How to add (and persist) menu entries to GRUB menu?

[C-Duv]

I want to setup multiboot on my computer using MiniOS as a base (and it's GRUB) with other OS (such as LibreELEC).

I've booted MiniOS from an USB then installed it on the internal hard drive (using the provided tool).
With GParted I have created the partition and I know the GRUB menuentry to add for LibreELEC but I can't make my changes persist.

Changes to both files /etc/minios/grub.cfg and /run/initramfs/memory/changes/etc/minios/grub.cfg are being reverted on shutdown.

What's the correct way to do so?

I could not find any documentation on how to "update GRUB" on MiniOS.

[C-Duv]

OK, it looks like the correct file to update is /run/initramfs/memory/data/minios/boot/grub/grub.cfg, after a reboot it's content gets "propagated" to /run/initramfs/memory/changes/etc/minios/grub.cfg (and thus to /etc/minios/grub.cfg also).

Note: It needs to be made writable first: chmod u+w /run/initramfs/memory/data/minios/boot/grub/grub.cfg.

[crim50n]

You only need to edit the files in /etc/minios, they will automatically replace the original files on the flash drive when you shut down the system.

[C-Duv]

I'll double-check but I'm pretty sure it did not worked.

[crim50n]

Okay, I'll check it out.

[crim50n]

Yes, indeed, changes must be made to the configuration file on the flash drive. The file in /etc/minios is for rebuilding the ISO.