[all variants] Unattended-upgrades can break persistent live media

Looking at the persistent live Ubuntu 16.04 LTS system - the Software & Updates screen / Update - I notice, that Automatic updates is set to 'Download and install automatically'. This is bad in a persistent live system.

After leaving the persistent live Ubuntu 16.04 LTS system running overnight, I found that it had performed an automatic upgrade:

df revealed that the content in casper-rw had increased to 1.6 GiB.

This is risky: If not enough space (and inodes) in the casper-rw partition or file, the upgrade operation will be incomplete and fail. There might be big problems even if there is space left in casper-rw, and finally, this is wasting the available space, unless you have a huge casper-rw partition.

I am surprised that the persistent live system started an automatic security upgrade. I don't think it is caused by the installer (mkusb), because the files controlling those actions are not touched. I can test what happens in an Ubuntu 16.04.1 LTS system, that I leave by itself for a long time.

Until this is resolved, it is a good idea to disable unattended-upgrades, but above all, to take regular backups, when you use a persistent live system.

Is this a bug?

Should I write a bug report about it? In that case against which package?

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See the following links for more details,

Unattended-upgrades broke persistent live media

reply with output from df

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