Fix SSH Passwordless Login Issues on Linux

2 years ago

Olivia Parker

2 minutes

If you encounter issues with SSH keyless login on Linux, there are several common problems and solutions.

Check the SSH server configuration on the target host: make sure the SSH server is properly configured to allow public key authentication. You can edit the /etc/ssh/sshd_config file on the target host to ensure that the following configuration options are not commented out or set to yes:
Enable RSA authentication and public key authentication, and specify the location of the authorized keys file as .ssh/authorized_keys.
Then restart the SSH server by running “sudo systemctl restart sshd”.
Check the user directories and permissions on the target host: Verify if the permissions of the .ssh directory and authorized_keys file for users on the target host are correct. The .ssh directory should have permissions set to 700 and the authorized_keys file should have permissions set to 600. You can use the following commands to correct the permissions:
Change the permissions of the “~/.ssh” directory to 700 and the “~/.ssh/authorized_keys” file to 600.
Check the SSH key and configuration on your local host: make sure you have the correct SSH key pair on your local host, and that the private key has not been modified or damaged. You can use the following command to check and generate SSH key pairs:
Display the contents of the ~/.ssh directory, and then generate an RSA key with a bit size of 4096.
Check the SSH configuration of your local host: Make sure there are no conflicting configurations in the SSH configuration file of your local host (usually ~ /.ssh/config). If there are conflicting configurations, you can try temporarily renaming or deleting the file, then try SSH keyless login again.

If none of the above methods have resolved the issue, you may need to check the log files for the SSH server and client to get more detailed error information. On the target host, you can check the /var/log/auth.log file, while on the local host, you can check the /var/log/secure or /var/log/auth.log file (specific location may vary depending on the Linux distribution).