When u have started activemq with console that appear the unknowhostexception, try the follow solutions.
java.net.UnknownHostException:
1, From your terminal, get your hostname, let’s say my hostname is linux-abc
# hostname
2, Edit the hosts files
# vi /etc/hosts
3, Add the hostname to the shortname
# IP-Address Full-Qualified-Hostname Short-Hostname
127.0.0.1 localhost linux-abc
4, Restart your ActiveMQ
ActiveMQ UnknownHostException: