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I have a brand new installation that I'm trying to install Grub2 onto 6 disks, in a Linux Software Raid 5 array. I am using mdadm to build the array. I would think the correct partition to install grub2 on would be md0, but it fails to install, there. I created a /boot partition that goes to /md0p4, but it won't install there, either. I followed several forum posts and guides on how to install grub, but nothing works. I can't install it to the root of every /dev/sdx. One forum post said that Grub2 should have no issues with SW Raid. There aren't really any topics that help, here. Does anyone know anything about installing grub2 on software linux RAID 5?

Ubuntu 16.04

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  • GRUB is supposed to be loaded by the BIOS or the EFI firmware; as a consequence, it must be installed on a device from which the computer system can boot. Are you sure that your system can boot from a software RAID5 array? How does it do that? – AlexP Feb 11 '17 at 1:22
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Assuming this is a bios booting computer and not EFI, and that you partition each individual disk and create a raid type partition and use those partitions to build the raid array, then you install grub to each of the individual disks in the array so that any one of them can boot the system using any n-1 disks that are still present to access the array. You can do this by running sudo dpkg-reconfigure grub-pc and checking all of the individual disks ( /dev/sda, /dev/sdb, etc ) to install grub to.

Note that the graphical standard installer will only allow you to pick one place to install grub to, so you either need to use the server installer, or manually run sudo dpkg reconfigure grub-pc afterwards to install grub to all of the disks.

Also do not forget that with a RIAD5, only two disks need to fail to render all of your data lost, and with 6 disks total that is not entirely unlikely. If your concern is maintaining system uptime then you might want to use RAID6, which can tolerate two disks failing, but in any case, RAID is no substitute for backups, so either way, you still need to back up your data otherwise to make sure that you don't lose it should something go wrong, which it inevitably will.

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  • Does each disk need to have its own small partition, to install grub to? sda1, sdb1... Then the actual raid is sda2, sdb2... – talkinggoat Feb 11 '17 at 14:26
  • @talkinggoat, if the disks are partitioned with MBR ( so less than 2 TB ), then no. If they are partitioned with GPT ( must be if they are > 2 TB ), then you need a 1 mb bios_grub partition for grub to install on them. – psusi Feb 14 '17 at 14:54

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