===== YUM Error performing checksum =====

<cli prompt='#'>
[root@openldap ~]# yum update
Loaded plugins: security
base                                                                                                                                                                     | 2.9 kB     00:00
base/primary_db                                                                                                                                                          | 1.9 MB     00:00
http://192.168.10.10:9999/CentOS/5.11/base/repodata/dc8d44cb1b8ee2488ce1570def00bcd7d6b6531276d084ebacf58ea0648363ae-primary.sqlite.bz2: [Errno -3] Error performing checksum
Trying other mirror.
base/primary_db                                                                                                                                                          | 1.9 MB     00:00
</cli>
Yum is not able to calculate the sha256 checksum correctly. Help him by installing the hash package from EPEL (http://dl.fedoraproject.org/pub/epel/5/x86_64/)
<cli prompt='#'>
[root@openldap ~]# rpm -Uhv python-hashlib-20081119-4.el5.x86_64.rpm
[root@openldap ~]# yum list |more
Loaded plugins: security
Installed Packages
Deployment_Guide-en-US.noarch            5.8-1.el5.centos              installed
GConf2.x86_64                            2.14.0-9.el5                  installed
MAKEDEV.x86_64                           3.23-1.2                      installed
NetworkManager.i386                      1:0.7.0-13.el5                installed
NetworkManager.x86_64                    1:0.7.0-13.el5                installed
NetworkManager-glib.i386                 1:0.7.0-13.el5                installed
NetworkManager-glib.x86_64               1:0.7.0-13.el5                installed
</cli>

===== YUM search a binary =====

find dig program:
<cli prompt='#'>
[root@openldap ~]# yum whatprovides dig
32:bind-utils-9.9.4-29.el7.ppc64le : Utilities for querying DNS name servers
Repo        : centos_base
Matched from:
Filename    : /usr/bin/dig
</cli>

===== YUM Error duplicate packages =====

Install package utilities
  # yum install yum-utils

Identify duplicate packages
  # package-cleanup --dupes

Cleanup duplicate packages
  # package-cleanup --cleandupes

Check problems
  # package-cleanup --problems

# yum check
# yum-complete-transaction

Another way to suppress duplicate, just remove the duplicate in the RPM database
  # rpm -e --justdb <package>
  
Remove old kernels
  # dnf remove --oldinstallonly