I'm using CUBIC to create a custom Ubuntu ISO. I have downloaded ubuntu-16.04.3-server-amd64.iso as a base image, and specified ~/cubicworkspace as my working folder. But when I click "Next" and it is supposed to bring me into the chroot-ed environment, I get:

WARNING! You are NOT in the chroot environment. Exiting.

The host system is a fresh install of Ubuntu 16.04 desktop. I confirmed squashfs-tools are installed. I can't find useful/relevant docs anywhere. Help? :)

I tried following some manual creation steps here to the point where I ran unsquashfs and mounted a few system directories in the chroot, and then when I moved the "unsquashed FS" into the folder in my CUBIC workspace, I run cubic again, I do get:

You are in the chroot environment.

And I can do some customizations, but then when I click Next, CUBIC says "You have exited from the terminal. Click the Back button to re-enter the chroot terminal." and the Next button is grayed out. :(

How do I fix this so that CUBIC just works? Apparently my little hack doesn't work to the point where I can actually make the image. And the wiki I linked to seems really outdated...

  • Try to execute at terminal session: sudo cubic
    – Redbob
    Sep 8 '17 at 16:29
  • @Redbob "Cubic may not be run as a privileged user."
    – Matt
    Sep 8 '17 at 16:54
  • Did you see that? askubuntu.com/questions/741753/…
    – Redbob
    Sep 8 '17 at 16:57
  • @Redbob Yes, I even linked to that page in my question.
    – Matt
    Sep 8 '17 at 17:08

I found your question trying to solve the same problem. Since I couldn't find an answer, here is how I eventually solved it:

Cubic logs to stdout, which in my case was ~/.cache/lxsession/Lubuntu/run.log.

Cubic expands the iso, then unsquashes the filesystem in the casper/ folder. I found that the Ubuntu Server 16.04 ISO did not have a casper/ folder, but the squashed filesystem was in install/.

I fixed it by running sudo sed -i 's/casper/install/g' /usr/share/cubic/utilities.py. NOTE: This modifies the Cubic code and is NOT reversible in the same way -- it'd be easiest to uninstall then reinstall it.

Apparently there is also a bug report about Cubic not supporting Ubuntu Server: https://bugs.launchpad.net/cubic/+bug/1743177



Found this because I had the same issue, on my side I just deleted the project and restarted without changing the suggested iso name and it worked.

using 18.04 recent release of Cubic on clean minimal install

  • Most likely, the squash file system was not extracted fully (i.e. all the files under the root "/" directory could not be extracted from the original iso). When you deleted the project, the squash files system was extracted again, successfully.
    – Enterprise
    Jun 10 '20 at 2:59

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