What forces a reboot?

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I experience that my Ubuntu Linux requires a restart every now and then and also that it needs restart more often than in the old days (maybe it's because it updates more).



I understand that updating the kernel forces a reboot but is that a convenience and technically feasible to update without rebooting and only complicated?



Is it something that is technically impossible to update while the system is running?



"The system will go down for maintenance now...."



I understand that a BIOS update forces a reboot but I don't understand why it is absolutely necessary or if that is for convenience and making it much easier to update.



Reading a similar question, there were not convincing answers.



I believe that it is running binaries that should be replaced.










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  • 1




    What exactly are the problems you encounter that require you to reboot your pc to solve them?
    – saga
    Jan 15 '17 at 5:21










  • @saga I'll try and see. I add updates from Ubuntu where the updating asks me to install in the window manager, I press install and then I get the graphical prompt that I must reboot. It doesn't explicitly say what updates required the reboot.
    – Niklas Rosencrantz
    Jan 15 '17 at 14:12






  • 1




    Do you update using apt or software centre? If you use latter try upgrading with sudo apt-get update;sudo apt-get upgrade. It should work fine. Ubuntu store is not a very good tool you know.
    – saga
    Jan 16 '17 at 10:32














up vote
4
down vote

favorite












I experience that my Ubuntu Linux requires a restart every now and then and also that it needs restart more often than in the old days (maybe it's because it updates more).



I understand that updating the kernel forces a reboot but is that a convenience and technically feasible to update without rebooting and only complicated?



Is it something that is technically impossible to update while the system is running?



"The system will go down for maintenance now...."



I understand that a BIOS update forces a reboot but I don't understand why it is absolutely necessary or if that is for convenience and making it much easier to update.



Reading a similar question, there were not convincing answers.



I believe that it is running binaries that should be replaced.










share|improve this question



















  • 1




    What exactly are the problems you encounter that require you to reboot your pc to solve them?
    – saga
    Jan 15 '17 at 5:21










  • @saga I'll try and see. I add updates from Ubuntu where the updating asks me to install in the window manager, I press install and then I get the graphical prompt that I must reboot. It doesn't explicitly say what updates required the reboot.
    – Niklas Rosencrantz
    Jan 15 '17 at 14:12






  • 1




    Do you update using apt or software centre? If you use latter try upgrading with sudo apt-get update;sudo apt-get upgrade. It should work fine. Ubuntu store is not a very good tool you know.
    – saga
    Jan 16 '17 at 10:32












up vote
4
down vote

favorite









up vote
4
down vote

favorite











I experience that my Ubuntu Linux requires a restart every now and then and also that it needs restart more often than in the old days (maybe it's because it updates more).



I understand that updating the kernel forces a reboot but is that a convenience and technically feasible to update without rebooting and only complicated?



Is it something that is technically impossible to update while the system is running?



"The system will go down for maintenance now...."



I understand that a BIOS update forces a reboot but I don't understand why it is absolutely necessary or if that is for convenience and making it much easier to update.



Reading a similar question, there were not convincing answers.



I believe that it is running binaries that should be replaced.










share|improve this question















I experience that my Ubuntu Linux requires a restart every now and then and also that it needs restart more often than in the old days (maybe it's because it updates more).



I understand that updating the kernel forces a reboot but is that a convenience and technically feasible to update without rebooting and only complicated?



Is it something that is technically impossible to update while the system is running?



"The system will go down for maintenance now...."



I understand that a BIOS update forces a reboot but I don't understand why it is absolutely necessary or if that is for convenience and making it much easier to update.



Reading a similar question, there were not convincing answers.



I believe that it is running binaries that should be replaced.







upgrade reboot






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share|improve this question













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share|improve this question








edited Mar 20 '17 at 10:04









Community

1




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asked Jan 14 '17 at 22:48









Niklas Rosencrantz

1,02831437




1,02831437







  • 1




    What exactly are the problems you encounter that require you to reboot your pc to solve them?
    – saga
    Jan 15 '17 at 5:21










  • @saga I'll try and see. I add updates from Ubuntu where the updating asks me to install in the window manager, I press install and then I get the graphical prompt that I must reboot. It doesn't explicitly say what updates required the reboot.
    – Niklas Rosencrantz
    Jan 15 '17 at 14:12






  • 1




    Do you update using apt or software centre? If you use latter try upgrading with sudo apt-get update;sudo apt-get upgrade. It should work fine. Ubuntu store is not a very good tool you know.
    – saga
    Jan 16 '17 at 10:32












  • 1




    What exactly are the problems you encounter that require you to reboot your pc to solve them?
    – saga
    Jan 15 '17 at 5:21










  • @saga I'll try and see. I add updates from Ubuntu where the updating asks me to install in the window manager, I press install and then I get the graphical prompt that I must reboot. It doesn't explicitly say what updates required the reboot.
    – Niklas Rosencrantz
    Jan 15 '17 at 14:12






  • 1




    Do you update using apt or software centre? If you use latter try upgrading with sudo apt-get update;sudo apt-get upgrade. It should work fine. Ubuntu store is not a very good tool you know.
    – saga
    Jan 16 '17 at 10:32







1




1




What exactly are the problems you encounter that require you to reboot your pc to solve them?
– saga
Jan 15 '17 at 5:21




What exactly are the problems you encounter that require you to reboot your pc to solve them?
– saga
Jan 15 '17 at 5:21












@saga I'll try and see. I add updates from Ubuntu where the updating asks me to install in the window manager, I press install and then I get the graphical prompt that I must reboot. It doesn't explicitly say what updates required the reboot.
– Niklas Rosencrantz
Jan 15 '17 at 14:12




@saga I'll try and see. I add updates from Ubuntu where the updating asks me to install in the window manager, I press install and then I get the graphical prompt that I must reboot. It doesn't explicitly say what updates required the reboot.
– Niklas Rosencrantz
Jan 15 '17 at 14:12




1




1




Do you update using apt or software centre? If you use latter try upgrading with sudo apt-get update;sudo apt-get upgrade. It should work fine. Ubuntu store is not a very good tool you know.
– saga
Jan 16 '17 at 10:32




Do you update using apt or software centre? If you use latter try upgrading with sudo apt-get update;sudo apt-get upgrade. It should work fine. Ubuntu store is not a very good tool you know.
– saga
Jan 16 '17 at 10:32










2 Answers
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The only thing that absolutely requires a reboot is modifying the kernel. Any process can be killed if the program (or some library or other file that it depends on) has been upgraded, but that isn't the case for the kernel.



Actually, it's possible to patch a Linux kernel directly in memory sometimes. There are several tools that work at least in some cases: Ksplice, Kpatch, kGraft… Each of them works in some simple cases but not all; they typically work with security updates, as those don't change any internal interface (especially data structure formats), but not to upgrade between kernel versions. Ubuntu LTS supports kernel patching using livepatch since 16.04 with the 4.4 kernel with a proprietary client.



Although anything that isn't in the kernel can be upgraded on a running system, it still requires restarting the affected processes. On a server this means restarting the servers that use an executable, library, plugin, data file, configuration or other dependency that has been updated. On a desktop machine, this can mean getting users to log out and back in (e.g. if it's a bug in the graphics driver). Determining exactly what needs to be restarted can be difficult as it depends on the exact nature of the bug fix and how the program is used. Rather than go through the huge amount of work needed to determine this precisely, Ubuntu plays it safe and recommends a reboot in packages that think that restarting the service would be too fiddly. The way it works is that you get a prompt to reboot when a package's post-installation (post-upgrade, in this case) script declares that a reboot is required (see How can I tell what package requires a reboot of my system?).






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    up vote
    2
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    As far as I know you can still use the old system after upgrading, but generally will have to reboot to experience the upgraded system.

    As an exception, if I remember well, there is the KSplice technology which allows to apply security patches to a running kernel without having to reboot the system.






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      2 Answers
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      The only thing that absolutely requires a reboot is modifying the kernel. Any process can be killed if the program (or some library or other file that it depends on) has been upgraded, but that isn't the case for the kernel.



      Actually, it's possible to patch a Linux kernel directly in memory sometimes. There are several tools that work at least in some cases: Ksplice, Kpatch, kGraft… Each of them works in some simple cases but not all; they typically work with security updates, as those don't change any internal interface (especially data structure formats), but not to upgrade between kernel versions. Ubuntu LTS supports kernel patching using livepatch since 16.04 with the 4.4 kernel with a proprietary client.



      Although anything that isn't in the kernel can be upgraded on a running system, it still requires restarting the affected processes. On a server this means restarting the servers that use an executable, library, plugin, data file, configuration or other dependency that has been updated. On a desktop machine, this can mean getting users to log out and back in (e.g. if it's a bug in the graphics driver). Determining exactly what needs to be restarted can be difficult as it depends on the exact nature of the bug fix and how the program is used. Rather than go through the huge amount of work needed to determine this precisely, Ubuntu plays it safe and recommends a reboot in packages that think that restarting the service would be too fiddly. The way it works is that you get a prompt to reboot when a package's post-installation (post-upgrade, in this case) script declares that a reboot is required (see How can I tell what package requires a reboot of my system?).






      share|improve this answer


























        up vote
        4
        down vote



        accepted










        The only thing that absolutely requires a reboot is modifying the kernel. Any process can be killed if the program (or some library or other file that it depends on) has been upgraded, but that isn't the case for the kernel.



        Actually, it's possible to patch a Linux kernel directly in memory sometimes. There are several tools that work at least in some cases: Ksplice, Kpatch, kGraft… Each of them works in some simple cases but not all; they typically work with security updates, as those don't change any internal interface (especially data structure formats), but not to upgrade between kernel versions. Ubuntu LTS supports kernel patching using livepatch since 16.04 with the 4.4 kernel with a proprietary client.



        Although anything that isn't in the kernel can be upgraded on a running system, it still requires restarting the affected processes. On a server this means restarting the servers that use an executable, library, plugin, data file, configuration or other dependency that has been updated. On a desktop machine, this can mean getting users to log out and back in (e.g. if it's a bug in the graphics driver). Determining exactly what needs to be restarted can be difficult as it depends on the exact nature of the bug fix and how the program is used. Rather than go through the huge amount of work needed to determine this precisely, Ubuntu plays it safe and recommends a reboot in packages that think that restarting the service would be too fiddly. The way it works is that you get a prompt to reboot when a package's post-installation (post-upgrade, in this case) script declares that a reboot is required (see How can I tell what package requires a reboot of my system?).






        share|improve this answer
























          up vote
          4
          down vote



          accepted







          up vote
          4
          down vote



          accepted






          The only thing that absolutely requires a reboot is modifying the kernel. Any process can be killed if the program (or some library or other file that it depends on) has been upgraded, but that isn't the case for the kernel.



          Actually, it's possible to patch a Linux kernel directly in memory sometimes. There are several tools that work at least in some cases: Ksplice, Kpatch, kGraft… Each of them works in some simple cases but not all; they typically work with security updates, as those don't change any internal interface (especially data structure formats), but not to upgrade between kernel versions. Ubuntu LTS supports kernel patching using livepatch since 16.04 with the 4.4 kernel with a proprietary client.



          Although anything that isn't in the kernel can be upgraded on a running system, it still requires restarting the affected processes. On a server this means restarting the servers that use an executable, library, plugin, data file, configuration or other dependency that has been updated. On a desktop machine, this can mean getting users to log out and back in (e.g. if it's a bug in the graphics driver). Determining exactly what needs to be restarted can be difficult as it depends on the exact nature of the bug fix and how the program is used. Rather than go through the huge amount of work needed to determine this precisely, Ubuntu plays it safe and recommends a reboot in packages that think that restarting the service would be too fiddly. The way it works is that you get a prompt to reboot when a package's post-installation (post-upgrade, in this case) script declares that a reboot is required (see How can I tell what package requires a reboot of my system?).






          share|improve this answer














          The only thing that absolutely requires a reboot is modifying the kernel. Any process can be killed if the program (or some library or other file that it depends on) has been upgraded, but that isn't the case for the kernel.



          Actually, it's possible to patch a Linux kernel directly in memory sometimes. There are several tools that work at least in some cases: Ksplice, Kpatch, kGraft… Each of them works in some simple cases but not all; they typically work with security updates, as those don't change any internal interface (especially data structure formats), but not to upgrade between kernel versions. Ubuntu LTS supports kernel patching using livepatch since 16.04 with the 4.4 kernel with a proprietary client.



          Although anything that isn't in the kernel can be upgraded on a running system, it still requires restarting the affected processes. On a server this means restarting the servers that use an executable, library, plugin, data file, configuration or other dependency that has been updated. On a desktop machine, this can mean getting users to log out and back in (e.g. if it's a bug in the graphics driver). Determining exactly what needs to be restarted can be difficult as it depends on the exact nature of the bug fix and how the program is used. Rather than go through the huge amount of work needed to determine this precisely, Ubuntu plays it safe and recommends a reboot in packages that think that restarting the service would be too fiddly. The way it works is that you get a prompt to reboot when a package's post-installation (post-upgrade, in this case) script declares that a reboot is required (see How can I tell what package requires a reboot of my system?).







          share|improve this answer














          share|improve this answer



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          edited 23 hours ago









          Stephen Kitt

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          answered Jan 15 '17 at 23:49









          Gilles

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              up vote
              2
              down vote













              As far as I know you can still use the old system after upgrading, but generally will have to reboot to experience the upgraded system.

              As an exception, if I remember well, there is the KSplice technology which allows to apply security patches to a running kernel without having to reboot the system.






              share|improve this answer
























                up vote
                2
                down vote













                As far as I know you can still use the old system after upgrading, but generally will have to reboot to experience the upgraded system.

                As an exception, if I remember well, there is the KSplice technology which allows to apply security patches to a running kernel without having to reboot the system.






                share|improve this answer






















                  up vote
                  2
                  down vote










                  up vote
                  2
                  down vote









                  As far as I know you can still use the old system after upgrading, but generally will have to reboot to experience the upgraded system.

                  As an exception, if I remember well, there is the KSplice technology which allows to apply security patches to a running kernel without having to reboot the system.






                  share|improve this answer












                  As far as I know you can still use the old system after upgrading, but generally will have to reboot to experience the upgraded system.

                  As an exception, if I remember well, there is the KSplice technology which allows to apply security patches to a running kernel without having to reboot the system.







                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered Jan 15 '17 at 2:10









                  marc

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