As of SERVER-85420 on master, starting mongod with the --fork flag on macOS is not allowed. However, the MMS Automation Agent does not yet support starting mongod on macOS without the --fork flag. Cloud engineers working on Backup and Automation are using Macs. Due to this combination, integrating features requiring a build of server from master is blocked.

Setting the MONGODB_CONFIG_OVERRIDE_NOFORK=1 env variable currently allows the server to still start with the --fork flag, but it disables the forking behavior. We need the forking behavior.

After discussion, starting with --fork will be allowed on Macs if the MONGODB_CONFIG_OVERRIDE_NOFORK=1 environment variable is set. It will generate a warning instead of the current error.