For security reasons, manager and admin users are not activated in the standard configure files. In order to access the management or admin application, you need to create user credentials for these users. The easiest and quickest solution is to use the default user database in conf/tomcat-users.xml
In order to add users, edit the file
/etc/tomcat5/base/tomcat-users.xml
and add a role admin and manager. 

Sample file with admin user credentials 
admin/foo
and manager user credentials
manager/bar

<?xml version='1.0' encoding='utf-8'?>
<tomcat-users>
  <role rolename="tomcat"/>
  <role rolename="role1"/>
  <user username="tomcat" password="tomcat" roles="tomcat"/>
  <user username="role1" password="tomcat" roles="role1"/>
  <user username="both" password="tomcat" roles="tomcat,role1"/>
  
  <!-- new entries for manager and admin accounts -->
  <role rolename="admin"/>
  <role rolename="manager"/>
  <user username="admin" password="foo" roles="admin"/>
  <user username="manager" password="bar" roles="manager"/>
</tomcat-users>


