从CentOS 7.0升级到7.7版本

我平时都在VirtualBox上装虚拟机，方法是导入ova镜像文件，比如导入从网上下载的CentOS7-base.ova，该ova为CentOS 7.0版本，而现在最新版本为7.7，为此进入系统后第一件事就是系统升级：

# yum update

可是该命令居然异常退出了！

重新进入系统后检查：

# uname -r
3.10.-123.9..el7.x86_64

# cat /proc/version
Linux version 3.10.-123.9..el7.x86_64 (builder@kbuilder.dev.centos.org) (gcc version 4.8.  (Red Hat 4.8.-) (GCC) ) # SMP Tue Oct  :: UTC 

# cat /etc/redhat-release
CentOS Linux release 7.7. (Core)

可见Linux发行版本号已改为7.7，但核心仍然是旧版本，并且再次执行yum update命令失败，说明系统未升级成功。经常一段时间摸索找到两种从7.0升级到7.7的方法。

方法一：升级失败后手工解决错误并重新升级

yum update命令异常退出后重新登录系统，然后执行：

清理上次失败的命令

# yum-complete-transaction --cleanup-only

查看重复的包

# package-cleanup --dupes
kbd-misc-1.15.-.el7.noarch
kbd-misc-1.15.-.el7.noarch
nss-tools-3.44.-.el7_7.x86_64
nss-tools-3.16.-.el7_0.x86_64
...
gzip-1.5-.el7.x86_64
gzip-1.5-.el7.x86_64

该命令本应无输出，但由于上次yum update命令失败导致大量重复的新旧包。

删除重复的包

# package-cleanup --cleandupes
...
Complete!
Warning: Some duplicates were not removed because they are required by installed packages.
You can try --cleandupes with --removenewestdupes, or review them with --dupes and remove manually.

该命令虽然删除了很多重复包，但提示未完全清除。

尝试重新升级

# yum update
...
--> Finished Dependency Resolution
Error: Package: avahi-libs-0.6.-.el7.x86_64 (@anaconda)
           Requires: avahi = 0.6.-.el7
           Removing: avahi-0.6.-.el7.x86_64 (@anaconda)
               avahi = 0.6.-.el7
           Updated By: avahi-0.6.-.el7.x86_64 (base)
               avahi = 0.6.-.el7
Error: firewalld conflicts with :NetworkManager-0.9.9.1-.git20140326.4dba720.el7_0..x86_64
Error: avahi-libs conflicts with avahi-0.6.-.el7.x86_64
 You could try using --skip-broken to work around the problem
...

仍升级失败！

根据上面的错误信息删除旧包

# rpm -e avahi-libs-0.6.-.el7.x86_64
error: Failed dependencies:
        avahi-libs = 0.6.-.el7 is needed by (installed) avahi-0.6.-.el7.x86_64
        avahi-libs = 0.6.-.el7 is needed by (installed) avahi-autoipd-0.6.-.el7.x86_64

该命令失败，原因是存在依赖项。为此需同时删除依赖项：

# rpm -e avahi-libs-0.6.-.el7.x86_64 \
> avahi-0.6.-.el7.x86_64 \
> avahi-autoipd-0.6.-.el7.x86_64
error: Failed dependencies:
        avahi-autoipd is needed by (installed) NetworkManager-:0.9.9.1-.git20140326.4dba720.el7_0..x86_64

仍有其它级联依赖项，一并删除：

# rpm -e avahi-libs-0.6.-.el7.x86_64 \
> avahi-0.6.-.el7.x86_64 \
> avahi-autoipd-0.6.-.el7.x86_64 \
> NetworkManager-:0.9.9.1-.git20140326.4dba720.el7_0..x86_64
error: Failed dependencies:
        NetworkManager = :0.9.9.1-.git20140326.4dba720.el7_0. is needed by (installed) NetworkManager-tui-:0.9.9.1-.git20140326.4dba720.el7_0..x86_64

继续一并删除：

# rpm -e avahi-libs-0.6.-.el7.x86_64 \
> avahi-0.6.-.el7.x86_64 \
> avahi-autoipd-0.6.-.el7.x86_64 \
> NetworkManager-:0.9.9.1-.git20140326.4dba720.el7_0..x86_64 \
> NetworkManager-tui-:0.9.9.1-.git20140326.4dba720.el7_0..x86_64

成功！

继续尝试升级

# yum update
...
Replaced:
  grub2.x86_64 :2.02-0.2..el7.centos.

Complete!

成功！成功升级后请重启系统：

# reboot

再次查看并删除重复的包

# package-cleanup --dupes
...
kbd-misc-1.15.-.el7.noarch
kbd-misc-1.15.-.el7.noarch
libdb-5.3.-.el7.x86_64
libdb-5.3.-.el7_0..x86_64
...
libteam-1.27-.el7.x86_64
libteam-1.9-.el7.x86_64

仍有一些重复的包，删除之：

# package-cleanup --cleandupes
...
--> Finished Dependency Resolution
Error: Rpmdb checksum is invalid: pkg checksums: grub2-tools-:2.02-0.2..el7.centos..x86_64
 You could try using --skip-broken to work around the problem
...

不知何故居然报错了，但再次执行就成功了：

# package-cleanup --cleandupes
...
Removed:
  audit-libs.x86_64 :2.3.-.el7                         bind-license.noarch :9.9.-.el7               device-mapper.x86_64 :1.02.-.el7
  device-mapper-event-libs.x86_64 :1.02.-.el7        device-mapper-libs.x86_64 :1.02.-.el7        dracut.x86_64 :-.el7
  e2fsprogs-libs.x86_64 :1.42.-.el7                    kbd-misc.noarch :1.15.-.el7                   libcom_err.x86_64 :1.42.-.el7
  libcurl.x86_64 :7.29.-.el7                          libdb.x86_64 :5.3.-.el7_0.                  libss.x86_64 :1.42.-.el7
  libteam.x86_64 :1.9-.el7                             systemd.x86_64 :-.el7_0.                   systemd-libs.x86_64 :-.el7_0.

Complete!

再检查一下是否有重复的包：

# package-cleanup --dupes

没有重复的包了。

重启系统并再次检查新版本号

# reboot

# uname -r
3.10.-1062.18..el7.x86_64

# cat /proc/version
Linux version 3.10.0-1062.18.1.el7.x86_64 (mockbuild@kbuilder.bsys.centos.org) (gcc version 4.8.5 20150623 (Red Hat 4.8.5-39) (GCC) ) #1 SMP Tue Mar 17 23:49:17 UTC 2020

# cat /etc/redhat-release
CentOS Linux release 7.7.1908 (Core)

完全正确！至此升级成功！

方法二：从7.0到7.5再到7.7版本

如果你已执行了yum update命令并且失败则只能用上面的方法一解决，本方法适用于新装系统。

从7.0升级到7.5版本

yum update命令默认升级到最新版，但我们可修改配置文件让其升级到指定的版本。

检查是否有更新

# yum list centos-release
...
Installed Packages
centos-release.x86_64                                                   7-0.1406.el7.centos.2.5                                                   @updates
Available Packages
centos-release.x86_64                                                   7-7.1908.0.el7.centos                                                     base

该命令显示当前版本是7.0，可升级到7.7版本（但我们知道升级会报错）。

修改CentOS-Base.repo文件，指向7.5版本库

把CentOS-Base.repo文件里的mirrorlist注释掉，并增加相应的baseurl，其它不变，如下：

# cat /etc/yum.repos.d/CentOS-Base.repo
...
[base]
...
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
baseurl=http://vault.centos.org/7.5.1804/os/$basearch/
...
[updates]
...
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
baseurl=http://vault.centos.org/7.5.1804/updates/$basearch/
...
[extras]
...
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
baseurl=http://vault.centos.org/7.5.1804/extras/$basearch/
...
[centosplus]
...
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus&infra=$infra
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
baseurl=http://vault.centos.org/7.5.1804/centosplus/$basearch/
...

清空缓存

修改配置文件后要清理一下缓存：

# yum clean all

再次检查更新

# yum list centos-release
Installed Packages
centos-release.x86_64                                                   -0.1406.el7.centos.2.5                                                   @updates
Available Packages
centos-release.x86_64                                                   -5.1804..el7.centos                                                     updates

可见如果升级则将升级到7.5版本。

升级到7.5版本

# yum update

升级成功后请reboot重启系统。

从7.5升级到7.7版本

把上面的CentOS-Base.repo文件还原、清空缓存、然后执行yum update即可。