If a baker becomes inactive due to any inactivity or not baking for long time, how can i reactivate the baker? On tzscan.io the status is showing as inactive right now.
If a delegate doesn’t show any sign of activity for preserved_cycles it is marked inactive and its rights are removed. This mechanism is important to remove inactive delegates and reallocate their rights to the active ones so that the network is always working smoothly. Normally even a baker with one single roll should perform enough operations during 5 cycles to remain active. If for some reason you delegate is marked inactive you can reactivate it simply by re-registering again like below.
tezos-client register key "bob" as delegate