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Thread: Cannot make full/cold reboot.

  1. #1
    Join Date
    Aug 2013

    Cannot make full/cold reboot.

    I have a strange issue, whenever i try to restart my PC (either via GUI or CLI) I do not get a normal reboot (i.e. getting POST messages) but rather very quickly get dropped to the login screen.

    In fact I initially thought that Xorg was maybe crashing but I after I checked the logs it appears that a kernel actually boots (there are entries with 0.00 timestamps for example). Furthermore I booted the oldest available kernel (4.4.0-42) and upon restarting it restarted to the newest available kernel (4.4.0-91). I also got to see a message on screen, kexec: starting new kernel.

    This makes me thing that it probably is some kind of configurable behavior and not a bug.

    The system is Ubuntu 16.04.02 in an efi installation. There is a win 10 installation on another disk (it reboots to post normally). Fast/Secure boot etc are disabled in uefi settings.
    I don't have any issue in shutting down the machine or booting it.

    The hardware is Athlon 860k on Asus A88XM-PLUS. I have an amd rx480 using the amdgpu driver.

    And here are kernlog and syslog both start seconds before I tried to restart the machine (I emptied the logs).

    It is not a critical problem since I can just shutdown the machine but it makes me curious. Unfortunately I can't tell how long it has been like this.

    Any help is appreciated.

  2. #2
    Join Date
    Mar 2011
    19th Hole
    Ubuntu 18.04 Bionic Beaver

    Re: Cannot make full/cold reboot.

    The linux kernel has some arcane ACPI settings that may set your HW to skip the POST sequence in the event of a soft reboot (one that does not involve a power-down). Unfortunately, I do not know the ACPI call offhand. Some of my machines act the same way; others don't. I've always considered it a "feature", and since I feel that the POST routine only needs to be invoked once at power-up, I feel the time savings to be a convenience and therefore have never been bothered to delve into the guts of it.


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