A production GCE VM uses an ext4 persistent disk and is nearing capacity. How do you add space with minimal downtime?

Increasing the size of a persistent disk in Google Cloud Platform (GCP) is an online operation. After increasing the disk size in the Cloud Console, you must extend the filesystem to utilize the new space. For ext4 filesystems, the resize2fs command is used for this purpose, which can be run while the VM is running, minimizing downtime. Shutting down the VM is unnecessary and causes downtime. The fdisk command shows partition tables, not filesystem size, and doesn't extend the filesystem. Creating a new disk or restoring from a snapshot introduces more complexity and downtime than simply resizing the existing disk and filesystem.