How do you refresh the MySQL configuration file without restarting?

You were so close! The kill -HUP method wasn’t working for me either.

You were calling:

select @@global.max_connections;

All you needed was to set instead of select:

set @@global.max_connections = 400;

See:

http://www.netadmintools.com/art573.html

How to update the max_connections setting in MySQL