How do I create a bootable iso file from my current Ubuntu 20.04 machine?
Ubuntu Operating System Reinstaller
Hopefully the following should suit your requirements even though it does not involve an ISO file.
Procedure.
- Create a persistent USB using mkusb. Make the usbdata partition large enough to contain your operating system. See https://help.ubuntu.com/community/mkusb#Quick_start_manual_and_mkusb_PPA
Showing partitions created by mkusb persistent install.
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Boot the mkusb drive in the computer who's OS you want to backup.
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Open Gnome-Disks, (Disks), Select the disk you wish to backup on the left.
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Select the icon that looks like a stack of pancakes upper right.
- Click "Create Disk Image" and save the image to the usbdata partition of the persistent USB.
- When it comes time to restore your OS, boot the USB in the Target computer and use the pancake icon to restore the image to the hard drive. The restore will overwrite everything on the target drive. Best to test the image before deleting the original OS.