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Labs

Troubleshooting Authentication Issues

In this exercise, you will need to troubleshoot and resolve authentication issues with LDAP, Kerberos, and PAM. *This course is not approved or sponsored by Red Hat.*

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Lab platform
Lab Info
Level
Advanced
Last updated
Sep 18, 2025
Duration
2h 0m

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Table of Contents
  1. Challenge

    Troubleshoot and resolve Server1.

    Resolve login issues for testuser01

    Try to log in as testuser01:

    ssh testuser01@localhost
    

    View /var/log/secure:

    tail /var/log/secure
    

    Attempt to pull the LDAP user information for testuser01:

    getent passwd testuser01
    

    Perform an LDAP search:

    ldapsearch -x *
    

    View and modify /etc/openldap/ldap.conf:

    vim /etc/openldap/ldap.conf
    

    Change:

    URI ldap://ldap.example.com/
    

    To:

    URI ldap://auth.example.com/
    

    Perform an LDAP search:

    ldapsearch -x *
    

    Restart the LDAP naming services daemon:

    systemctl restart nslcd
    

    Attempt to pull the LDAP user information for testuser01:

    getent passwd testuser01
    

    View /etc/sysconfig/authconfig:

    cat /etc/sysconfig/authconfig
    

    Modify authconfig using the TUI interface:

    authconfig-tui
    

    Within authconfig-tui:

    • Verify Use LDAP is checked under User Information
    • Check Use Kerberos under Authentication
    • Modify the LDAP server to use auth.example.com
    • Use auth.example.com for the KDC and Admin Server for Kerberos

    Restart the LDAP naming services daemon:

    systemctl restart nslcd
    

    Pull the LDAP user information for testuser01:

    getent passwd testuser01
    

    Log in to the localhost as testuser01:

    ssh testuser01@localhost
    

    Obtain a Kerberos ticket

    kinit
    

    List cached Kerberos tickets and logout:

    klist && exit
    

    Resolve Samba issues for cloud_user

    Verify Samba is started and enabled:

    systemctl start smb && systemctl enable smb
    

    Attempt to list the shares using cloud_user:

    smbclient -U cloud_user -L localhost
    

    View the Samba log:

    tail /var/log/samba/log.smbd
    

    View the Samba PAM config:

    cat /etc/pam.d/samba
    

    Verify the Samba package:

    rpm -V samba
    

    Move the modified file to /root/samba.pam.old:

    mv /etc/pam.d/samba /root/samba.pam.old
    

    Reinstall Samba:

    yum reinstall -y samba
    

    List the shares using cloud_user:

    smbclient -U cloud_user -L localhost
    
  2. Challenge

    Troubleshoot and resolve Server2.

    Use authconfig-tui to verify and modify LDAP/Kerberos authentication:

    authconfig-tui
    
    • Verify Use LDAP is checked for both User Information and Authentication
    • Verify Use Kerberos is checked for Authentication
    • LDAP server should be auth.example.com
    • Kerberos KDC and Admin should be auth.example.com

    Perform an LDAP search:

    ldapsearch -x *
    

    Ping the LDAP server:

    ping auth.example.com
    

    Note the IP, view the contents of /etc/hosts:

    cat /etc/hosts
    

    Modify /etc/hosts so that auth.example.com points to 10.0.1.5:

    vim /etc/hosts
    

    Perform an LDAP search:

    ldapsearch -x *
    

    Restart the LDAP naming services daemon:

    systemctl restart nslcd
    

    Pull the LDAP user information for testuser01:

    getent passwd testuser01
    

    Log in as testuser01:

    ssh testuser01@localhost
    

    Obtain a Kerberos ticket:

    kinit
    

    List Kerberos ticket cache:

    klist
    
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