Some useful yum commands

1) Clean the yum cache directory.
yum clean all

2) To list installed.
yum list installed

3) List all versions of packages available. Can also query if repository is just added.
yum --showduplicate list [package_name]
yum --showduplicate list firefox

4) Install the specific version.
yum install [package_name]-[version].[architecture]
yum install firefox-31.5.3-3.el7_1.x86_64
yum install cassandra-3.11.2-1

5) To uninstall a package
yum remove [package_name]

6) To list repos
yum repolist
yum repolist all (shows both enable/disabled)
um-config-manager --disable datastax

7) To display path
update-alternatives --display java

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