I tried the given two files for RockOS by doing a cat file1 file2 filezip.
Then unzipped it and used create startup disk in Ubuntu 24 with the target drive in an external reader. It worked but the xwindows hung. I made a mess of it over ssh.
Next I downloaded sdcard-rockos-20250729-015830.img.zst
from here https://fast-mirror.isrc.ac.cn/rockos/images/generic/latest/
The server was real slow.
I then unzstd sdcard-rockos-20250729-015830.img.zst
(won’t work with normal zip program, must use unzstd)
I got sdcard-rockos-20250729-015830.img
I used create startup disc again (you have to pull down the type selector from cdrom to drive image) Be careful that you have selected your proper destination drive!
Inserted the drive and booted… there was a bootloader in the computer flash already.
