解决CentOS 7 上yum update时出现的Error: Multilib version problems found.

现象描述

CentOS 7.5 系统，sudo yum update，出现如下错误：

<strong>Error:  Multilib version problems found.</strong> This often means that the root cause is something else and multilib version checking is just pointing out that there is a problem. Eg.:
       
 1. You have an upgrade for audit-libs which is missing some dependency that another package requires. Yum is trying to solve this by installing an older version of audit-libs of the different architecture. If you exclude the bad architecture yum will tell you what the root cause is (which package requires what). You can try redoing the upgrade with --exclude audit-libs.otherarch ... this should give you an error message showing the root cause of the problem.
       
 2. You have multiple architectures of audit-libs installed, but yum can only see an upgrade for one of those architectures.
 If you don't want/need both architectures anymore then you can remove the one with the missing update and everything will work.
       
 3. You have duplicate versions of audit-libs installed already. You can use "yum check" to get yum show these errors. ...you can also use --setopt=protected_multilib=false to remove this checking, however this is almost never the correct thing to do as something else is very likely to go wrong (often causing much more problems).
       
 Protected multilib versions: -2.8.1-3.el7_5.1.i686 != audit-libs-2.8.1-3.el7.x86_64
Error: Protected multilib versions: systemd-libs-219-57.el7_5.1.i686 != systemd-libs-219-57.el7.x86_64

尝试单独更新相关软件包

单独更新audit-libs，失败

sudo yum update audit-libs

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.usc.edu
 * elrepo-kernel: repos.lax-noc.com
 * epel: mirrors.develooper.com
 * extras: mirrors.xtom.com
 * updates: mirror.hostduplex.com
 * webtatic: us-east.repo.webtatic.com
Resolving Dependencies
--> Running transaction check
---> Package audit-libs.i686 0:2.8.1-3.el7 will be updated
---> Package audit-libs.x86_64 0:2.8.1-3.el7 will be updated
--> Processing Dependency: audit-libs(x86-64) = 2.8.1-3.el7 for package: audit-libs-python-2.8.1-3.el7.x86_64
--> Processing Dependency: audit-libs(x86-64) = 2.8.1-3.el7 for package: audit-2.8.1-3.el7.x86_64
---> Package audit-libs.i686 0:2.8.1-3.el7_5.1 will be an update
---> Package audit-libs.x86_64 0:2.8.1-3.el7_5.1 will be an update
--> Running transaction check
---> Package audit.x86_64 0:2.8.1-3.el7 will be updated
---> Package audit.x86_64 0:2.8.1-3.el7_5.1 will be an update
---> Package audit-libs-python.x86_64 0:2.8.1-3.el7 will be updated
---> Package audit-libs-python.x86_64 0:2.8.1-3.el7_5.1 will be an update
--> Finished Dependency Resolution

Dependencies Resolved
=======================================================================================================================================================
 Package                                  Arch                          Version                                   Repository                      Size
=======================================================================================================================================================
Updating:
 audit-libs                               i686                          2.8.1-3.el7_5.1                           updates                        100 k
 audit-libs                               x86_64                        2.8.1-3.el7_5.1                           updates                         99 k
Updating for dependencies:
 audit                                    x86_64                        2.8.1-3.el7_5.1                           updates                        247 k
 audit-libs-python                        x86_64                        2.8.1-3.el7_5.1                           updates                         75 k

Transaction Summary
=======================================================================================================================================================
Upgrade  2 Packages (+2 Dependent packages)

Total size: 521 k
Is this ok [y/d/N]: y
Downloading packages:
Running transaction check
Running transaction test


Transaction check error:
  package audit-libs-2.8.1-3.el7_5.1.x86_64 is already installed

Error Summary
-------------

单独更新systemd-libs，失败

sudo yum update systemd-libs

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.usc.edu
 * elrepo-kernel: repos.lax-noc.com
 * epel: mirrors.develooper.com
 * extras: mirrors.xtom.com
 * updates: mirror.hostduplex.com
 * webtatic: us-east.repo.webtatic.com
Resolving Dependencies
--> Running transaction check
---> Package systemd-libs.i686 0:219-57.el7 will be updated
--> Processing Dependency: systemd-libs = 219-57.el7 for package: systemd-219-57.el7.x86_64
--> Processing Dependency: systemd-libs = 219-57.el7 for package: libgudev1-219-57.el7.x86_64
---> Package systemd-libs.x86_64 0:219-57.el7 will be updated
--> Processing Dependency: systemd-libs = 219-57.el7 for package: systemd-219-57.el7.x86_64
---> Package systemd-libs.i686 0:219-57.el7_5.1 will be an update
---> Package systemd-libs.x86_64 0:219-57.el7_5.1 will be an update
--> Running transaction check
---> Package libgudev1.x86_64 0:219-57.el7 will be updated
---> Package libgudev1.x86_64 0:219-57.el7_5.1 will be an update
---> Package systemd-libs.i686 0:219-57.el7 will be updated
--> Processing Dependency: systemd-libs = 219-57.el7 for package: systemd-219-57.el7.x86_64
---> Package systemd-libs.x86_64 0:219-57.el7 will be updated
--> Processing Dependency: systemd-libs = 219-57.el7 for package: systemd-219-57.el7.x86_64
--> Finished Dependency Resolution
Error: Package: systemd-219-57.el7.x86_64 (@base)
           Requires: systemd-libs = 219-57.el7
           Removing: systemd-libs-219-57.el7.i686 (@base)
               systemd-libs = 219-57.el7
           Updated By: systemd-libs-219-57.el7_5.1.i686 (updates)
               systemd-libs = 219-57.el7_5.1
 You could try using --skip-broken to work around the problem
** Found 18 pre-existing rpmdb problem(s), 'yum check' output follows:
....

解决办法

系统是64位的，我们在上一步发现了两个不符合x86_64构架的包全名：

audit-libs.i686 0:2.8.1-3.el7

systemd-libs-219-57.el7.i686

需要做的就是移除它们：

sudo yum remove audit-libs.i686 0:2.8.1-3.el7

sudo yum update