How the Russian squadron resupplied en route

Did the Russian squadron resupply in harbor or only at sea?

It resupplied largely in harbors rather than relying exclusively on replenishment at sea.

Most replenishment occurred in harbors. The Second Pacific Squadron did not sustain its whole global passage through open-ocean transfers. Harbor access remained central even when diplomatic restrictions made the voyage unusually difficult. A fleet's route depends on shore facilities and political permission as much as on the endurance of its ships.