which directory data should i remove , so it will start downloading blockchain again ?
/root/.bitcoin/blocks ?
/root/.bitcoin/chainstate
You only need to delete
/root/.bitcoin/blocksYou might want to delete
chainstate (which contain all UTXO) and
txindex (which contain all transaction index) folder as well since both of them will be recreated anyway and just in case if those two are corrupted as well.