Convert Ubuntu Core image to bootable ISO

Question

A VPS provider offers its users the ability to install and run any distribution, provided that you upload a bootable ISO image.

I'd like to run Ubuntu Core, however I haven't found a way to convert the images that Canonical provides to a bootable ISO.

qemu-img reports that the image is in raw format:

[chb]$ qemu-img info ubuntu-core-18-amd64.img
image: ubuntu-core-18-amd64.img
file format: raw
virtual size: 3.6G (3879731200 bytes)
disk size: 302M

I can use VirtualBox's VBoxManage tool to convert this "raw" image to a virtual disk that VirtualBox will recognize and boot:

VBoxManage convertfromraw ubuntu-core-18-amd64.img --format VDI \ 
    ubuntu-core-18-amd64.vdi

I've looked at iat but it seems focused on converting various flavors of optical disc images to one another. I thought raw2iso might do the trick...

raw2iso MODE1 < ubuntu-core-18-amd64.img > ubuntu-core-18-amd64.iso

...but, even though the byte size of the img file is a multiple of 2048, the output isn't recognized by anything.

Here's what hdiutil imageinfo says about the img file:

Size Information:
    Total Bytes: 3879731200
    Compressed Ratio: 1
    Sector Count: 7577600
    Total Non-Empty Bytes: 3879731200
    Compressed Bytes: 3879731200
    Total Empty Bytes: 0
    ...
partitions:
    partition-scheme: GUID
    block-size: 512
    partitions:
            0:
                    partition-name: Protective Master Boot Record
                    partition-start: 0
                    partition-synthesized: true
                    partition-length: 1
                    partition-hint: MBR
            1:
                    partition-name: GPT Header
                    partition-start: 1
                    partition-synthesized: true
                    partition-length: 1
                    partition-hint: Primary GPT Header
            2:
                    partition-name: GPT Partition Data
                    partition-start: 2
                    partition-synthesized: true
                    partition-length: 32
                    partition-hint: Primary GPT Table
            3:
                    partition-name:
                    partition-start: 34
                    partition-synthesized: true
                    partition-length: 2014
                    partition-hint: Apple_Free
            4:
                    partition-UUID: E765AD58-B838-4A24-8C2A-E022D7BEF1E5
                    partition-name: BIOS Boot
                    partition-hint-UUID: 21686148-6449-6E6F-744E-656564454649
                    partition-start: 2048
                    partition-number: 1
                    partition-length: 2048
                    partition-hint: 21686148-6449-6E6F-744E-656564454649
            5:
                    partition-UUID: CC8F1CE4-0C99-4ECC-A757-FBC3FF6B9B71
                    partition-name: EFI System
                    partition-hint-UUID: C12A7328-F81F-11D2-BA4B-00A0C93EC93B
                    partition-start: 4096
                    partition-number: 2
                    partition-length: 102400

How can I convert this file to something that is recognized by most systems as a bootable, iso9660 image?

Answer 1

It can't be turned into a bootable iso without some major work. The reason is that it isn't an installation disk so much as an installation hard drive image. Possibly due to limitations of the iso format?

The suggestion is to 'burn' it onto a USB or SD Card, or as you've found, a virtual hard drive.

For me, I converted it to a .vmdk using VBoxManager so I could use it in VMWare ESXi

VBoxManage convertfromraw ubuntu-core-18-amd64.img ubuntu-core-18-amd64.vmdk --format=VMDK

The other options include VDI (VirtualBox) and VHD (Microsoft Virtual PC).

Depending on where you're trying to set up Ubuntu Core the rest of the instructions change, but it's essentially booting off the hard drive/usb/sd and installing it as per usual.