Is it technically possible to solo mine bitcoin using cpu without a pool? How? Ubuntu For development reasons I'd like to have a private "real" bitcoin mainnet network.
Bitcoin-core doesn't support mining any more.

I have set up a network of 2 nodes (using connect conf command).
CPUminer is designed (as far as I know) to connect to a mining pool server.

Any idea how to directly do cpu solo mining with bitcoin?

Thanks.
For development it's often helpful to start both nodes in regression test mode (regtest mode). The developer has his own private blockchain and can choose when to create a new block. You can use bitcoin-cli -regtest generate 1 to generate a new block.

For more information see Developer Examples - Regtest Mode.