## 错误

Loaded plugins: fastestmirror
Resolving Dependencies
There are unfinished transactions remaining. You might consider running yum-complete-transaction, or "yum-complete-transaction --cleanup-only" and "yum history redo last", first to finish them. If those don't work you'll have to try removing/installing packages by hand (maybe package-cleanup can help).
The program yum-complete-transaction is found in the yum-utils package.
--> Running transaction check
---> Package nss-softokn-freebl.i686 0:3.44.0-5.el7 will be updated
---> Package nss-softokn-freebl.i686 0:3.44.0-8.el7_7 will be an update
--> 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 nss-softokn-freebl which is missing some
dependency that another package requires. Yum is trying to
solve this by installing an older version of nss-softokn-freebl 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 nss-softokn-freebl.otherarch ... this should give you an error
message showing the root cause of the problem.

2. You have multiple architectures of nss-softokn-freebl 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 nss-softokn-freebl 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: nss-softokn-freebl-3.44.0-8.el7_7.i686 != nss-softokn-freebl-3.44.0-5.el7.x86_64

## 解决办法

　　　　yum install yum-utils
yum-complete-transaction --cleanup-only
#清除可能存在的重复包
package-cleanup --dupes
#清除可能存在的损坏包
package-cleanup --problems
#清除重复包的老版本：
package-cleanup --cleandupes