Cannot delete old directories on Ubuntu 10.04 during installation

I think were doing rm <directory name> instead of rm -rf <directory name>

root@ubuntu1004-64:~# dpkg -i membase-server-enterprise_x86_64.deb
Selecting previously deselected package membase-server.
(Reading database ... 57597 files and directories currently installed.)
Unpacking membase-server (from membase-server-enterprise_x86_64.deb) ...
dpkg: warning: unable to delete old directory '/var/opt/membase/1.6.5/data': Directory not empty
dpkg: warning: unable to delete old directory '/var/opt/membase/1.6.5/logs': Directory not empty
dpkg: warning: unable to delete old directory '/var/opt/membase/1.6.5/mnesia': Directory not empty
dpkg: warning: unable to delete old directory '/var/opt/membase/1.6.5': Directory not empty
dpkg: warning: unable to delete old directory '/var/opt/membase': Directory not empty
dpkg: warning: unable to delete old directory '/var/opt': Directory not empty
Setting up membase-server (1.7.0r) ...

You have successfully installed Membase Server.
Please browse to http://ubuntu1004-64:8091/ to configure your server.
Please refer to http://couchbase.com for additional resources.

Please note that you have to update your firewall configuration to
allow connections to the following ports: 11211, 11210, 4369, 8091
and from 21100 to 21199.

By using this software you agree to the End User License Agreement.
See /opt/membase/LICENSE.txt.

• Started Membase server