The blocksize (“bs=…”) is unimportant. This just provides higher performance and less time in most cases. Actual result will be the same with or without this.
I don’t have a Nano with eMMC, but if it is like flashing with the other Jetsons (and it probably is), then you could make a dd copy of the rootfs (or a clone using the flash.sh tool), then flashing the new Nano with the same release of L4T/JetPack/SDK manager, but substituting the clone for the sample root filesystem, should do what you want.
That sounds a bit complicated, but here is some information on what a clone and flash does (just to emphasize, I haven’t worked on the Nano with eMMC, but other than a few details this should be exactly the same as doing this on Xavier or TX2 or any of the other Jetsons)…
Of the many non-rootfs partitions, flashing will produce these. The actual root filesystem (rootfs) is the operating system. Flash software normally takes a purely Ubuntu sample rootfs, applies some binary drivers on top of this, and then flashes both the non-rootfs partitions and the rootfs. One can modify the sample rootfs prior to flash, and other than some boot related edits the content will be 100% copied to the actual eMMC of the Jetson. Instead of using the sample Ubuntu distribution you can use an already existing image (such as a clone). The release which produced the system being cloned must match the system being written.
When a partition is read by “dd” and then saved somewhere this is the same as cloning. The use of “dd” will not work as expected unless the partition is read-only during the dd read. The clone mechanism guarantees read-only because the Jetson is in recovery mode and an external tool is doing the reading (sort of a substitute for dd).
The “flash.sh” program (command line, found in one of the subdirectories of “~/nvidia/nvidia_sdk//Linux_for_Tegra/”) can be told to “reuse” the existing image (the “-r” option) during flash. If it turns out you’ve run the flash before, then this will reuse the sample rootfs image; if you’ve replaced that with a clone or dd, then the rootfs becomes the clone or dd instead.
I am unsure of command lines for cloning the eMMC type of Nano module, but this should do the job if someone can comment on clone/flash on command line for this version of the Nano.
Note that a clone provides both a “backup.img” file and a “backup.img.raw” file. The “raw” file is larger, but is much more useful. The “backup.img” file is a “sparse” file, and is much smaller, but can only be used for flashing (it can’t be examined or edited the way a raw image can). When either of these are placed in the “Linux_for_Tegra/bootloader/” directory with file name “system.img” the flash will succeed. The only reason the smaller “sparse” file is used is that it takes less time to flash this.
To reemphasize, the flash with the “-r” option will still flash the non-rootfs files, but the actual rootfs will be your file instead of the default sample. These files must use the same release of software.