Air Carrier Captain reported being notified of a 'dirty socks' odor at the arrival gate . The Flight Attendant noticed the odor during approach until gate arrival. After conferring with Maintenance the number two Pack was MEL'ed for the return trip to the crew base where the aircraft was removed from service.

Narrative

I was first made aware of a dirty sock odor after the arrival of Aircraft X; ZZZ to ZZZZ.Upon landing and learning that we had to wait for a gate; we set up for a single engine taxi and shut down the number 2 engine. When we opened the flight deck door; the Flight Attendant 1 informed me that the Flight Attendant 3 smelled the odor on descent about 10 minutes out from landing. The cabin crew reported that the smell was still there at gate arrival but had dissipated a bit after engine 2 shutdown.I made a pass through the cabin and definitely smelled the odor lightly by mid cabin and more heavy in the rear of the aircraft. Since I didn't have advance notice of the odor; I didn't initiate any procedures. The odor spread throughout the aircraft as we sought to isolate the source with the mechanics.I called Dispatch via SATCOM and was patched through to maintenance who in turn had the local technicians attempt to isolate the smell. Following an engine run at the gate; it became apparent that pack 2 was the origination of the odor. Pack 2 was put on MEL and we operated the flight back to ZZZ on Pack 1 alone.The smell in the cabin was better on the return flight but the smell lingered thoughout the cabin and the flight deck all the way back to ZZZ where a Technician notified us of an odor history and took the aircraft out of service.The Flight Attendant 3 reported a burning sensation in his eyes on descent into ZZZZ associated with the odor. The cabin crew double masked once the smell was noticed but reported headaches with the smell. In helping the local mechanics analyze the problem; I too felt stomach pains and an associated headache due to the odor. None of the crew ever reported feeling sick enough to be ambulatory.