Sometimes during busy parts of the day, my site shows a 'Too Many Connections' error.

I know it's to do with the maximum default being 100, and that I need to change the 'max_connections' in the my.cnf file. I am on a dedicated Linux server.

How can I change the max_connections to a higher number?
When I type '/etc/my.cnf' in SSH, I get '/etc/my.cnf: Permission denied'