I thought it would be easy but so far it's impossible.

I just want to install Ubuntu 20.04 (or any Linux) onto a 500GB laptop
internal HDDl which is _temporarily_ connected via a USB adapter to my
Windows 10 Home PC as an external HDD.

I formatted (exFat and then NTFS) the 500GB HDD but I can't figure out how
to install Linux on it from Windows 10 so that the

I do NOT have a USB stick!
I have to get this done tonight.
What I have is a Windows 10 laptop with plenty of disk space on drive D:

So I put the Linux ISO on both drive D: and drive E: (where E: is the USB
drive) but I can't figure out how to get Linux to install as a boot disk
for another computer (which I don't have) with my configuration.

I even tried https://unetbootin.github.io and I put that executable
(unetbootin-windows-702.exe) on both the D: drive (which belongs to the
laptop) and the E: drive (which is the external USB drive I want to install
linux on so that it can be inserted into another laptop and it will boot to
Ubuntu on that second laptop).

I even put the Ubuntu ISO on both the D: and E: drives, and yet the darn
unetbootin doesn't _see_ the E: drive even though Windows has no problem
seeing it.

How the heck can I install Ubuntu on an E: drive (which is tied by a USB
cable using an adapter) from Windows (which has a C: & D: drive).

I don't want the original computer to dual boot. I just want to put a
bootable Linux on the external HDD. What's the secret that I don't know?

On 11/16/2021 1:39 AM, harry hornsley wrote:
> I thought it would be easy but so far it's impossible.
>
> I just want to install Ubuntu 20.04 (or any Linux) onto a 500GB laptop
> internal HDDl which is _temporarily_ connected via a USB adapter to my
> Windows 10 Home PC as an external HDD.
>
> I formatted (exFat and then NTFS) the 500GB HDD but I can't figure out how
> to install Linux on it from Windows 10 so that the
>
> I do NOT have a USB stick!
> I have to get this done tonight.
> What I have is a Windows 10 laptop with plenty of disk space on drive D:
>
> So I put the Linux ISO on both drive D: and drive E: (where E: is the USB
> drive) but I can't figure out how to get Linux to install as a boot disk
> for another computer (which I don't have) with my configuration.
>
> I even tried https://unetbootin.github.io and I put that executable
> (unetbootin-windows-702.exe) on both the D: drive (which belongs to the
> laptop) and the E: drive (which is the external USB drive I want to install
> linux on so that it can be inserted into another laptop and it will boot to
> Ubuntu on that second laptop).
>
> I even put the Ubuntu ISO on both the D: and E: drives, and yet the darn
> unetbootin doesn't _see_ the E: drive even though Windows has no problem
> seeing it.
>
> How the heck can I install Ubuntu on an E: drive (which is tied by a USB
> cable using an adapter) from Windows (which has a C: & D: drive).
>
> I don't want the original computer to dual boot. I just want to put a
> bootable Linux on the external HDD. What's the secret that I don't know?
>

+-------+--------------------------+--------------------+
| MBR | System Reserved (Active) | C: Win10 | /dev/sda
+-------+--------------------------+--------------------+

+-------+--------------------------+--------------------+
| MBR | Linux Slash EXT4 | Linux Swap 1GB | /dev/sdb (on USB bus)
+-------+--------------------------+--------------------+

To do this:

1) Boot either a Linux DVD or a Linux USB Stick.

2) Custom install. Define Linux Slash and Linux Swap.
You define an EXT4 say, claim the mount point is "/" and
that is the partition where the OS will go. The thing
designated as mount point "/", is where 7GB of files might go.
A 35GB partition for "/" might be a comfortable size for a
naive user (still enough room for kernel build, but you don't
have to build kernels to be able to email and browse).

3) The trick is, the grub_install step. Custom install may
have a step which asks you how you want to control that.
Grub_install needs to know two things - which MBR needs
first stage Linux boot, which partition number (/dev/sdb1)
needs stage two Linux boot. Stage 1.5 is the slack area
between the MBR and the first partition.

Grub_install, also scans the machine for OSes. If OSProber (about 23KB)
is present on the install media, the scan includes scanning for Windows.
If you artificially remove OSProber from the install media
(would require editing squashfs file on the install media),
then it's like poking the installer in the eye with a stick,
and it is then "blinded to Windows". But nobody does that.
Some distros ship without OSProber, which is why you need to
know which file does it for you. If you "can't get Windows
into the menu", check that an OSProber is installed.

Thus, the boot menu *will* include both Linux and Win10,
if you don't modify the install media (which is pretty
silly, but hey). I've modified media before, but it is
not something I do regularly.

The other command is update_grub, which is run any time the kernel
version changes (and some stuff is getting rebuilt, like the boot
menu needs to know about kernel). During the update_grub, which
you can do manually, when that USB device is plugged into another
computer, the Win10 disk will no longer be present. The update_grub,
when osprober runs, the Win10 disk won't be present on the
other machine, so Win10 will be removed from the menu.
In other words, the runtime environment can be resolved, when
you move the materials to the other machine, and not before.

On Windows, a similar opportunity exists when you use the
Macrium boot repair on the Rescue CD. It scans for all drives,
and attempts to put all boot materials in the Windows boot menu.
If a second or Nth drive was missing, then the boot menu
would be tidied up during a boot menu rebuild and fewer items
would be present.

Summary: You're *mostly* good to go.

You are violating the First Law Of Install. The Win10
drive should be unplugged, so only the external is present.
This is "Safest". However, the installer on Linux *does*
have the tools, to do this without unplugging anything.

Multibooting is a "learn while you earn" exercise. You
learn by making mistakes. If you back up the entire Win10
drive to an external (third) hard drive, then even if you
make big mistakes, no harm done. Just restore using your
Macrium Rescue CD or equivalent. So for example, in a moment
of clumsiness, you overwrite the Win10 disk. The installer
has a menu item to "blow away" entire disks. Do not underestimate
the damage this can do. While I was learning to multiboot,
I destroyed two disks that way. But, I'm learning :-)

There have been problems (and surprises) about where the
grub_install puts stuff in the past. The BIOS/OS used to have
problems with enumeration and numbering. The booting disk
at the time, might have been "Disk 1" for no particular
reason, and you could then, never trust the disk identifiers.
(Like, even if the installer had the power-user option to
select which MBR, you could not trust the disk labels.)
Back then, this made it hard to predict, where the GRUB
materials would end up (two disks, cross linked, the result).

If you don't violate the First Law of Install, then nothing
bad could happen to you. If only the install target disk (USB)
is present, the install materials can't "splatter" anywhere, if
innocent disks are unplugged before you begin as a precaution.
Again, I learned this by doing, and after a while, it was just
better to remove the fluff from the machine, so it doesn't get damaged.

I've pulled the SATA SSD a number of times, from the laptop,
as part of Safety First.

Good luck,
Paul

Are you able to install VirtualBox?
You could use USB passthrough to pass the USB attached HDD to the VM and
then boot the VM with the Linux ISO and install the OS.