Looking for an alternative to ubimirror

[PJ]

Hi,

Can anyone please recommend a procedure to copy one UBI volume to another? 

I'd like to execute from the bash command line, if possible.

One upon a time I was able to use ubimirror, however that command appears to
have been removed from mtd-utils. 

- The source volume will be mounted R/O as it is the rootfs. 
- The destination volume will be unrestricted (unmounted).
- Both the source and destination volumes are in the same device.

I checked the FAQ, the archive, and Google but I came up empty, so thanks.

Paul