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Grub 1.99 on external USB disk

From: Nordgren, Bryce L -FS
Subject: Grub 1.99 on external USB disk
Date: Fri, 22 Jun 2012 20:50:45 +0000



I’m trying to get grub 1.99 to boot NixOS from an external USB disk. Everything works fine when installed on an internal disk, at least on other systems.


Symptom: System says “welcome to grub”, then “error: prefix is not set”, then freezes. No grub rescue prompt. Can’t ctrl-alt-del. Can’t type at all. Must power off.


System (@time of grub-install):

HP2710p laptop

/dev/sda : encrypted internal drive (work)

/dev/sdb: USB flash drive (boot drive) containing NixOS installer

/dev/sdc: 500Gb external USB disk. Two partitions, only /dev/sdc2 is relevant (400Gb). The first partition starts at ~1M, leaving room at the beginning of the disk. Both partitions are ext3.


Install command:

grub-install –modules=”ohci uhci usbms ext2” –boot-directory=/mnt/boot /dev/sdc


Fdisk –l output and grub.cfg are attached. (/dev/sdd is the USB stick used to bring these files over to my workstation where I’m writing this email. It wasn’t there when grub-install was run.)


Note that I get a different symptom if the “—modules” option is omitted above. It says “welcome to grub”, then “(hd0) out of disk”, then gives me the grub rescue prompt. Performing an “ls (hd0,msdos2)/” at the prompt lists the first two directories or so, then errors with “(hd0) out of disk”. “/boot” is not among the directories listed. Doing “ls (hd0,msdos1)/” completes successfully.


The attached “grub.cfg” attempts to set root and prefix using filesystem labels and/or uuid. Neither worked.


Apologies if this has been asked before. I was unable to locate this symptom in the archives.



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Attachment: grub.cfg
Description: grub.cfg

Attachment: fdisk.txt
Description: fdisk.txt

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