HBase over rides the value of HBASE_OPTS (if any) set by client

Currently HBase will over ride the value of HBASE_OPTS (if any) set by user

export HBASE_OPTS="-XX:+UseConcMarkSweepGC" 

See hbase-env.sh

But, a user may have the following set in his environment:

HBASE_OPTS="-Xmn512m"

While starting the processes, HBase will internally over-ride the existing HBASE_OPTS value with the one set in hbase-env.sh

Instead of over-riding we can have the following in hbase-env.sh:

export HBASE_OPTS="$HBASE_OPTS -XX:+UseConcMarkSweepGC"