[CentOS] VM disk question

I have VMPlayer 12 running a CentOS 7 disk. Works fine.

However I wish to change the disk from UUID booting (fstab) to the old
style LABEL.
(so I can export it and use on another machine).

fdisk -l /dev/sda
Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0001c6d3

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048    20482047    10240000   83  Linux
/dev/sda2        20482048    22530047     1024000   82  Linux swap / Solaris
/dev/sda3        22530048    41943039     9706496   83  Linux

however when I run:
e2label /dev/sda1 /
e2label: Bad magic number in super-block while trying to open /dev/sda1
Couldn't find valid filesystem superblock.

Three questions:
1) Am I doing something wrong?
2) Is there a better way?
3) How do I support VM formats (VBox, VHD and VMWare) easily?

Thanks,
Jerry