yum Multilib version problems
这两天在更新CentOS7系统时，出现了Multilib version problems错误，执行命令：
# yum update
出现了的错误信息：
....
---> Package libcap-ng.i686 0:0.7.5-4.el7 will be installed
---> Package libstdc++.i686 0:4.8.5-16.el7 will be installed
--> Finished Dependency Resolution
Error: Multilib version problems found. 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 glibc which is missing some
dependency that another package requires. Yum is trying to
solve this by installing an older version of glibc 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 glibc.otherarch ... this should give you an error
message showing the root cause of the problem.
2. You have multiple architectures of glibc 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 glibc 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: glibc-2.17-196.el7.i686 != glibc-2.17-157.el7_3.1.x86_64
Error: Protected multilib versions: pcre-8.32-17.el7.i686 != pcre-8.32-15.el7_2.1.x86_64
Error: Protected multilib versions: elfutils-libs-0.168-8.el7.i686 != elfutils-libs-0.166-2.el7.x86_64
......
解决过程如下：
//查询重复的软件包
# rpm -q systemd-libs
systemd-libs-219-30.el7.x86_64
systemd-libs-219-42.el7_4.1.x86_64
//删除旧版
# rpm -e systemd-libs-219-30.el7.x86_64
error: Failed dependencies:
systemd-libs = 219-30.el7 is needed by (installed) libgudev1-219-30.el7.x86_64
//仍然出现依赖问题，继续查询libgudev1的版本信息
# rpm -q libgudev1
libgudev1-219-30.el7.x86_64
//发现只有一个版本，升级试一下
# yum update libgudev1
......
Updated:
libgudev1.x86_64 0:219-42.el7_4.1
Complete!
# rpm -q libgudev1
libgudev1-219-42.el7_4.1.x86_64
//升级完成后，删除旧版本的systemd-libs
# rpm -e systemd-libs-219-30.el7.x86_64
# rpm -q systemd-libs
systemd-libs-219-42.el7_4.1.x86_64
最后查询发现只剩下最新版本的systemd-libs，其他重复版本包的解决，也是同样的过程。
核心的命令主要是：
rpm -q package-names
rpm -e package-full-version
