If you see an error message with Ubuntu Server 13.04 on EC2 like the following when trying to run commands:
perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LANGUAGE = (unset), LC_ALL = (unset), LANG = "en_GB.UTF-8" are supported and installed on your system. perl: warning: Falling back to the standard locale ("C"). Error: The locale requested by the environment is invalid.
Then run the following and reboot (you might want to update the locale though):
sudo echo "" >> /etc/environment sudo echo "LC_ALL=\"en_GB.utf8\"" >> /etc/environment
Reboot and this should fix your issues.