Could not find or load main class org.apache.giraph.yarn.GiraphApplicationMaster
I resolved this issue with commands:
cp $GIRAPH_HOME/giraph-examples/target/giraph-examples-1.1.0-for-hadoop-2.6.0-jar-with-dependencies.jar $HADOOP_HOME/share/hadoop/yarn/lib/cp $GIRAPH_HOME/giraph-examples/target/ $HADOOP_HOME/share/hadoop/yarn/lib/
then, run your job