I see lots of answers to this error: Plugin installation was unsuccessful due to error "unknown export types injectDefaultVars in plugin shield"
The answer is always fix the versions. ES and Shield version must match ... in my case they do.
[root@ELKhost elasticsearch]# /opt/kibana/bin/kibana plugin --install kibana/shield/2.4.4
Attempting to transfer from https://download.elastic.co/kibana/shield/shield-2.4.4.tar.gz
Transferring 9726777 bytes....................
Extracting plugin archive
Optimizing and caching browser bundles...
Plugin installation was unsuccessful due to error "unknown export types injectDefaultVars in plugin shield"
[root@vhaeceelk elasticsearch]# /opt/kibana/bin/kibana --version
[root@vhaeceelk elasticsearch]# /usr/share/elasticsearch/bin/elasticsearch --version
Version: 2.4.4, Build: fcbb46d/2017-01-03T11:33:16Z, JVM: 1.8.0_144
Is it a JAVA problem?
[root@ELKhost elasticsearch]# java -version
openjdk version "1.8.0_144"
OpenJDK Runtime Environment (build 1.8.0_144-b01)
OpenJDK 64-Bit Server VM (build 25.144-b01, mixed mode)
Going to X-PACK is not an option. I know these are old versions, but I have to due to company requirements .