How do I run update-grub from another Partition or a LiveCD?
As you know my Setup, I will shortly explain again. In my Powermac G5 there is an SATA-SSD as a replacement for the old spinning Apple HDD. On this SSD I installed Mac OX 10.5 and also Debian SID for PPC, to get the Partition-Scheme and GRUB installed.
I also built in a NVMe-SSD with 1 TB because the Powermac11,2 has PCI-Express Slots like it is standard nowadays. The OpenFirmware in the Powermac doesn't know what an NVMe-SSD is and therefore can't recognize it or boot it. Also Mac OS X 10.5 doesn't see the device. The technic is too young and there are no drivers, that is the reason for that.
But lucklily, Linux has the drivers for that. And that's the reason for my Setup. Boot Grub from SSD because that can the Powermac. Than load the things you need for NVMe and boot the linux off the NVMe-SSD.
I have 4 Linux on that NVMe-SSD and that works great. But it is a problem to update the Grub Bootloader everytime there is a new kernerl or something other changed. Long story short, here I will tell (me) you, how to update grub via chroot.