Error: Permission denied (publickey)

Should the sudo command be used with Git?

You should not be using the sudo command with Git. If you have a very good reason you must use sudo, then ensure you are using it with every command (it's probably just better to use su to get a shell as root at that point). If you generate SSH keys without sudo and then try to use a command like sudo git push, you won't be using the same keys that you generated.

Check that you are connecting to the correct server

Typing is hard, we all know it. Pay attention to what you type; you won't be able to connect to "githib.com" or "guthub.com". In some cases, a corporate network may cause issues resolving the DNS record as well.

To make sure you are connecting to the right domain, you can enter the following command:

$ ssh -vT git@hostname
> OpenSSH_8.1p1, LibreSSL 2.7.3
> debug1: Reading configuration data /Users/you/.ssh/config
> debug1: Reading configuration data /etc/ssh/ssh_config
> debug1: /etc/ssh/ssh_config line 47: Applying options for *
> debug1: Connecting to hostname port 22.

The connection should be made on port 22.

Always use the "git" user

All connections, including those for remote URLs, must be made as the "git" user. If you try to connect with your GitHub Enterprise Server username, it will fail:

$ ssh -T GITHUB-USERNAME@hostname
> Permission denied (publickey).

If your connection failed and you're using a remote URL with your GitHub Enterprise Server username, you can change the remote URL to use the "git" user.

You should verify your connection by typing:

$ ssh -T git@hostname
> Hi username! You've successfully authenticated...

Make sure you have a key that is being used

The ssh-add command should print out a long string of numbers and letters. If it does not print anything, you will need to generate a new SSH key and associate it with GitHub Enterprise Server.

Getting more details

You can also check that the key is being used by trying to connect to git@[hostname]:

$ ssh -vT git@hostname
> ...
> debug1: identity file /Users/you/.ssh/id_rsa type -1
> debug1: identity file /Users/you/.ssh/id_rsa-cert type -1
> debug1: identity file /Users/you/.ssh/id_dsa type -1
> debug1: identity file /Users/you/.ssh/id_dsa-cert type -1
> ...
> debug1: Authentications that can continue: publickey
> debug1: Next authentication method: publickey
> debug1: Trying private key: /Users/you/.ssh/id_rsa
> debug1: Trying private key: /Users/you/.ssh/id_dsa
> debug1: No more authentication methods to try.
> Permission denied (publickey).

In that example, we did not have any keys for SSH to use. The "-1" at the end of the "identity file" lines means SSH couldn't find a file to use. Later on, the "Trying private key" lines also indicate that no file was found. If a file existed, those lines would be "1" and "Offering public key", respectively:

$ ssh -vT git@hostname
> ...
> debug1: identity file /Users/you/.ssh/id_rsa type 1
> ...
> debug1: Authentications that can continue: publickey
> debug1: Next authentication method: publickey
> debug1: Offering RSA public key: /Users/you/.ssh/id_rsa

Verify the public key is attached to your account

You must provide your public key to GitHub Enterprise Server to establish a secure connection.

If you don't see your public key in GitHub Enterprise Server, you'll need to add your SSH key to GitHub Enterprise Server to associate it with your computer.