Tomcat install in ubuntu: error "java.net.BindException: Permission denied :80"

catalina.out error:

Jan 7, 2012 12:52:59 AM org.apache.catalina.startup.Catalina start
SEVERE: Catalina.start: 
LifecycleException:  service.getName(): "Catalina";  Protocol handler start failed: java.net.BindException: Permission denied :80
 at org.apache.catalina.connector.Connector.start(Connector.java:1087)
 at org.apache.catalina.core.StandardService.start(StandardService.java:531)
 at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
 at org.apache.catalina.startup.Catalina.start(Catalina.java:593)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
 at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)

Solution

Edit /etc/default/tomcat6 and set last line equal to:

# If you run Tomcat on port numbers that are all higher than 1023, then you                                                                                                    
# do not need authbind.  It is used for binding Tomcat to lower port numbers.                                                                                                  
# NOTE: authbind works only with IPv4.  Do not enable it when using IPv6.                                                                                                      
# (yes/no, default: no)                                                                                                                                                        
AUTHBIND=yes

What is authbind?

$ apt-cache show authbind
 Allows non-root programs to bind() to low ports
 This package allows a package to be started as non-root but
 still bind to low ports, without any changes to the application.

References

http://thelowedown.wordpress.com/2010/08/17/tomcat-6-binding-to-a-privileged-port-on-debianubuntu/