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When installing Ubuntu 12.04 to an external HDD using Ubiquity, it installs GRUB2 to that HDD. Such installation works fine on the machine on which it was created, but on any other machine everything just hangs up after loading the initial ramdisk. The machine shows black screen and no disk activity goes on.

I suspect this is caused by some configs being dependent on "global" device enumeration which is different on different machines, or something else gets machine-dependent. How do I avoid that? Shall I generate a more generic initial ramdisk somehow? Or perhaps using syslinux instead of GRUB2 will help?

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Actually be careful. Ubiquity will usually default to installing grub to /dev/sda regardless of which drive you are installing to. If you change the drive to the correct one, then select that drive in the boot menu or BIOS to boot off, it should work in all cases. You can install grub2 to the correct drive after the fact but you will need to chroot into the USB drive to update the grub boot menu correctly. – fabricator4 Jan 11 '13 at 8:47
Actually, Ubiquity may default to the external drive in many cases, even if it's a LiveUSB from which the system is being installed. I guess this is a bug. But I'm sure I've installed GRUB2 to the external HDD :) – Shnatsel Jan 11 '13 at 9:17
  • If you installed ubuntu and grub in external HDD,

    just open up the bios and choose externel HDD as primary boot device. It will boot.

  • If you have installed ubuntu in external HDD and GRUB in internal HDD,

    you need to install grub in external HDD and follow whatever I said above.

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This gets me to the GRUB menu and it even tries to boot from the right partition! However, now it hangs up just after loading the initial ramdisk. I've updated the question with this problem. – Shnatsel Jan 11 '13 at 9:35

While installing Ubuntu on external HDD, please select grub location to external HDD mostly /dev/sdb..

I am running Ubuntu 12.04 500GB USB HDD. I have tested running Ubuntu on different NB & it is running successfully. Note: Need to select first boot device as external HDD, when you connect this on other machines.

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I did, it shows GRUB menu but fails right after loading the initial ramdisk. – Shnatsel Jan 11 '13 at 10:53

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