Hi, there're ssh key files in my server that are named id_dsa and id_dsa.pub. I wonder about if they are necessary, DirectAdmin needs SSH to work or not. Can I delete them?
The are most likely default keys. You can delete them safely if you don't need SSH.
SSH is not required for DA to work. It's just that some things need to be done via SSH so I would not disable SSH.
But those 2 can be deleted as they can also be created again at any time if required.
Maybe better protect it.
There is a topic about making SSH more safe if you have a look around.