The issue of “SSH key not recognized receive packet type 51 in GitLab CE” is a common problem encountered by users when trying to authenticate with GitLab using SSH keys. This error typically occurs when the SSH key provided is not recognized by the GitLab server, often due to incorrect key format, permissions issues, or misconfiguration. When this happens, users are unable to push or pull code from GitLab repositories, which can disrupt workflows and productivity.
Understanding the root cause of this error and implementing the appropriate fixes is crucial for maintaining smooth and secure operations within GitLab environments.
The error ‘ssh key not recognized receive packet type 51 in GitLab CE’ can be caused by several issues:
Incorrect SSH Key Configuration: Ensure that the SSH key pair is correctly generated and that the public key is added to your GitLab profile. Verify that the key is correctly referenced in your SSH configuration file.
SSH Agent Issues: Sometimes, the SSH agent might not be properly managing the keys. Try manually registering your private SSH key using ssh-agent.
Compatibility Problems: Ensure that the SSH key format is compatible with GitLab.
For example, GitLab supports RSA, ECDSA, and ED25519 keys. If the key format is not supported, it can cause issues.
Key Length Issues: GitLab has a limit on the length of RSA keys. Ensure that your RSA key is not longer than 8192 bits.
You can check the key length using the command openssl rsa -in <your-key-file> -text -noout | grep "Key:".
Incorrect Permissions: Ensure that the permissions of your SSH key files are set correctly. The private key file should have 600 permissions, and the public key file should have 644 permissions.
Debugging Connection: Run ssh -Tv [email protected] to debug the connection. Replace example.com with your GitLab URL.
This can help identify where the connection is failing.
By addressing these issues, you can resolve the ‘ssh key not recognized receive packet type 51 in GitLab CE’ error.
Check SSH Key Pair: Ensure you have generated an SSH key pair correctly and added the public key to your GitLab profile.
ssh-keygen -t rsa -b 4096 -C "[email protected]" ssh-copy-id -i ~/.ssh/id_rsa.pub [email protected]
Expected Output: Your identification has been saved in /home/your_username/.ssh/id_rsa. Your public key has been saved in /home/your_username/.ssh/id_rsa.pub. The key fingerprint is:
Verify SSH Key in GitLab: Check if the public key is correctly added to your GitLab profile.
Log in to GitLab.
Go to Settings > SSH Keys.
Ensure your public key is listed there.
Check SSH Agent: Ensure your SSH key is added to the SSH agent.
eval "$(ssh-agent -s)" ssh-add ~/.ssh/id_rsa
Expected Output: Identity added: /home/your_username/.ssh/id_rsa ([email protected])
Test SSH Connection: Debug the SSH connection to GitLab.
ssh -Tv [email protected]
Expected Output: Hi there! You've successfully authenticated, but GitLab does not provide shell access.
Check OpenSSH Version: Ensure you are using OpenSSH version 8.2 or greater.
ssh -V
Expected Output: OpenSSH_8.2p1, OpenSSL 1.1.1g 21 Apr 2020
Check Key Type: Verify the key type is supported by GitLab.
ssh-keygen -y -f ~/.ssh/id_rsa
Expected Output: ssh-rsa [email protected]
Check Permissions: Ensure the permissions of your SSH key files are correct.
chmod 700 ~/.ssh chmod 600 ~/.ssh/id_rsa chmod 644 ~/.ssh/id_rsa.pub
Check GitLab Logs: Check GitLab logs for any errors related to SSH.
Access the GitLab server.
Check the logs located at /var/log/gitlab/gitlab-rails/production.log.
Update GitLab: Ensure GitLab is up to date.
sudo gitlab-ctl reconfigure sudo gitlab-ctl restart
Check Firewall Settings: Ensure there are no firewall rules blocking SSH traffic.
sudo ufw status sudo ufw allow ssh
Check SSH Configuration: Ensure the SSH configuration file is correctly set up.
sudo nano /etc/ssh/sshd_config
Ensure the following lines are correctly set:
PermitRootLogin no PasswordAuthentication no PubkeyAuthentication yes
Restart SSH Service: Restart the SSH service to apply changes.
sudo systemctl restart sshd
Check for Errors: If the issue persists, check for any specific error messages in the logs and search for solutions related to those errors.
By following these steps, you should be able to resolve the ‘ssh key not recognized receive packet type 51 in GitLab CE’ issue. If the problem persists, consider reaching out to GitLab support for further assistance.
To verify the SSH key configuration in GitLab CE and ensure it is correctly set up, follow these steps:
Check SSH Key in GitLab Settings:
Log in to your GitLab account.
Click on your profile picture and select Preferences.
Go to the SSH Keys section.
Verify that your SSH key is listed. If it is, check the fingerprint to ensure it matches your local key.
Test SSH Connection:
Open your terminal.
Run the following command to test the connection:
ssh -T [email protected]
If the connection is successful, you should see a message confirming that you are authenticated.
Update SSH Key (if needed):
If your SSH key is not listed or you need to update it, go back to the SSH Keys section in your GitLab settings.
Click on Add key.
Copy your public key from your local machine (usually found in ~/.ssh/id_rsa.pub or ~/.ssh/id_ed25519.pub).
Paste the key into the Key field in GitLab.
Add a descriptive title for the key.
Click Add key to save the changes.
Verify Key Addition:
Go back to the SSH Keys section in your GitLab settings.
Ensure the new key appears with the correct fingerprint.
Test Connection Again:
Run the ssh -T [email protected] command again to confirm the new key is working.
By following these steps, you can verify and update your SSH key configuration in GitLab CE to ensure it is correctly set up.
To address persistent ‘ssh key not recognized receive packet type 51 in GitLab CE’ issues, follow these advanced solutions:
Check Server Logs: Review the SSH daemon logs to identify any authentication issues. Use commands like journalctl -u ssh or sudo grep sshd /var/log/auth.log to access logs. Look for entries related to authentication failures and packet types.
Consult GitLab Documentation: Refer to the GitLab documentation on SSH troubleshooting.
Ensure that your SSH key is correctly generated and added to your GitLab profile. Verify that the key type is supported by your OpenSSH version.
Update OpenSSH: Ensure that your OpenSSH version is up to date. Some issues may be resolved by updating to a newer version that supports the required key types.
Use ssh-agent: Manually register your private SSH key using ssh-agent to ensure it is correctly loaded.
Check Permissions: Verify that the permissions of your SSH key files are set correctly.
The private key should have 600 permissions, and the public key should have 644 permissions.
Debug SSH Connection: Run ssh -Tv [email protected] to debug the connection. Replace example.com with your GitLab URL. This command provides verbose output that can help identify issues.
By following these steps, you can diagnose and resolve persistent SSH key issues in GitLab CE.
Follow these steps:
If you encounter persistent ‘ssh key not recognized receive packet type 51 in GitLab CE’ issues, try:
Correct SSH key configuration is crucial to avoid these issues and ensure smooth interactions with your GitLab repository.