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David Balažic
Asked: 2018-07-09 02:59:50 +0800 CST

How to prevent Live CD from changing hardware clock

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The Live environment sets and writes the time in UTC to the hardware ("BIOS") clock. Which of course borks it for Windows. (see Ubuntu bug 1703479)

Is there a boot option or similar to make it not do that?

Either:

  • set it so use localtime in HW clock, or
  • set it to never write to the HW clock (after all a live CD should not make changes to the system, at least not automatically)
  • maybe some other solution

PS: The mentioned bug was reported for version 17.04, while it happened to me with 18.04 (ubuntu-18.04-desktop-amd64.iso).

clock live-environment

1 Answers

  1. Is there a boot option or similar to make it not do that?

    No.

    set it to never write to the HW clock (after all a live CD should not make changes to the system, at least not automatically)

    This should be the case. A live session never ever ever should make permanent changes to a system. It defeats the purpose of a live session. But this has been the case for a long time now so I expect Linux maintainers to have another idea about this. Using localtime is too limited anyway.

    The live session is likely to run the following command 

    hwclock --systohc

    and it will do this every time you start from the live session. If not that /etc/default/rcS will likely have UTC=yes as a parameter.

    To prevent this from happening you would need to create your own live session ISO without adding either of these 2 settings.

    The easier fix would be to tell Windows to use UTC instead of localtime. See for instance howtogeek's method on how to do that. It is stupid to use localtime anyways as this does not support other operating systems than the one you are using.

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