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There is a way to indicate to grub to install on a device MBR by UUID instead of using /dev/sdX ? I'm setting a external eSATA hard disk with NixOS, and obviusly, the hard disk not would be always the same /dev/sdX device ?

I see that I can config it with boot.loader.grub.device = "/dev/sdX", but could set it to something like "/dev/disk/by-uuid/...." ??

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  • Did you try it? What were the results?
    – user
    Feb 5 '15 at 9:42
  • I'm just trying it ... /dev/disk/by-uuid/XXX not would work as on my case, the hard disk alone not have a UUID. But /dev/disk/by-id/XXX looks that could work. nixos-rebuild dry-run don't output any error, so I would try it now.
    – Zardoz89
    Feb 5 '15 at 18:15
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grub-install /dev/by-uuid/XXX not would work becasue the whole hard disk not gets a UUID (at least on my machine). Instead, we could use /dev/by-id/XXX that is generated using the serial number of the hard disk.

On NixOS configuration file would be :

boot.loader.grub.device = "/dev/by-id/XXXX"
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try grub-install "UUID=700C663F-4183-4A8D-BAC2-EE34E5518B9C" /dev/sda0 UUID is "/" partition sda0 is "/" device Source is grub2 manual /dev/disk/by-uuid/ does not work because this directory does not exist until is booted it is preferred to use partuuid as this dos not change with reformatting- uuid changes with formatting

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  • As I said "not would work becasue the whole hard disk not gets a UUID (at least on my machine).". Using /dev/by-id/XXXXX just works fine on my case. Also, I'm configuring nixos, so I need to setup it on text config file, not run directly grub with a parameter.
    – Zardoz89
    May 13 '15 at 7:07
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Yes, modify /boot/grub/menu.cfg

root=/dev/disk/by-uuid/whatever-blkid-outputs-placed-here

...give it a whirl.

For example

set root=/dev/disk/by-uuid/'3a2adf19-8685-483c-9889-1b4d56788486'

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  • I was thinking this is useful for the times you use a LiveCD to recover an installation and for some reason the LiveCD become /dev/sda1, and the internal HD is assigned /dev/sdbX...except when you re-boot and it re-verts to the re-verse. Assign a UUID and be done with it.
    – Nodak
    Feb 5 '15 at 10:16
  • No no no .. You don't understand me. I don't asking if I can set the /boot partition by UUID (I did... piece of cake!). I'm asking how INSTALL GRUB on a disk using the disk drive UUID ... on other words ... I could do "grub-install /dev/disk/by-uuid/...." ?
    – Zardoz89
    Feb 5 '15 at 10:45
  • Oops, sorry. Then I'll echo Michael Kjörling, above...did you try it? The worst that can happen is you would learn something.
    – Nodak
    Feb 5 '15 at 10:55
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No, you cannot grub-install /dev/disk/by-uuid/foo. This is not saying it is impossible, one might concoct a method, but it is impractical at the least.

UUIDs (universally unique identifier) are practically unique identifiers for partitions, and not the device itself. That is partitions have a UUID, but the location of the MBR that grub-install addresses does not have a UUID.

If you generate a UUID for the device (e.g.,uuidgen /dev/sdb) you then encounter a device.map problem within GRUB. grub-mkdevicemap fails to rectify the problem automagically.

If you grub-install /dev/disk/by-uuid/de305d54-75b4-431b-adb2-eb6b9e546013, for example, you will receive errors like

grub-install: warning: File system `ext2' doesn't support embedding.
grub-install: warning:  Embedding is not possible.   GRUB can only be installed in this setup  by using blocklists. <blah, blah, blah>

...and so it goes.

More info can be found https://unix.stackexchange.com/questions/174206/warning-file-system-ext2-doesnt-support-embedding-but-my-system-isnt-emb

This was a fun experiment. Thanks.

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