Resize Ubuntu /dev/sda1 partition in VirtualBox VMDK when /dev/sda is already larger

Solution 1:

You have to first resize the partition with the following steps:

1. sudo parted /dev/sda to enter the prompt "(parted)" as the superuser
2. resizepart 1 to resize the partition 1
3. -0 resizes it to the end of the disk. - indicates that it should count from the end of the disk, not the start. This makes -0 the last sector of the disk - which is suitable when you want to make it as big as possible. Step 4:
4. quit to exit parted

The file system meta information needs to indicate the size of disk, and resize2fs updates this. Thus, after expanding, run resize2fs /dev/sda1.

It's highly recommended to do this in either single user mode / recovery mode, or with the file system mounted in read only mode. You can mount it read only by mount -o remount,ro /dev/sda1.

Extending is possible to do with filesystem in RW-mode, but it increases chances of data loss. As this is a VM, and you can easily make a backup, doing it with the volume mounted RW may make sense.

Addendum: run commands as root for desired effect.