>>262701I did that several years ago. Concrete walls, so just two holes with wall plugs and hooks held it.
After some time I did some adjustments and new knots. Because of a shitty knot the rope snapped and I fell on the floor with a pretty loud HNGGGGGGGGGGGGGROOOARRR. Must have sounded hilarious to the old couple living downstairs.
But hey, there's no way a hammock can be tightened enough if it's attached to walls. Some kind of frame should be built for it. At least for a full night's sleep.
I live in the countryside now so not my problem any more.