Case 1: Error occurring during VCN

VCN_Count Limit exceeded.

The following service limits were exceeded: vcn-count. Request a service limit increase from the service limits page in the console.

Root Cause: VCN Count Limit exceeded.

Solution1 : Either increase the service imit.

Solution2: Delete the unused or unwanted VCNs.(This method was adopted)

Deletion of Unused VCN

Deleted successfully. Now no VCN is available in that selected compartment.

Case 2: "Target is busy" error while Unmounting mounted volume

The "Target is busy" error occurs when you attempt to unmount a mounted volume or file system.

Root Cause: This happens because the operating system prevents unmounting volume that is still in use by a process or application. In our case,process id was attached to the mounted volume, which was preventing it from getting unmounted.

Solution: The process id needs to be deleted after confirmation from the application team. Once deleted, the mount volume can be unmounted.

Case 3: Root login failed post Boot volume attachment to New Instance

After attaching the Boot volume to the New Instance, was unable to login to Root user with password.

Root Cause: In /etc/ssh/sshd_config file, PasswordAuthentication parameter was set to No

Solution: In /etc/ssh/sshd_config file, set "PasswordAuthentication yes". After that, login to Root user with password is successful.