# Troubleshooting SSH

When using SSH to connect and authenticate to GitHub, you may need to troubleshoot unexpected issues that may arise.

## Links

* [/using-ssh-over-the-https-port](/en/enterprise-server@3.21/using-ssh-over-the-https-port)

* [Recovering your SSH key passphrase](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/recovering-your-ssh-key-passphrase)

  If you've lost your SSH key passphrase, depending on the operating system you use, you may either recover it or you may need to generate a new SSH key passphrase.

* [/deleted-or-missing-ssh-keys](/en/enterprise-server@3.21/deleted-or-missing-ssh-keys)

* [/error-host-key-verification-failed](/en/enterprise-server@3.21/error-host-key-verification-failed)

* [Error: Permission denied (publickey)](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-permission-denied-publickey)

  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.

* [Error: Bad file number](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-bad-file-number)

  This error usually means you were unable to connect to the server. Often this is caused by firewalls and proxy servers.

* [Error: Key already in use](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-key-already-in-use)

  This error occurs when you try to add a key that's already been added to another account or repository.

* [Error: Permission to user/repo denied to other-user](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-permission-to-userrepo-denied-to-other-user)

  This error means the key you are pushing with is attached to an account which does not have access to the repository.

* [Error: Permission to user/repo denied to user/other-repo](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-permission-to-userrepo-denied-to-userother-repo)

  This error means the key you are pushing with is attached to another repository as a deploy key, and does not have access to the repository you are trying to push to.

* [Error: Agent admitted failure to sign](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-agent-admitted-failure-to-sign)

  In rare circumstances, connecting to GitHub via SSH on Linux produces the error "Agent admitted failure to sign using the key". Follow these steps to resolve the problem.

* [Error: ssh-add: illegal option -- apple-use-keychain](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-ssh-add-illegal-option----apple-use-keychain)

  This error means your version of ssh-add does not support macOS keychain integration, which allows you to store your passphrase in the keychain.

* [/error-ssl-certificate-problem-verify-that-the-ca-cert-is-ok](/en/enterprise-server@3.21/error-ssl-certificate-problem-verify-that-the-ca-cert-is-ok)

* [Error: Unknown key type](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-unknown-key-type)

  This error means that the SSH key type you used was unrecognized or is unsupported by your SSH client.

* [Error: We're doing an SSH key audit](/en/enterprise-server@3.21/authentication/troubleshooting-ssh/error-were-doing-an-ssh-key-audit)

  This error means the SSH key you're using to perform a Git operation is unverified.