OCI: SSH Connection Fails After Upgrading from Oracle Linux 8 to Oracle Linux 9

Applies To:

Oracle Cloud Infrastructure

Oracle Linux OS

Symptoms

After upgrading from Oracle Linux 8 to Oracle Linux 9, the system was not reachable via SSH (PuTTY) due to a connection timeout.

Cause

· The NetworkManager package was not fully set up post-upgrade. Although the package was installed, NetworkManager remained masked, preventing it from managing network interfaces.

· The ens3 interface was down, and NM_CONTROLLED was not set to yes in the configuration file.

Solution

1. Unmask and Start NetworkManager:

Run the following commands to restore NetworkManager functionality:

# systemctl unmask NetworkManager
# systemctl start NetworkManager

2. Enable NetworkManager to Start on Boot:

# systemctl enable NetworkManager

3. Update Network Configuration