There are no good marinas in Ceffalonia. In all ports you will have to rely on your own anchor to moor bows/stern to the quay, with the consequent risk that when other boats depart they may lift your anchor . . .

And this is normal throughout the Ionian with the exception of Gouvia (Corfu), Preveza (alongside in the 'marina'), Levkas town (big new marina), Vliho Bay (alongside).

My website describes the area (among others) in some detail.