What error 21 might mean is explained here: http://www.supergrubdisk.org/wiki/GrubOnRemovableExternalHardDiskNotBooting and this url might be also useful: http://www.supergrubdisk.org/wiki/GrubHardDiskOrder
The main problem here is that Grub relies on the BIOS for knowing hard disk order. So there are several things here: * Ubuntu installer when finding two hard disks it does not prompt the user to assign one hard disk to hd0 (first bios hard disk) and another hard disk to hd1 (second bios hard disk). This is problematic even when using the uuid command. Because root (hd1,2) setup (hd0) commands might be run, when root (hd0,2) setup (hd0,2) with another device mapping is needed. * grub2 will have a native IDE controller and a lot of features that will make it more BIOS independent but it is not mature enough. * Whenever people install Ubuntu into an external hard disk, even if everything is ok, if they reboot without the external hard disk connected they will get an error 21. So... How do you fix it? Adding a Windows boot entry to Ubuntu that includes my fix to chainload grub from a second hard disk? (Found here: http://www.supergrubdisk.org/wiki/Howto_Boot_Grub_from_windows). That's not ok for non-Windows users. * People do not know often how to learn if BIOS detects their hard disks or not. I mean, this error 21 bug thread will grow and grow with no apparent solution till maybe grub2 appears. -- Grub - Error 21 returned https://bugs.launchpad.net/bugs/8978 You received this bug notification because you are a member of Ubuntu Bugs, which is a direct subscriber. -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
