A "Permission denied" error means that the server rejected your connection. There could be several reasons why, and the most common examples are explained below.

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_5.6p1, OpenSSL 0.9.8r 8 Feb 2011
debug1: Reading configuration data /Users/you/.ssh/config
debug1: Reading configuration data /etc/ssh_config
debug1: Applying options for *
debug1: Connecting to hostname [192.30.252.131] port 22.

Note the IP address (the numbers within the [ ] brackets). The connection should be made to an IP address that belongs to your GitHub Enterprise instance, on port 22.

Always use the "git" user

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

ssh -T billy.anyteen@hostname
Permission denied (publickey).

Instead, 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

  1. Open the terminal.

  2. Verify that you have a private key generated and loaded into SSH. If you're using OpenSSH 6.7 or older:

    # start the ssh-agent in the background
    eval "$(ssh-agent -s)"
    Agent pid 59566
    ssh-add -l
    2048 a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/you/.ssh/id_rsa (RSA)
    

    If you're using OpenSSH 6.8 or newer:

    # start the ssh-agent in the background
    eval "$(ssh-agent -s)"
    Agent pid 59566
    ssh-add -l -E md5
    2048 MD5:a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/you/.ssh/id_rsa (RSA)
    

If you have GitHub for Windows installed, you can use it to clone repositories and not deal with SSH keys. It also comes with the Git Bash tool, which is the preferred way of running git commands on Windows.

  1. If you are using Git Bash, turn on ssh-agent:

    # start the ssh-agent in the background
    eval "$(ssh-agent -s)"
    Agent pid 59566
    

    If you are using another terminal prompt, such as msysgit, turn on ssh-agent:

    # start the ssh-agent in the background
    eval $(ssh-agent -s)
    Agent pid 59566
    
  2. Verify that you have a private key generated and loaded into SSH. If you're using OpenSSH 6.7 or older:

    ssh-add -l
    2048 a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/you/.ssh/id_rsa (RSA)
    

    If you're using OpenSSH 6.8 or newer:

    ssh-add -l -E md5
    2048 MD5:a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/you/.ssh/id_rsa (RSA)
    
  1. Open the terminal.

  2. Verify that you have a private key generated and loaded into SSH. If you're using OpenSSH 6.7 or older:

    # start the ssh-agent in the background
    eval "$(ssh-agent -s)"
    Agent pid 59566
    ssh-add -l
    2048 a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/you/.ssh/id_rsa (RSA)
    

    If you're using OpenSSH 6.8 or newer:

    # start the ssh-agent in the background
    eval "$(ssh-agent -s)"
    Agent pid 59566
    ssh-add -l -E md5
    2048 MD5:a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/you/.ssh/id_rsa (RSA)
    
  1. Open Terminal (for Mac and Linux users) or the command prompt (for Windows users).

  2. Verify that you have a private key generated and loaded into SSH. If you're using OpenSSH 6.7 or older:

    # start the ssh-agent in the background
    eval "$(ssh-agent -s)"
    Agent pid 59566
    ssh-add -l
    2048 a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/you/.ssh/id_rsa (RSA)
    

    If you're using OpenSSH 6.8 or newer:

# start the ssh-agent in the background
eval "$(ssh-agent -s)"
Agent pid 59566
ssh-add -l -E md5
2048 MD5:a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/you/.ssh/id_rsa (RSA)

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.

Tip: On most systems the default private keys (~/.ssh/id_rsa, ~/.ssh/id_dsa and ~/.ssh/identity) are automatically added to the SSH authentication agent. You shouldn't need to run ssh-add path/to/key unless you override the file name when you generate a key.

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 to establish a secure connection.

  1. Open Terminal.
  2. Start SSH agent in the background.

    eval "$(ssh-agent -s)"
    Agent pid 59566
    
  3. Find and take a note of your public key fingerprint. If you're using OpenSSH 6.7 or older:

    ssh-add -l
    2048 a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/USERNAME/.ssh/id_rsa (RSA)
    

    If you're using OpenSSH 6.8 or newer:

    ssh-add -l -E md5
    2048 MD5:a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/USERNAME/.ssh/id_rsa (RSA)
    
  4. In the top right corner of any page, click . Settings icon in the user bar

  5. In the user settings sidebar, click SSH keys. SSH keys

  6. Compare the list of SSH keys with the output from the ssh-add command. SSH key listing in GitHub Enterprise

  1. Open the command line.
  2. Start SSH agent in the background.

    ssh-agent -s
    Agent pid 59566
    
  3. Find and take a note of your public key fingerprint. If you're using OpenSSH 6.7 or older:

    ssh-add -l
    2048 a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/USERNAME/.ssh/id_rsa (RSA)
    

    If you're using OpenSSH 6.8 or newer:

    ssh-add -l -E md5
    2048 MD5:a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/USERNAME/.ssh/id_rsa (RSA)
    
  4. In the top right corner of any page, click . Settings icon in the user bar

  5. In the user settings sidebar, click SSH keys. SSH keys

  6. Compare the list of SSH keys with the output from the ssh-add command. SSH key listing in GitHub Enterprise

  1. Open Terminal.
  2. Start SSH agent in the background.

    eval "$(ssh-agent -s)"
    Agent pid 59566
    
  3. Find and take a note of your public key fingerprint. If you're using OpenSSH 6.7 or older:

    ssh-add -l
    2048 a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/USERNAME/.ssh/id_rsa (RSA)
    

    If you're using OpenSSH 6.8 or newer:

    ssh-add -l -E md5
    2048 MD5:a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/USERNAME/.ssh/id_rsa (RSA)
    
  4. In the top right corner of any page, click . Settings icon in the user bar

  5. In the user settings sidebar, click SSH keys. SSH keys

  6. Compare the list of SSH keys with the output from the ssh-add command. SSH key listing in GitHub Enterprise

  1. Open Terminal.
  2. Start SSH agent in the background.

    eval "$(ssh-agent -s)"
    Agent pid 59566
    
  3. Find and take a note of your public key fingerprint. If you're using OpenSSH 6.7 or older:

    ssh-add -l
    2048 a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/USERNAME/.ssh/id_rsa (RSA)
    

    If you're using OpenSSH 6.8 or newer:

    ssh-add -l -E md5
    2048 MD5:a0:dd:42:3c:5a:9d:e4:2a:21:52:4e:78:07:6e:c8:4d /Users/USERNAME/.ssh/id_rsa (RSA)
    
  4. In the top right corner of any page, click . Settings icon in the user bar

  5. In the user settings sidebar, click SSH keys. SSH keys

  6. Compare the list of SSH keys with the output from the ssh-add command. SSH key listing in GitHub Enterprise

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

Warning: If you see an SSH key you're not familiar with on GitHub Enterprise, delete it immediately and contact your GitHub Enterprise site administrator, for further help. An unidentified public key may indicate a possible security concern. For more information, see "Keeping your SSH keys safe."