Striker is right I'm "out of the country" (not at home), fortunately not out of this world.
Will have access to the forum from time to time.
You can not implement a new mtd partitioning into an existing old installation.
But you can update by flashing via "dd" or "mtd write".
First check your current mtd partitioning with "cat /proc/mtd".
For WNR845T it should be:
dev: size erasesize name
mtd0: 00100000 000x0000 "kernel"
mtd1: 00660000 000x0000 "rootfs"
Then use the info from post #340, paragraph "Flashing in Linux / with same kernel mtd size".
Using "mtd write" would even be better than "dd", because I do not provide padded images anymore.
But if you want to use "dd" with a padded image, than above that paragraph is the code for "create_images_WRT350Nv2.sh" which shows how to create a padded image.
And at the beginning of that post is an example how to split a squashfs release image ("openwrt-wnr854t-squashfs.img").
Read the mentioned posts, play around a little bit in linux with the images and "dd" (or in your router's /tmp dir).
If you feel comfortable you may decide to flash in linux via "dd" or "mtd write".
And I always recommend to document your steps, helps to find your own bugs and create good bug reports (what file, md5sum check, what commands, error messages, file sizes, file compares, etc.).
Process sequence: download, md5 check, upload, md5 check, split, flash