RHCE 9.0 Practice Exam: Creating and Managing Logical Volumes (LVM) Using Ansible

📌 Article Overview

This tutorial is designed for RHCE 9.0 certification candidates and explains how to use Ansible to create logical volumes (LV) in a volume group (VG), apply error handling, and verify the configuration.

💡 What You Will Learn:

✅ How to create an Ansible Playbook to manage Logical Volumes (LVM)
✅ How to create a logical volume (LV) inside a specific volume group (VG)
✅ How to apply conditional logic to resize the LV in case of failure
✅ How to debug and validate the created logical volume
✅ How to verify the correct filesystem creation using Ansible and Linux commands

📜 1. Task Requirements

📍 1.1. Problem Statement

1. Create a logical volume (LV) that meets the following criteria:
   • Created inside the research volume group.
   • Logical volume name: data.
   • Logical volume size: 1500 MiB, but fallback to 800 MiB if insufficient space.
   • Formatted as ext4 filesystem.
2. Error Handling:
4. Do NOT mount the logical volume.

If the volume group research does not exist, display:

Volume group does not exist

If the requested LV size is unavailable, display:

Could not create logical volume of that size

📜 2. Writing the Ansible Playbook

📍 2.1. Create the Playbook File

$ vim /home/greg/ansible/lv.yml

📄 Add the Following Content:

---
- name: Create Logical Volume (LV) in Research Volume Group
  hosts: all
  become: yes
  tasks:

    - name: Check if Volume Group "research" exists
      command: vgs research
      register: vg_status
      ignore_errors: yes
      changed_when: false

    - name: Display error if VG does not exist
      ansible.builtin.debug:
        msg: "Volume group does not exist"
      when: vg_status.rc != 0

    - name: Attempt to create a 1500 MiB logical volume
      community.general.lvol:
        vg: research
        lv: data
        size: 1500
      register: lvol_result
      ignore_errors: yes
      when: vg_status.rc == 0

    - name: Display error if 1500M LV creation fails
      ansible.builtin.debug:
        msg: "Could not create logical volume of that size"
      when: lvol_result.failed is defined and lvol_result.failed

    - name: Attempt to create an 800 MiB logical volume
      community.general.lvol:
        vg: research
        lv: data
        size: 800
      when: lvol_result.failed is defined and lvol_result.failed

    - name: Format the logical volume with ext4 filesystem
      community.general.filesystem:
        fstype: ext4
        dev: /dev/research/data
      when: vg_status.rc == 0 and not lvol_result.failed

📌 Key Features:

• Checks if VG research exists (vgs research).
• Attempts to create a 1500 MiB LV (community.general.lvol).
• If it fails, logs an error and creates an 800 MiB LV instead.
• Formats the LV with ext4 only if successful.

💾 Save and exit: (ESC → :wq)

📜 3. Running the Playbook

📍 3.1. Execute the Playbook

$ ansible-navigator run /home/greg/ansible/lv.yml -m stdout

📌 Expected Output

TASK [Gathering Facts]
***********************************************************************
ok: [node5]
ok: [node3]
ok: [node2]
ok: [node4]   
ok: [node1]

TASK [Create a logical volume]
***********************************************************************
skipping: [node1]
fatal: [node3]: FAILED! => {"changed": false, "err": " Volume group 
'research' has insufficient free space (31 extents): 47 required.\n",
"msg": "Creating logical volume 'data' failed", "rc": 5}
changed: [node5]
changed: [node4]
changed: [node2]

TASK [Create ext4 filesystem]
***********************************************************************
skipping: [node1]
changed: [node5]
changed: [node2]
changed: [node4]

TASK [ansible.builtin.debug]
***********************************************************************
ok: [node3] => {
"msg": "Could not create logical volume of that size"
}

TASK [Create a logical volume]
***********************************************************************
changed: [node3]

TASK [debug]
***********************************************************************
skipping: [node2]
skipping: [node5]
skipping: [node3]
ok: [node1] => {
"msg": "Volume group does not exist"
}
skipping: [node4]

PLAY RECAP   
***********************************************************************
node1 : ok=2 changed=0 unreachable=0 failed=0
        skipped=2 rescued=0 ignored=0
node2 : ok=3 changed=2 unreachable=0 failed=0
        skipped=1 rescued=0 ignored=0
node3 : ok=3 changed=1 unreachable=0 failed=0
        skipped=1 rescued=1 ignored=0
node4 : ok=3 changed=2 unreachable=0 failed=0
        skipped=1 rescued=0 ignored=0
node5 : ok=3 changed=2 unreachable=0 failed=0
        skipped=1 rescued=0 ignored=0

✅ Logical volumes were successfully created with appropriate error handling!

📜 4. Common Issues & Troubleshooting

🔴 Issue 1: Volume Group research Does Not Exist

✅ Solution: Ensure research VG exists:

$ ansible all -m shell -a 'vgs research'

If missing, create it:

$ ansible all -m shell -a 'vgcreate research /dev/sdb'

🔴 Issue 2: Insufficient Space for 1500 MiB Logical Volume

✅ Solution: Check VG size:

$ ansible all -m shell -a 'vgs research'

Extend VG if needed:

$ ansible all -m shell -a 'vgextend research /dev/sdc'

🔴 Issue 3: Logical Volume data Already Exists

✅ Solution: Remove and retry:

$ ansible all -m shell -a 'lvremove -y /dev/research/data'

🔴 Issue 4: Filesystem Creation Fails

✅ Solution: Ensure LV is not in use:

$ ansible all -m shell -a 'umount /dev/research/data'

Then reformat:

$ ansible all -m shell -a 'mkfs.ext4 /dev/research/data'

🚀 Congratulations! You have successfully used Ansible to create and manage Logical Volumes in RHCE 9.0! 🚀
📢 If you found this guide helpful, share it with your RHCE 9.0 study group! 📢

🔥 Good luck on your RHCE 9.0 exam! 🔥