After creation, what I have to do with a coinbase transaction? I have create a coinbase transaction successfully with the command:

createrawtransaction '[{"txid":"0000000000000000000000000000000000000000000000000000000000000000","vout":0}]' '{"12Evb28oMpkP76HRS2CZ7VjNMD25B84VMv":12.5}'


what give a hex string for the transaction. But when I try signrawtransaction I got this error:

{
  "hex": "...",
  "complete": false,
  "errors": [
    {
      "txid": "0000000000000000000000000000000000000000000000000000000000000000",
      "vout": 0,
      "scriptSig": "",
      "sequence": ...,
      "error": "Input not found or already spent"
    }
  ]
}


with sendrawtransactions i got:

Missing inputs (code -25)


what I have to do with this transaction after create it?
A coinbase transaction is not one that is signed or broadcast to the network. Rather it should be the first transaction in the block that you are mining. Also, the first 4 bytes of the scriptSig must be the block's height (1 byte for pushdata 3 bytes for the height).