Grub won't detect second MX Linux installation

[DR77]

@fehlix
If the issue is the encrypted root partition why grub won't detect it when it's unlocked and mounted?

@Charlie Brown
Windows 7 is also installed on the second disk, but grub finds it. I added 'GRUB_ENABLE_CRYPTODISK=y' to '/etc/default/grub' but it didn't help.

[fehlix]

@fehlix
If the issue is the encrypted root partition why grub won't detect it when it's unlocked and mounted?

Yes, as explained: update-grub is using os-proper (as a helper tool), and os-prober will only "construct" a menuentry,
for "found" installed linux system. It will ignore any boot partition, if it cannot detect the base /-root partiton.
And for some unknown reason, os-prober ignores unlocked "root" partition. In theory it would be possible,
but I guess os-prober was build in mind, to run without any user interaction to prepare to un-lock root first.
So, it will simple skip luks partition.

@Charlie Brown
Windows 7 is also installed on the second disk, but grub finds it. I added 'GRUB_ENABLE_CRYPTODISK=y' to '/etc/default/grub' but it didn't help.

The tool os-prober is used to find already existing grub-installation (or other non grub-installations like W7), when running update-grub.
The parameter GRUB_ENABLE_CRYPTODISK is intended for generating the grub core image (during grub-install.)
So nothing what os-prober has todo with.