。
I only know him by name.
Literal
Name [only-だけ] [with-で] [only-しか] him [object-を] know-not.
An unusual double-exclusive: だけで + しか... ない. Literally 'only by name, [and] only [that]... don't know.' The stacking emphasizes the narrowness — 'only, just by name, nothing more.' しか is always paired with a negative verb for 'nothing but / only.' Overkill emphatic phrasing for effect.