I have found that when I click the shutdown button when logged into a normal user account that once it has terminated all running processes and it says something about a modem shutting down, it can take up to 10-15 minutes or more to halt.

But when in the console running the command:

sudo poweroff

That it then does shutdown almost instantaneously. This then seems to be because as a normal user, I do not have the privileges to terminate a process which is then stopping the machine from shutting down.

This was not always the case, so is there any way around this?

I am running Ubuntu 14.10.


It didn't work for me.

Instead of

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=off"

I used

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force"

and it works. :-)

  • I changed the formatting. I hope this is ok for you. – A.B. May 15 '15 at 15:17

A couple of things to try:

  1. Add a line to the following file: /etc/default/grub
    when you open the line will most likely read:


    change this line to be:

    GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=off"

    when you're all done you need to update grub for the change to take effect

    sudo grub-update

    I believe the first shutdown after these changes will have the same issues, but moving forward should be resolved.

  2. Blacklist DMA this will default to use PIO instead. Differences found here:

    details - do the above by going to


    with your text editor and appending these line of text:

    blacklist dw_dmac
    blacklist dw_dmac_core

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