Aria Operations for Logs is giving following error during the reboot: [FAILED] Failed to start Cloud-init

Products

• VCF Operations/Automation (formerly VMware Aria Suite)

Issue/Introduction

Aria Operations for Logs UI is inaccessible.

Rebooting the VM gives following error before it gets to the main screen:
[FAILED] Failed to start Cloud-init: Local Stage (pre-network).
[FAILED] Failed to start Operations for Logs Agent.
[FAILED] Failed to start Cloud-init: Network Stage.
[FAILED] Failed to start Cloud-init: Config Stage.
[FAILED] Failed to start Cloud-init: Final Stage.

Attempting to change the password with the command results in the following error in the Single user mode: 
passwd: Authentication token manipulation error
passwd: password unchanged

Running command: 'df -h' shows /dev/sda4 at 100% utilization

Environment

Aria Operations for Logs 8.18.x

Resolution

Follow kb: Large File Sizes of /var/log/messages and /var/mail/root Causing Root Partition to Fill Up in Aria Operations for Logs