Short backstory: I have never done anything with mdadm before and am in charge of maintaining an ubuntu 16.04 server with a software RAID 1 based on mdadm. Recently I updated grub and was prompted to select which disks grub should be installed on.
I chose to install it on both /dev/sda and /dev/sdb because I have read that it does not matter to mdadm and is better to install GRUB on both disks.
Currently I am trying to update the linux image, but I get the following error during the post installation script:
grub-probe: error: disk `mduuid/[uuid here]' not found.
The installation fails after this message.
This is the complete output of the post installation script:
Examining /etc/kernel/postinst.d. run-parts: executing /etc/kernel/postinst.d/apt-auto-removal 4.4.0-72-generic /boot/vmlinuz-4.4.0-72-generic run-parts: executing /etc/kernel/postinst.d/initramfs-tools 4.4.0-72-generic /boot/vmlinuz-4.4.0-72-generic update-initramfs: Generating /boot/initrd.img-4.4.0-72-generic run-parts: executing /etc/kernel/postinst.d/zz-update-grub 4.4.0-72-generic /boot/vmlinuz-4.4.0-72-generic Generating grub configuration file ... grub-probe: error: disk `mduuid/[uuid here]' not found. run-parts: /etc/kernel/postinst.d/zz-update-grub exited with return code 1 Failed to process /etc/kernel/postinst.d at /var/lib/dpkg/info/linux-image-4.4.0-72-generic.postinst line 1052.
I have no idea how to fix this and can't seem to find anything after hours of googling. Please also note that I didn't ever reboot the server after the first grub update that I mentioned in the first paragraph of this post.