Where can I find `BUFFER_PUBKEY` to upgrade a program?

Question

Which public key should be used as a <BUFFER_PUBKEY> and where can I find it?

solana program upgrade
error: The following required arguments were not provided:
    <BUFFER_PUBKEY>
    <PROGRAM_ID>

<BUFFER_PUBKEY>    Intermediate buffer account with new program data Address is one of:
                         * a base58-encoded public key
                         * a path to a keypair file
                         * a hyphen; signals a JSON-encoded keypair on stdin
                         * the 'ASK' keyword; to recover a keypair via its seed phrase
                         * a hardware wallet keypair URL (i.e. usb://ledger)

Answer 1

Buffer public key can be found by running this command.

solana program show --buffers

If you are going to upgrade program that has already been deployed, please use this command. (Your command is out-dated, I think.)

solana program deploy ./target/deploy/program_name.so --program-id 111111111111111111111111 --upgrade-authority /home/pc/.config/solana/id.json