Re: Kernel Update on Stretch
Hi, On 02/14/2017 12:58 AM, Daniel Bareiro wrote: > Some time ago I read that Linux 4.x incorporates the feature to be > updated without requiring a restart of the operating system. They incorporated parts of that. There are still some unsolved issues. See for example this article from last November about the topic: https://lwn.net/Articles/706327/ So there's no complete upstream support for this yet, there are several distributions that roll their own variants. > Since stretch incorporates a kernel of the 4.x series, this would imply > that we can update the kernel package and avoid reboots? No. There are two components to this: 1. The kernel must support loading live patches This is partially true for the kernel that will come with Stretch (CONFIG_LIVEPATCH=y), but (see the LWN article I linked) it doesn't actually work safely yet. 2. Someone needs to prepare the live patches. Currently nobody in Debian is doing that. You could do it yourself with the right tooling (look at kpatch and kgraft), but preparing these kinds of patches is very complicated. (And that still doesn't solve the problem that the current patch loading support is unsafe, see 1.) Further reading: https://lists.debian.org/1460472961.25201.200.ca...@decadent.org.uk Depending on whether there is movement in the upstream kernel there is a chance this might be a thing in Buster, but it definitely won't work out of the box in Stretch. You'll still need to reboot. Regards, Christian
Re: Kernel Update on Stretch
Hi, Sven. On 14/02/17 10:19, Sven Hartge wrote: > He thinks of mechanisms like ksplice or kpatch where you can > alter/patch the running kernel without rebooting the system. Yes, I had read some about this and that, for example, Ubuntu has it available but as a paid service that one can hire. What is not clear to me is if these systems are complemented with the package system or it is something independent. I think it's some kind of hot patching, which would not require installing a new version of the kernel package. Thanks for your reply. Kind regards, Daniel signature.asc Description: OpenPGP digital signature
Re: Kernel Update on Stretch
Hi, Darac. On 14/02/17 10:01, Darac Marjal wrote: >>> Some time ago I read that Linux 4.x incorporates the feature to be >>> updated without requiring a restart of the operating system. >> Some Linux Distributions have such a feature. Debian is not one of them. > Actually, yes it is, you just need to install the user space tools.[1] > > The facility is called "kexec" (named after the system call to 'EXECute > a new Kernel', I suspect). Install the "kexec-tools" package and, if I'm > reading that page correctly, the "reboot" command will be replaced by a > kexec call (see the linked page, though, for precautions about your > first reboot). > > [1] wiki.debian.org/BootProcessSpeedup#Using_kexec_for_warm_reboots Reading about the documentation you mentioned and researching a little more about kexec, I see that kexec skips the BIOS init part, but it requires a boot anyway. In fact, I see that kexec is present in Jessie and I've also seen some examples of use with 2.6 series kernels. I understand that what I mentioned was introduced with Linux 4.x. Thanks for your reply. Kind regards, Daniel signature.asc Description: OpenPGP digital signature
Re: Kernel Update on Stretch
Darac Marjalwrote: > On Tue, Feb 14, 2017 at 01:46:08PM +0100, Sven Hartge wrote: >> Daniel Bareiro wrote: >>> Some time ago I read that Linux 4.x incorporates the feature to be >>> updated without requiring a restart of the operating system. >> Some Linux Distributions have such a feature. Debian is not one of >> them. > Actually, yes it is, you just need to install the user space tools.[1] You misunderstood Daniel. He thinks of mechanisms like ksplice or kpatch where you can alter/patch the running kernel without rebooting the system. > The facility is called "kexec" (named after the system call to > 'EXECute a new Kernel', I suspect). Install the "kexec-tools" package > and, if I'm reading that page correctly, the "reboot" command will be > replaced by a kexec call (see the linked page, though, for precautions > about your first reboot). kexec still "reboots" the system, meaning the complete userland has to be stopped before the new kernel can be started. You only gain time because you don't have to wait for the UEFI/BIOS, RAID cards, network cards, etc. to initialize. Grüße, Sven. -- Sigmentation fault. Core dumped.
Re: Kernel Update on Stretch
On Tue, Feb 14, 2017 at 01:46:08PM +0100, Sven Hartge wrote: Daniel Bareirowrote: Some time ago I read that Linux 4.x incorporates the feature to be updated without requiring a restart of the operating system. Some Linux Distributions have such a feature. Debian is not one of them. Actually, yes it is, you just need to install the user space tools.[1] The facility is called "kexec" (named after the system call to 'EXECute a new Kernel', I suspect). Install the "kexec-tools" package and, if I'm reading that page correctly, the "reboot" command will be replaced by a kexec call (see the linked page, though, for precautions about your first reboot). [1] wiki.debian.org/BootProcessSpeedup#Using_kexec_for_warm_reboots Grüße, Sven. -- Sigmentation fault. Core dumped. -- For more information, please reread.
Re: Kernel Update on Stretch
Daniel Bareirowrote: > Some time ago I read that Linux 4.x incorporates the feature to be > updated without requiring a restart of the operating system. Some Linux Distributions have such a feature. Debian is not one of them. Grüße, Sven. -- Sigmentation fault. Core dumped.
Kernel Update on Stretch
Hi all! Some time ago I read that Linux 4.x incorporates the feature to be updated without requiring a restart of the operating system. Since stretch incorporates a kernel of the 4.x series, this would imply that we can update the kernel package and avoid reboots? Thanks in advance. Kind regards, Daniel signature.asc Description: OpenPGP digital signature