"Greg is someone who has interested us for a long time," McInnes continued. "We scouted Nottingham Forest a number of times at the back end of last season and he really caught the eye.
"He's a good player who is only going to improve. Greg is a solid defender, determined and full of energy and pace.
"We had a number of options put to us in that position but good left-backs are hard to find and Greg was always the one we wanted. I believe we have secured the services of one of the best up-and-coming left backs
"It's a great financial deal for the club and we get an excellent player out of it on a long-term, secure contract."Cunningham has spent time away from the City of Manchester Stadium on loan in the past few seasons, impressing during spells at Leicester City and Nottingham Forest. In 2010, the Galway-born defender received his first senior call-up under Giovanni Trapattoni and made his debut in the May friendly against Algeria at the RDS.