默认CentOS7.x是无法直接升级到8.x任何版本的，为了解决CentOS7.x升级到8.x版本的问题，AlmaLinux推出了一个名为ELevate项目来帮助用户从7.x版本升级到8.x。

ELevate支持的操作系统有：AlmaLinux8、CentOS8、EuroLinux8、Oracle Linux8、Rocky Linux8。

项目官方网址：https://almalinux.org/elevate/

github开源地址：https://github.com/AlmaLinux/leapp-repository/tree/almalinux

请注意升级前一定要做好数据备份，避免某种原因导致升级失败！！！

CentOS7.x升级至RockyLinux8.x开始

1、更新当前CentOS7.x版本为最新

yum update

2、更新完成后重启

reboot

3、安装elevate库

yum install -y http://repo.almalinux.org/elevate/elevate-release-latest-el7.noarch.rpm

4、安装leapp包以及升级包

在文章开始介绍了ELevate支持5个7.x至8.x版本的系统升级，所以这里你要先确定要升级的8.x版本是哪一个，然后安装对应的升级包。

我这里是从7.x升级到rocky8.x，所以需要安装leapp-data-rocky包

yum install leapp-upgrade leapp-data-rocky -y

注：如果你是要升级到其他8.x版本则需要安装其他的包，总之想要升级到哪个版本就安装哪个

leapp-upgrade leapp-data-almalinux
leapp-upgrade leapp-data-centos
leapp-upgrade leapp-data-eurolinux
leapp-upgrade leapp-data-oraclelinux

5、升级前检查

执行升级前检查命令，Leapp会创建一个/var/log/leapp/leapp-report.txt文件，这个文件会包含可能出现的问题以及推荐的解决方案，在检查阶段，不会安装任何rpm包组。

注：如果你当前不允许root登录，则需要执行以下命令，放通root

sed -i 's/#PermitRootLogin yes/PermitRootLogin yes/g' /etc/ssh/sshd_config

执行升级前检查命令

leapp preupgrade

============================================================
                     UPGRADE INHIBITED                      
============================================================

Upgrade has been inhibited due to the following problems:
1. Inhibitor: A YUM/DNF repository defined multiple times
2. Inhibitor: Missing required answers in the answer file
Consult the pre-upgrade report for details and possible remediation.


============================================================
UPGRADE INHIBITED
==============================================================================



Debug output written to /var/log/leapp/leapp-preupgrade.log


============================================================
REPORT
===================================================================



A report has been generated at /var/log/leapp/leapp-report.json
A report has been generated at /var/log/leapp/leapp-report.txt

`============================================================
END OF REPORT`
`
============================================================`

解决检查出现的问题：

问题一：因为我这里安装了内网的yum源，和默认的源冲突了，所以我需要把冲突的源解决掉，如果你没有改动过yum源的话，一般也不会出现yum源的报错。

问题二：查看log

cat /var/log/leapp/leapp-report.txt

可以看到需要你执行这个命令

leapp answer --section remove_pam_pkcs11_module_check.confirm=True

问题解决完成后，再次执行升级前检查命令，确保检查升级通过

leapp preupgrade

看到以下内容，即表示检查通过

============================================================
                           REPORT                           
============================================================

A report has been generated at /var/log/leapp/leapp-report.json
A report has been generated at /var/log/leapp/leapp-report.txt

`============================================================
END OF REPORT`
`
============================================================`

6、开始升级

leapp upgrade

A reboot is required to continue. Please reboot your system.

Debug output written to /var/log/leapp/leapp-upgrade.log


============================================================
REPORT
===================================================================



A report has been generated at /var/log/leapp/leapp-report.json
A report has been generated at /var/log/leapp/leapp-report.txt

`============================================================
END OF REPORT                        `

7、根据上面提示，重启系统

reboot

重启后可以看到，系统还在进行升级操作

升级完成后，还会自动重启，二次自动重启完成后就是最新的Rocky8系统了

8、查看升级后的系统版本

cat /etc/os-release

NAME="Rocky Linux"
VERSION="8.7 (Green Obsidian)"
ID="rocky"
ID_LIKE="rhel centos fedora"
VERSION_ID="8.7"
PLATFORM_ID="platform:el8"
PRETTY_NAME="Rocky Linux 8.7 (Green Obsidian)"
ANSI_COLOR="0;32"
LOGO="fedora-logo-icon"
CPE_NAME="cpe:/o:rocky:rocky:8:GA"
HOME_URL="https://rockylinux.org/"
BUG_REPORT_URL="https://bugs.rockylinux.org/"
ROCKY_SUPPORT_PRODUCT="Rocky-Linux-8"
ROCKY_SUPPORT_PRODUCT_VERSION="8.7"
REDHAT_SUPPORT_PRODUCT="Rocky Linux"
REDHAT_SUPPORT_PRODUCT_VERSION="8.7"

至此升级完成