First I ran this command:
geth --datadir “/home/blockchain/Downloads/privatechain/data” --networkid 99 --port 30303
And now I am trying to attach geth.ipc and start geth console but the connection is not happening.
$ geth attach /home/user/.ethereum/geth.ipc console
Fatal: Unable to attach to remote geth: dial unix /home/user/.ethereum/geth.ipc: connect: connection refused