Install Ubuntu to Loopback Image File

[amanisdude]

Hi all!

The title says it all. I want to install Ubuntu (specifically Lubuntu for now, but maybe another flavor later) to a raw loopback image file (IMG, not ISO).

The image file will reside on my FAT32-formatted USB stick at the maximum allowed size: 4,294,967,295 (or 2³²−1) bytes. (FAT32 is for Grub4Dos compatibility.)

I know Wubi (https://wiki.ubuntu.com/WubiGuide)/Mint4Win (http://usbtux.hostzi.com/mint4win) does something like this inside Windows, so I know it's possible; I've just never found a good resource that clearly documents the process.

Any help would be much appreciated! Thanks!

-amanisdude
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Note: This question was asked before on this thread but was never answered: http://ubuntuforums.org/showthread.php?t=1289533
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[dino99]

might help :p

http://askubuntu.com/questions/128995/grub2-loopback-booting-ubuntu-server-iso

[amanisdude]

Hi dino99,

Thanks for the reply. :D Unfortunately, I don't think the link quite answers my question. I am trying to install Ubuntu onto a raw disk image file similar to the one Wubi, Lubi, and MINT4WIN creates (http://en.wikipedia.org/wiki/Wubi_%28Ubuntu_installer%29) on an existing filesystem, not to an ISO.

The main advantage of this is that the host file is easily editable by the operating system, unlike ISOs which have write issues when live.

My main problem is getting the Ubuntu installation onto the image file in the first place, not necessarily booting it (which I already do with ISOs on my USB stick). Also, GRUB4DOS is actually a build of Grub1, not Grub2.

If you have any thoughts on how to do this, please let me know. The answer may well be in the link, but I just don't see it. Thanks again!


-amanisdude
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[oldfred]

You can use wubi and boot with grub2.

I do not think this was a recommendation, but just a proof that it can be done.

See also this thread, you technically do not need windows to use wubi.
Posts by meierfra. to use grub2 to directly boot wubi
http://ubuntuforums.org/showthread.php?p=8903013

[amanisdude]

Thanks for the reply OldFred!


Hmm... It feels like I'm not fully being understood here. Let me try and clarify my question. :)

→ I have a bootable 32GiB USB Flash Drive
→ The flash drive uses Syslinux to chainload Grub4DOS
→ Grub4DOS then boots one of several ISO files on the flash drive as if they were CDs (See: Multiboot ISOs (http://www.pendrivelinux.com/tag/multiboot-iso/))
→ I want to do the same with a dynamic installation of Ubuntu on a virtual disk image file on my flash drive, not hard drive
→ (i.e., I want Grub4DOS to boot a virtual disk file on my USB Flash Drive as if it were a hard drive partition, not an ISO which acts more like a CD)
→ If I were to do this, I would probably have no trouble booting the file with the existing Grub4DOS bootloader on my flash drive
→ The problem is getting Ubuntu installed on the virtual disk file in the first place


Are you suggesting that I install Wubi then take the root.disk image file it creates and copy it over to my Flash Drive? I was hoping there would be a more elegant solution, but I suppose it is doable.

The only issue is that I already have Wubi installed in Windows, so I would have to archive the existing installation, reinstall Wubi, shrink down the resulting root.disk file to the maximum file size allowed by FAT32 (~4GiB), boot into it, remove swap.disk from /etc/fstab, copy root.disk over to my USB Flash Drive, link it to Grub4DOS, and restore my original Wubi installation. Yuck!


Does anybody have an idea on how to do this in one fell swoop (or at least several feller swoops)? I mean, assume I am someone who does not have nor wants to install Wubi and does not want to mess with existing HDD bootloaders. How would I go about it this way?

Thanks for all the help, guys! You guys rock!


-amanisdude
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[oldfred]

I have not tried virtual installs, just dual booting.

But why not a full install to your flash drive then. I have a full install of 12.04.2 on my 16GB flash in an 8GB partition and 8GB for data. Some minor changes to reduce writes, not real speedy but functional. Once system & apps are in memory not really different than my hard drive installs.

Pros & cons of persistent install over direct install to flashdrives - C.S.Cameron
http://ubuntuforums.org/showthread.php?t=1655412

[amanisdude]

I have not tried virtual installs, just dual booting.

But why not a full install to your flash drive then. I have a full install of 12.04.2 on my 16GB flash in an 8GB partition and 8GB for data. Some minor changes to reduce writes, not real speedy but functional. Once system & apps are in memory not really different than my hard drive installs.

Pros & cons of persistent install over direct install to flashdrives - C.S.Cameron
http://ubuntuforums.org/showthread.php?t=1655412

Thanks for your help, Paul. :D I agree with all the points in that thread, which is why I opted for a multiboot persistent image install on my pen drive.

My main reason for a virtual install is portability. If I decide to move the install to another medium, it's pretty simple; all I need to do is move the file and configure the new bootloader.

The second reason is because the flash drive has so many other operating systems on it in the form of Live CD ISOs that a virtual install makes the most sense. Furthermore, it is easy to make a backup snapshot of the installation for my archives in case I mess something up, or to make a quick temporary clone of the install.

At any rate, do you know if there might be a tool to make a virtual install like I'm looking for, or someone who I might be able to ask? Maybe I could somehow pipe the output file of Lubi (http://lubi.sourceforge.net/lubi.html) into Bubackup (http://lubi.sourceforge.net/bubakup.html) and do it that way, or just maybe run Bubackup (http://lubi.sourceforge.net/bubakup.html) in a temporary virtualized instance and just copy the resulting image file? Thanks for the help, guys! ^_^

-amanisdude
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[amanisdude]

[[ post temporarily revoked until fully tested ]]
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Whelp, I finally did it. I can't say it was an elegant solution, but it worked. :)

First, I used Virtualbox to create a new virtual machine with a new virtual disk (*.vdi) file a bit smaller than the maximum size allowed by FAT32(4,294,967,295 bytes). I then installed Lubuntu onto the VDI using the Lubuntu ISO.

On the final step of the install before rebooting the machine, I Alt+Ctrl+F1'd into a background TTY and added my USB drive into the VirtualBox instance. I mounted the USB volume to a directory and dd'd the whole virtual disk (/dev/sda, not /dev/sda1) to a new file on the USB drive.

Once complete, I unmounted the flash drive and ate it. (Note: Do not eat your flash drive.) I also unmounted it from VirtualBox, which returns it to the host operating system.

Finally, I returned to the GUI (Alt+Ctrl+F7) in the guest virtual machine and allowed the instance to reboot. (You don't have to do this, just power off the virtual machine and delete it.)

The next step was to make sure that the file I created on my USB drive was contiguous. Since I was using Windows to do this, I downloaded Contig.exe (http://technet.microsoft.com/en-us/sysinternals/bb897428.aspx) (part of the Microsoft SysInternals Suite) and ran it on the file to check if it was fragmented. (If you're not comfortable with the command line stuff, you can use WinContig (http://wincontig.mdtzone.it/en/) instead.) I also ran an analysis on the file again after it completed to make sure it was fully defragmented, several times of which it wasn't.

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Note: If you're host OS is Unix-type distro, you can use a Perl script called defragfs (http://sourceforge.net/projects/defragfs/) to do much the same thing.

Note II: For me, the file was still fragmented after running both of those utilities, so I used Contig.exe to create another file of the same byte size, which turned out to be a single fragment, and copied the contents of the old file over to the new one using dd and conv=notrunc as a parameter. You can also re-copy /dev/sda in the virtual machine to the new file using the same conv=notrunc. Then I deleted the old file.
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Once that completed, I simply set the following entry in the menu.lst file for Grub4DOS:



title Lubuntu 12.10 Persistent Install
find --set-root <image file path>
map --unsafe-boot <image file path> (hd0)
map --hook
chainloader (hd0)+1
rootnoverify (hd0)
root
And that was that! It worked! I tested it in an actual boot, and my computer exploded into persistent Lubuntu awesomeness! :D

Anywhoos, I hope my endeavors will help someone out there. I may even start an independent thread about this as a tutorial. This is a bit of a hack, really, so if there is a better way to do it, please let me know. (Or, better yet, pester Geza Kovacs (http://gkovacs.github.com/)—the maker of Lubi (http://lubi.sourceforge.net/)—to make a verson of Wubi/Lubi that can do this straight out of the box. :lol: )


Cheers!

–amanisdude
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P.S. I somehow managed to get two forums confused and inadvertently called you Paul in my last post, Fred. Sorry about that. :lol:
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[bcbc]

You can download a preinstalled compressed disk image (ubuntu, not lubuntu), and then replace ubuntu-desktop with lubuntu-desktop.

Here they are: http://releases.ubuntu.com/12.10/ubuntu-12.10-wubi-amd64.tar.xz
and http://releases.ubuntu.com/12.10/ubuntu-12.10-wubi-i386.tar.xz

I guess you just uncompress it and use resize2fs to get it to the size you want.