录

Linux对海光的支持

https://cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.20

commit fec98069fb72fb656304a3e52265e0c2fc9adf87
Merge: 04ce7fae3d4e 995d5f64b62f
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue Oct 23 16:16:40 2018 +0100

    Merge branch 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
    
    Pull x86 cpu updates from Ingo Molnar:
     "The main changes in this cycle were:
    
       - Add support for the "Dhyana" x86 CPUs by Hygon: these are licensed
         based on the AMD Zen architecture, and are built and sold in China,
         for domestic datacenter use. The code is pretty close to AMD
         support, mostly with a few quirks and enumeration differences. (Pu
         Wen)
    
       - Enable CPUID support on Cyrix 6x86/6x86L processors"
    
    * 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
      tools/cpupower: Add Hygon Dhyana support
      cpufreq: Add Hygon Dhyana support
      ACPI: Add Hygon Dhyana support
      x86/xen: Add Hygon Dhyana support to Xen
      x86/kvm: Add Hygon Dhyana support to KVM
      x86/mce: Add Hygon Dhyana support to the MCA infrastructure
      x86/bugs: Add Hygon Dhyana to the respective mitigation machinery
      x86/apic: Add Hygon Dhyana support
      x86/pci, x86/amd_nb: Add Hygon Dhyana support to PCI and northbridge
      x86/amd_nb: Check vendor in AMD-only functions
      x86/alternative: Init ideal_nops for Hygon Dhyana
      x86/events: Add Hygon Dhyana support to PMU infrastructure
      x86/smpboot: Do not use BSP INIT delay and MWAIT to idle on Dhyana
      x86/cpu/mtrr: Support TOP_MEM2 and get MTRR number
      x86/cpu: Get cache info and setup cache cpumap for Hygon Dhyana
      x86/cpu: Create Hygon Dhyana architecture support file
      x86/CPU: Change query logic so CPUID is enabled before testing
      x86/CPU: Use correct macros for Cyrix calls

内核rpm包中包含的文件

以内核版本4.18.0为例，首先使用rpm命令查询内核rpm包中包含有哪些文件，如下所示，rpm包中包含的文件有：

• 内核文件：/boot/vmlinuz-4.18.0-348.7.1.el8_5.x86_64
• initrd压缩包：/boot/initramfs-4.18.0-348.7.1.el8_5.x86_64.img
• 内核编译文件（一般用不到）：Module.symvers文件boot/symvers-4.18.0-348.7.1.el8_5.x86_64.gz、配置文件/boot/config-4.18.0-348.7.1.el8_5.x86_64、内核符号表/boot/System.map-4.18.0-348.7.1.el8_5.x86_64、内核完整性校验文件/boot/.vmlinuz-4.18.0-348.7.1.el8_5.x86_64.hmac等
• 动态库加载配置文件：/etc/ld.so.conf.d/kernel-4.18.0-348.7.1.el8_5.x86_64.conf
• 内核模块：/lib/modules/4.18.0-348.7.1.el8_5.x86_64/目录下的各种文件
• 文档、签名、许可证等杂项：/usr/share/目录下的文件

# rpm -ql kernel-core-4.18.0-348.7.1.el8_5.x86_64
/boot/.vmlinuz-4.18.0-348.7.1.el8_5.x86_64.hmac
/boot/System.map-4.18.0-348.7.1.el8_5.x86_64
/boot/config-4.18.0-348.7.1.el8_5.x86_64
/boot/initramfs-4.18.0-348.7.1.el8_5.x86_64.img
/boot/symvers-4.18.0-348.7.1.el8_5.x86_64.gz
/boot/vmlinuz-4.18.0-348.7.1.el8_5.x86_64
/etc/ld.so.conf.d/kernel-4.18.0-348.7.1.el8_5.x86_64.conf
/lib/modules
/lib/modules/4.18.0-348.7.1.el8_5.x86_64
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/.vmlinuz.hmac
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/System.map
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/bls.conf
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/build
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/config
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/kernel
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/kernel/arch
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/kernel/arch/x86
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/kernel/arch/x86/crypto
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/kernel/arch/x86/crypto/blowfish-x86_64.ko.xz
/lib/modules/4.18.0-348.7.1.el8_5.x86_64/kernel/arch/x86/crypto/camellia-aesni-avx-x86_64.ko.xz
...
/usr/share/doc/kernel-keys/4.18.0-348.7.1.el8_5.x86_64
/usr/share/doc/kernel-keys/4.18.0-348.7.1.el8_5.x86_64/kernel-signing-ca-20140212.cer
/usr/share/doc/kernel-keys/4.18.0-348.7.1.el8_5.x86_64/kernel-signing-ca-20200609.cer
/usr/share/doc/kernel-keys/4.18.0-348.7.1.el8_5.x86_64/kernel-signing-ca.cer
/usr/share/licenses/kernel-core
/usr/share/licenses/kernel-core/COPYING-4.18.0