Configuring/using grub with grub-install and grub-mkconfig

[Chris Green]

I have been searching around (and asking questions) about how to add a
separate /boot partition.  As a result I have become steadily *more*
confused about the relationship between grub-mkconfig and grub-install.

So, is there a good tutorial anywhere about all this?  Much of what I
have found goes into detail about how grub2 is different from the
original grub but doesn't really give details of how to use grub2.

I just need to reconfigure my system to use a separate (small) boot
partition and a large (non bootable from BIOS) main partition.

So, currently I have:-

    /dev/sdb1         112515  15996     90782  15% /
    /dev/sdc1         938771 275489    615589  31% /home

with xubuntu 19.04 booting from /boot on /dev/sdb1.

What I want to do is add /dev/sda and install /boot on that partition.


So I can mount /dev/sda1, no problem there.  So what do I do next?
Do I run grub-install?  Do I run grub-mkconfig?

I am fairly unix/linux aware (like 40 years aware!) and have done
quite 'techy' things in my time like build custom kernels and such but
this has got me really confused.

I suspect what I may have to do is try this out on a spare system (I
have a few PCs around which are redundant) and "see what happens".
However it does seem rather poorly documented.

-- 
Chris Green