How can phpMyAdmin be restarted after /etc/phpmyadmin/config.inc.php is changed?

No need to restart phpMyAdmin, changes in /etc/phpmyadmin/config.inc.php are automatically applied.

I was in a similar situation on Ubuntu 10.10 (phpmyadmin 3.3.7deb3build0.10.10.1) and even after editing /etc/phpmyadmin/config.inc.php I couldn't login (because of AllowNoPassword).

I had to cp /usr/share/phpmyadmin/config.sample.inc.php /usr/share/phpmyadmin/config.inc.php and then add the $cfg['Servers'][$i]['AllowNoPassword'] = TRUE; line to it.

It is strange, but it worked.

Try and open it using:

sudo gedit /etc/phpmyadmin/config.inc.php

Uncomment it and save, but keep it open - then try opening phpMyAdmin. It should work.