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VNC Login Error (Module is Unknown)

Last updated: 2022-04-06 20:30:25

    Error Description

    I entered the correct password, but still could not log in to the CVM using VNC. The message “Module is unknown” appears.

    Possible Reasons

    This issue may be caused by the /etc/pam.d/system-auth configuration in /etc/pam.d/login file.

    If the path of the pam_limits.so module is not configured correctly in the system-auth configuration file, the login fails.


    The pam_limits.so module limits the system resource usage of a user during the session. If the module path is not configured correctly according to the actual operating system, the login authentication fails.


    1. Perform the troubleshooting procedure to locate the pam_limits.so path configuration in the system-auth file.
    2. Correct the pam_limits.so module path.

    Troubleshooting Procedure

    1. Try to log in to Linux CVM via SSH key.
    1. Run the following command to view logs.
      vim /var/log/secure

    This file records the security information, mostly CVM login logs. You can check the error logs of /lib/security/pam_limits.so as shown below.

    3. Run the following commands in sequence to enter /etc/pam.d directory and search for /lib/security/pam_limits.so.

    cd /etc/pam.d
    find . | xargs grep -ri "/lib/security/pam_limits.so" -l

    If the result similar to the following figure is returned, /lib/security/pam_limits.so is configured in the system-auth file.

    4. Access the system-auth file to correct the pam_limits.so module path.
    For example, you can use the absolute path /lib64/security/pam_limits.so or a relative path pam_limits.so in a 64-bit operating system.

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