Using your own image

If you already have a NextZXOS SD-card image, point JNEXT at it:

jnext --sdcard /path/to/my-image.img

An explicit --sdcard always wins: it is used as-is, and no download is ever offered or performed. In the graphical version you can also mount one from File > Mount SD Card Image, and set a permanent default in Preferences (chapter 4).

The image is opened read-write, and whatever the emulated machine writes to the card is kept. Booting is not one of those things: reaching the NextZXOS welcome screen and the menu writes nothing at all, and leaves the image byte-identical. What changes it is file work done through NextZXOS — saving from NextBASIC, a DOS command such as .mkdir, the Browser copying or deleting something, or a program writing a file. Those changes persist into later runs, exactly as they would on a real card, so two runs sharing one image are not independent once one of them has written.

Add --sdcard-readonly when a run must not disturb the image: the emulated machine then sees a write-protected card and the host file is never touched.