It’s very much possible to write the sd card from CoreELEC.
It does however involve using ssh, and some linux command line stuff that could cause you grief that would be hard to recover from if you make a mistake. So make sure you read the instructions once before doing this, and don’t just blindly copy and paste your way through without reading anything else.
I will use the amlogic-ng nightly build from the December 29th as an example image. be sure to change the img name in the relevant commands below if you use a different build.
1.) ssh into the device.
2.) get the disk image to burn. (Replace the link with the correct one for the image you wish to use)
wget https://relkai.coreelec.org/CoreELEC-Amlogic-ng.arm-9.2-nightly_20191229-Generic.img.gz
3.) decompress the disk image. (replace the file name with the one you just downloaded)
gunzip CoreELEC-Amlogic-ng.arm-9.2-nightly_20191229-Generic.img.gz
4.a) Important!!! Verify that internal emmc does not have the same name as we are expecting the microsd card to have.
ls
ls /dev/mmcblk1
If the output of this command is anything other then
ls: /dev/mmcblk1: No such file or directory
when the microsd card is not inserted then DO NOT CONTINUE with these instructions.
4.b) insert micro sd card.
5.) unmount the micro sd card. (CoreELEC will auto mount removable media, and you can’t burn the image with the device mounted)
umount /dev/mmcblk1p?*
6.) burn the image to micro sd card. (make sure you replace the name of the image if you are using one different then in the example)
dd if=CoreELEC-Amlogic-ng.arm-9.2-nightly_20191229-Generic.img of=/dev/mmcblk1 bs=1M conv=fsync
7.) then just to be sure everything is written and the device doesn’t still have anything waiting in a buffer
sync
8.) copy the dtb file.
CoreELEC should auto mount the filesystem for the newly burned card.
cp /flash/dtb.img /var/media/COREELEC/dtb.img
(note if you are burning this card for a different device or burning a different build of CoreELEC then what you had on the usb drive be sure to copy the correct dtb for that device instead. They can be found in /var/media/COREELEC/device_trees )
9.) unmount the sd card
umount /dev/mmcblk1p?*
10.) power off device. remove usb drive. you can now boot from the micro sd card, just like if you had used a computer to burn the card.
11.) restore backup made of previous usb install on to microsd card install.