Usually when working with USB thumb drives, memory cards and hard drives, the partitioning can be easily done just by plugging them to a Linux (or Windows) PC and using a partitioning application such as fdisk. However, with embedded devices it is sometimes more practical to write the partition table to a file instead of directly writing it to the memory device. This can be the case with embedded MMC (eMMC) memories which are soldered directly to the device and cannot be connected to a PC for partitioning.
When working with embedded systems, the software is only a part of the whole product or device. Usually there is also customized hardware involved, and some parts of the software are very low-level and hardware dependent. With embedded Linux most parts of the software can quite easily be covered by unit testing on a Linux host. Yet, there are always some parts which need to be tested with the actual physical hardware. Using the right tools this testing can also be automated.