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12-B.9: Authentication Issues

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    What Causes Authentication Issues?

    Depending on what sort of authentication is configured there can be several issues that can keep users from successfully logging in.

    Password Authentication

    If a user is attempting to use login strictly with a userid and password:

    • Make sure the user is using the correct username.
    • User password authentication could be broken for some reason - did someone mess up a system config file?
    • Attempt a password reset.
    • Check that password authentication is allowed by the server.

    Key Error

    If the user is seeing some sort of key error:

    • Make sure the authorized_keys file and the private key itself have the correct permissions and ownership.
    • Check that key-based authentication is allowed by the server.
    • Make sure the private key is readable by the SSH client. If the user is using PuTTY, make sure the SSH keys are properly configured for the session. If the user is using an OpenSSH client, be sure the private SSH key has the proper permissions.
    • Make sure the authorized_keys file contains the matching public key.
    • The private key may no longer supported on the SSH service.

    12-B.9: Authentication Issues is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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