I rarely used SSH to connect to the git repository before, but for a recent project, if I want to use webhook to try automatic deployment, I need to connect to git through SSH on the vps and perform the pull operation.
According to my understanding, after generating an ssh key pair, the private key is placed under .ssh/id_xxx of vps, and the public key can be uploaded through coding.net.
But I found that there are two types of ssh public keys in coding.net. According to the help page, one is to authenticate users, and the other is to deploy public keys to ensure read-only permissions. These two public keys are not universal yet. So the question is, do I need to generate two ssh keys on the vps and add them to the account public key and deployment public key in coding.net? In the same way, if there are two private keys locally and coding.net uploads an account public key and a deployment public key, which one will coding.net use?
Also, although one deployment public key can be used for multiple projects, I found that after the public key is uploaded successfully, the content cannot be seen. In this way, if the vps needs to deploy new projects after a while, the old deployment If the public key is not saved, do I need to get a new key?
In addition, after generating the ssh key, is the ssh-add operation still needed?
Additionally, the account public key and the deployment public key cannot be used interchangeably: 
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You don’t need a deployment key. The deployment key is for deployment and is not necessary if your users are all on the machine.
I don’t know why coding.net can’t see the public key. Both GitHub and BitBucket public keys are publicly visible. In addition, the public key can be generated from the private key. But the public key and the private key stay together. Why would you forget one of them?
I never ssh-add unless I need to use ssh-agent.
I feel like you rarely use ssh.