虽然 Rocky Linux 专门写了一篇文档介绍如何从 CentOS 8 迁移过来，但实际迁移还是遇到了问题，这里简单记一下。

Error: 
 Problem 1: cannot install both ibus-libs-1.5.19-14.el8_5.x86_64 and ibus-libs-1.5.19-12.el8.x86_64
  - package ibus-devel-1.5.19-12.el8.x86_64 requires ibus-libs(x86-64) = 1.5.19-12.el8, but none of the providers can be installed
  - cannot install the best update candidate for package ibus-libs-1.5.19-12.el8.x86_64
  - problem with installed package ibus-devel-1.5.19-12.el8.x86_64
 Problem 2: cannot install both marisa-0.2.4-36.el8.x86_64 and marisa-0.2.4-4.el7.x86_64
  - package marisa-devel-0.2.4-4.el7.x86_64 requires marisa(x86-64) = 0.2.4-4.el7, but none of the providers can be installed
  - cannot install the best update candidate for package marisa-0.2.4-4.el7.x86_64
  - problem with installed package marisa-devel-0.2.4-4.el7.x86_64
(try to add '--allowerasing' to command line to replace conflicting packages or '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

第一个问题是升级 ibus-devel 失败，这是因为 ibus-devel 在 PowerTools 的仓库中，默认可能没有使能这个仓库，我们可以手动使能安装或升级：sudo dnf --enablerepo=powertools install ibus-devel。

第二个问题是 CentOS 8 上有最新的 marisa-0.2.4-36.el8.x86_64，但是只有marisa-devel-0.2.4-4.el7.x86_64, 这个有点奇怪，不知道为什么两个版本没有同步升级，marisa-devel 一般是用于开发，我们可能暂时用不到，可以先尝试卸载它完成升级：sudo dnf remove marisa-devel。

Syncing packages

Last metadata expiration check: 0:00:13 ago on Tue Mar  8 12:23:04 2022.

Error: 
 Problem: package kyotocabinet-1.2.77-1.el7.x86_64 requires kyotocabinet-libs(x86-64) = 1.2.77-1.el7, but none of the providers can be installed
  - kyotocabinet-libs-1.2.77-1.el7.x86_64 does not belong to a distupgrade repository
  - problem with installed package kyotocabinet-1.2.77-1.el7.x86_64
(try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

Error during distro-sync.

An error occurred while we were attempting to convert your system to Rocky Linux. Your system may be unstable. Script will now exit to prevent possible damage.

第三个问题是 kyotocabinet 的版本问题导致 distro-sync 失败。我查询了一下系统中安装的 kyotocabinet 版本又确实是 1.2.77-1.el7，也可以查询到迁移成功了：

$ hostnamectl 
   Static hostname: centos.tenneshop.com
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 2af6da6bd3624e0988bd30e22574b645
           Boot ID: 6edac64aba294e1e9f3b7cfdb7b6970c
    Virtualization: oracle
  Operating System: Rocky Linux 8.5 (Green Obsidian)
       CPE OS Name: cpe:/o:rocky:rocky:8:GA
            Kernel: Linux 4.18.0-240.15.1.el8_3.x86_64
      Architecture: x86-64

通过 Syncing packages 搜索 migrate2rocky 脚本，这已经是最后三步了，于是尝试手动完成剩下的工作。 先 dnf --allowerasing distro-sync，然后查看会删除哪些软件，我这里是会删除 kyotocabinet，根据情况确认是否接受删除软件同步。

最后的 Disable Stream repos 和移除 subscription-manage，因为是 CentOS 8, 所以并不需要。

重启之后又遇到新的问题：

vboxclient the virtualbox kernel service is not running. exiting

查看 /var/log/vboxadd-setup.log，

/tmp/vbox.0/r0drv/linux/alloc-r0drv-linux.c:204:14: error: implicit declaration of function ‘map_vm_area’; did you mean ‘get_vm_area’? [-Werror=implicit-function-declaration]
         if (!map_vm_area(pVmArea, PAGE_KERNEL_EXEC,
              ^~~~~~~~~~~
              get_vm_area
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:316: /tmp/vbox.0/combined-os-specific.o] Error 1
make[1]: *** [Makefile:1571: _module_/tmp/vbox.0] Error 2
make: *** [/tmp/vbox.0/Makefile-footer.gmk:117: vboxguest] Error 2

经过一番搜索，我意识到可能是 VBoxGuestAdditions.iso 的版本不对，因为之前确实有提示类似 unable to insert the virtual optical disk /usr/share/virtualbox/vboxguestadditions.iso 的错误，原因是我没有把之前版本的 VBoxGuestAdditions.iso 从虚拟光驱中弹出，于是先弹出再插入新版本，果然新版本成功安装。

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