SYS‐255 Lab 3 Linux - aljimenez28/champlain GitHub Wiki

Overview

In this lab I configured a RockyOS virtual machine (dhcp01) to join the internal LAN, created a privileged user, verified network connectivity, and explored key Linux administration commands. The goal was to integrate a Linux system into a mixed-OS enterprise network while troubleshooting firewall and DNS issues.

Key Steps and Commands

1. Networking Configuration

  • nmtui – Configure static IP, gateway, and DNS.

    sudo nmtui
    • IP: 10.0.5.3/24
    • Gateway: 10.0.5.2
    • DNS: 10.0.5.5
    • Search Domain: yourname.local
    • Hostname: dhcp01-yourname

  • Activate --> Deactivate --> Reactivate

  • nmcli connection up – Bring the connection up after editing.

  • ping google.com – Test outside connectivity.

2. Privileged User

  • Create a user with admin rights:

    sudo useradd -m -G wheel alejandra
sudo passwd alejandra
groups alejandra

3. Connectivity Tests

  • Ping internal and external hosts:

    ping google.com
ping ad01
ping fw01

4. DNS Records

  • Added A and PTR records for dhcp01 on ad01 (Windows DNS).

  • Verified with:

    ping dhcp01

5. Remote Access

  • From WKS01:

    ssh alejandra@dhcp01-yourname

6. File Navigation and Sudo

  • pwd – Present working directory.
  • cd .. – Move up one directory.
  • ls -l – Long listing.
  • man hier – View directory hierarchy documentation.
  • mkdir ~/sys255 && cd ~/sys255 – Create and enter a new directory.
  • sudo dnf install tree – Install a package with elevated privileges.
  • sudo -i – Start a root shell.
  • whoami – Show current user.

7. History and Hidden Files

  • history – Display command history.
  • ls -la – Show hidden files.
  • cat .bash_history – View saved commands.
  • history -c – Clear bash history.

8. Extra Commands Explored

  • uptime – Display system load and uptime.
  • df -h – Disk usage in human-readable format.
  • free -m – Memory usage in MB.

Problems Encountered and Solutions

1. Firewall Routing Misconfiguration (Primary Root Cause)

  • Issue: dhcp01 could not reach the gateway or internet, and internal communication failed.

  • Cause: Firewall routing rules were incorrect, which blocked network traffic between subnets.

  • Fix:

    1. Reset wks01 and ad01 to clean snapshots.
    2. Restarted the configuration process from Lab 01 to restore correct firewall routing.
    3. Once routing was fixed, dhcp01 and wks01 immediately gained network connectivity.

2. Active Directory and DNS Errors

  • Issue: Forgot to change the computer name on ad01 and initially misconfigured DNS.

  • Impact: wks01 could not reliably join the domain.

  • Fix:

    1. Disconnected wks01 from the domain.
    2. Demoted ad01 from domain controller.
    3. Removed the DNS role and reset the AD configuration.
    4. Corrected the computer name, reinstalled DNS, and re-promoted ad01 as a domain controller.
    5. Rejoined wks01 to the rebuilt domain.
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