su
/etc/init.d/mysql status

Or:
ps aux | grep mysql

Or:
mysqladmin -u root -p status
You'll be prompted for your MySQL pass, not root pass.
Example output if running:
Threads: 1  Questions: 165  Slow queries: 0  Opens: 251  Flush tables: 1  Open tables: 612

View is MySQL is running and on port 3306:
netstat -tanp |grep 3306

Or:
lsof -i :3306

Or if port has been changed you can:
netstat -vulntp |grep -i mysql

exit