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I have cloned from the Ubuntu family iso files to USB pendrives, and the result has been live (live-only) drives, where nothing can be saved past shutdown and reboot.

But an Ubuntu 19.10 live drive cloned from the iso file creates and writes to a casper-rw partition. It seems to be a new feature.

  • How can this happen and how can I avoid that and get a live-only drive?
sudodus
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1 Answers1

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Cloned drive

A cloned drive, created with the 'Startup Disk Creator' in Ubuntu 16.04 LTS or newer versions, has a hybrid iso9660 file system, which works both in DVDs and USB pendrives (and memory cards), but it is read-only by design, so you cannot edit anything in it. Also 'Disks' alias gnome-disks, and 'mkusb' (when cloning and creating live-only drives) make USB drives with a hybrid iso9660 file system.

But a cloned Ubuntu 19.10+ live drive is not really live-only

Isn't live the default for a cloned drive?

Well, it used to be, and it is still live but not live-only in 19.10.

The default action is that a casper-rw partition is created automatically and it is mounted to /var/crash and /var/log, so that some of the things you are doing are logged.

  • This is good for debugging for example when there are problems during the installation of Ubuntu into an internal drive,
  • but you may want to use a live-only drive for payments and other tasks where you want highest possible security and privacy.

How to make your USB boot drive with Ubuntu 19.10+

  • There is a new feature in the casper package in Ubuntu 19.10. It makes it much easier to create and use a casper-rw partition for persistence, in other words to make a persistent live drive.

  • This feature is also used to create logs for debugging when the drive is running live (without the boot option persistent).

  • You can edit your binary iso file and replace the cosmetic boot options quiet splash with the boot option 'persistent ' or 'nopersistent' (the strings contain 12 characters, so the replacement can be done without any offset in the following part(s) of the iso file. You can do it with sed

    sed 's/quiet splash/persistent  /' standard.iso > persistent.iso
sed 's/quiet splash/nopersistent/' standard.iso > nopersistent.iso

    and clone the modified iso file, or flash directly with

    sed 's/quiet splash/persistent  /' standard.iso > /dev/sdx
sed 's/quiet splash/nopersistent/' standard.iso > /dev/sdx

    where x is the device letter for the USB pendrive.

You can do it with a safety belt using mkusb-plug

Here we focus on 'No-persistent live drive' in order to make a purely live-only drive, where nothing will be preserved after shutdown and reboot.

sudodus
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