If you disconnect sda
Can you boot entirely from the USB external?
This might come into play;
if os-prober from the primaries' grub is picking up that "botched" install (??).the internal drive has 12.04 32 bit and a botched 12.04 64-bit
I am presently triple booting, and how I manage my grub is:
I have grub installed for each install onto the MBR of each disk, ok, now I run "update-grub" on EACH install, and on my primary (the os that is controlling booting) I run install "sudo grub-install /dev/sda" as a last step. Because my primary controlling OS is located on that first hard drive (sda). The control grub picks up all the other operating systems,
The fallacy of my way is that each time there is a update to the kernels, I must go through that routine each time; to get my grub boot menu back in order (10 minutes !).
Note ersatzsplatt, though I have 3 OS installed, all share a single swap partition. Hint . But as you are travelling with one of the drives ya do need to keep a swap on that traveling drive.Code:sysop@1310mini:~$ sudo blkid /dev/sda1: LABEL="1310mroot" UUID="3a47f1f1-ed1f-4134-b6aa-be101a7d97b4" TYPE="ext4" /dev/sda2: LABEL="1310mhome" UUID="29a6fc4f-ff12-4cac-8eb1-e98e50f1107f" TYPE="ext4" /dev/sda5: UUID="192a4783-56fa-4fd0-a62f-c45a14c08482" TYPE="swap" /dev/sda6: LABEL="DATA" UUID="3ad091a1-5036-463b-ba4e-88e98e41b07a" TYPE="ext4" /dev/sda7: LABEL="LUBU1204" UUID="4e6cd96d-49bd-47f0-9dfe-8eeebad4cf9d" TYPE="ext4" /dev/sda8: LABEL="1310mvar" UUID="136af805-5758-4880-acc4-0e1d35e2c266" TYPE="ext4" /dev/sdb1: LABEL="my_stuff" UUID="6a24777c-8191-4230-81f1-376f31b321e5" TYPE="ext4" /dev/sdc1: LABEL="ubie1204" UUID="5bae8c40-b15d-42f8-9fc9-0cf087f338d4" TYPE="ext4" sysop@1310mini:~$
my little bit to help
carl4926, I don't think I would be able to boot from the external drive if I disconnected from sda, because grub would then reference the external drive as sda and would look for sdb. You are really asking something related to the question I asked in my last post, which is beyond the scope of the narrow question I'm asking. The question I'm asking is how to get an updated grub on the external drive I'm booting from.
The question which seems beyond the scope of that question, is how to boot from the external drive on any system regardless of the number of drives already connected to that system.
Bashing-om, you seems to have an interesting use case. I'm still not sure how I can update the grub on my external drive though.
If the external is sdb
Check it is seen as sdb in fdisk and gparted
But I think you tried
The problem I think might be that sdb is not /devCode:sudo grub-install /dev/sdb
but rather (is it) /var/run/media/youruernmame/device-id
There are a lot of tutorials about manually adding a grub bootloader entry...
But if you want to boot from your external drive treat it like a usb stick:
make it bootable with syslinux ... right?
et al; Good points.
I failed to mention that the OS/kernel placement in the grub menu is paramount. That primary boot system must be the 1st entry to default to.
I would also insure I was using the device's unique UUID.
Cavsfan has authored a great tutorial on maintaining one's grub:
drs305 is our guru on anything grub:
It is doable
and you can do this
Are you absolutely certain that you are "booting" the external drive, or is it possible that grub on the internal drive is actually booting to it (and may be why kernels are missing)? With some computers (particularly Dell), even if you change the device boot order in CMOS, you may still need to press a hotkey in the BIOS splash screen to select the drive to boot from, for anything other than an internal drive.
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