Comment 23 for bug 1851123

@nio-wiklund, @mwhudson : Thanks for your replies.

@nio-wiklund : Your solution would probably do the trick, but has the inconvenient of indiscriminately replacing a string with another in the whole image, hence possibly in places where it's not desired.

I think I will rather do one of those two things :

1. Create a partition that occupies the remaining space on the USB stick, hence preventing the live image from creating (and writing to) one without my consent

2. Create a custom Grub config file on the EFI partition on the stick, specifying my own parameters

The first solution is the most straightforward, has the advantage the stick can be used for additional purposes, but the inconvenient that it's hardware-dependent (not all sticks have the same size). To have the integrity check work, I would have to rehash after modifying, and maintain different hashes, one hash per stick.

The second solution requires more changes, but would work for all sticks. It probably won't work if I boot the stick on a non-EFI BIOS though. For integrity-checking purposes I would have to rehash too, but would only require one hash for all sticks.

Concerning your change proposal, adding an additional entry to Grub solves indeed the problem of risking a typo compared to having to type "nopersistent" and/or "toram" at every boot, to avoid undesired writes. However, it still requires to never forget interrupting the boot process.

@mwhudson : Imho, the current situation of the 19.10 live image can be considered a bug, since it changes a default that has been there for more than a decade, and that's in many minds, that a live OS image is volatile.

That's not due to a coding error, like most bugs are, but rather in comparison to usually expected behaviour, or "untold specification".

Moreover, your reasons for wanting it to become a default are unclear, especially considering that the ones who want persistence could achieve that by passing a one-time option at boot, and being OK for subsequent boots, which obviously people who don't want persistence can't do, precisely because they don't want persistence.

For these reasons it can be worth clarifying, outside of a bug process why not. I just started a thread : https://ubuntuforums.org/showthread.php?t=2431843