Catalyzes the phosphorylation of N-acetyl-D-glucosamine (GlcNAc) derived from cell-wall degradation, yielding GlcNAc-6-P. ATP + N-acetyl-D-glucosamine = ADP + H(+) + N-acetyl-D-glucosamine 6-phosphate Cell wall biogenesis; peptidoglycan recycling. Belongs to the ROK (NagC/XylR) family. NagK subfamily.