Backing up Device FW

I have a OpenWRT device that I'm wanting to backup the partitions to see if I can make any customization or enhancements.

I followed, however, I have two partitions that seem to not want to let me copy data from them.

Backing up mtd14 (log_data)
dd: can't open '/dev/mtd14ro': Resource busy

Backing up mtd16 (rootfs_data)
dd: can't open '/dev/mtd16ro': Resource busy

Not too worried about mtd14, but I'm assuming mtd16 is where the fun items are. What would be the best way to copy this out?

You can either extract it in uBoot, if your uboot has that function, or boot from an initramfs image and try from there.