My cedar deck creaks when you walk across it. Any remedy?

Usually - it's deck screws that need tightening but I can't tell from the picture if yours are exposed or not. Do you have access to the fasteners?

Glue and screw. Locate the area of the squeak. If, possible, go underneath and put some construction adhesive in between the joists and the deck boards then from the top drive a few screws down through the same area. Alternatively, you can pull up the board or two from the squeak area, apply the glue to the joist and then screw the deck board back down. If the deck was installed with nails instead of screws, then the nails work their way up and squeak as they go. Replace nails with screws

The boards usually expand in the summer, and that seems to help. I've heard to put talc powder between the boards. Google it, " how to stop squeekie deck boards". Good Luck !