Hadoop authentication method is set to SIMPLE but a Kerberos principal is – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-1.1

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Briefly, this error occurs when the Hadoop authentication method is set to [SIMPLE], but a Kerberos principal is provided. This mismatch in configuration causes the error. To resolve this, you can either change the Hadoop authentication method to Kerberos if you intend to use Kerberos for authentication, or remove the Kerberos principal if you want to use the SIMPLE authentication method. Ensure that the authentication method matches the type of principal provided.

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This guide will help you check for common problems that cause the log ” Hadoop authentication method is set to [SIMPLE]; but a Kerberos principal is ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: repositories, plugins.

Log Context

Log “Hadoop authentication method is set to [SIMPLE]; but a Kerberos principal is” classname is HdfsRepository.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :

        // Check if the user added a principal to use; and that there is a keytab file provided
        String kerberosPrincipal = repositorySettings.get(CONF_SECURITY_PRINCIPAL);

        // Check to see if the authentication method is compatible
        if (kerberosPrincipal != null && authMethod.equals(AuthenticationMethod.SIMPLE)) {
            logger.warn("Hadoop authentication method is set to [SIMPLE]; but a Kerberos principal is " +
                "specified. Continuing with [KERBEROS] authentication.");
            SecurityUtil.setAuthenticationMethod(AuthenticationMethod.KERBEROS; hadoopConfiguration);
        } else if (kerberosPrincipal == null && authMethod.equals(AuthenticationMethod.KERBEROS)) {
            throw new RuntimeException("HDFS Repository does not support [KERBEROS] authentication without " +
                "a valid Kerberos principal and keytab. Please specify a principal in the repository settings with [" +


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