Best way to update kernel?

raddaqii · Posted: Sat Jul 23, 2016 8:24 am Post subject: Best way to update kernel?

Just to get things in order.. to upgrade the kernel I usually do the following on my home machine:

* emerge whatever new version comes with a portage sync, e.g. emerge =sys-kernel/gentoo-sources-4.6.2
* eselect kernel list
* eselect kernel set <number of new version>
* cd /usr/src/linux && cp ../linux-<previous-version>/.config .oldconfig
* make oldconfig <- keep enter pressed to answer all questions with the default if no hardware has changed
* make menuconfig <- optional, if I need features I hadn't enabled before
* make && make modules_prepare && make modules && make modules_install && make install <- this I keep in a bash-oneliner in /usr/local/bin/make-oneliner
* copy and update given line like modules_4_4_1_gentoo="vboxdrv vboxnetflt vboxnetadp vboxvideo" in etc/conf.d/modules
* grub2-mkconfig <- now this command fails as in "runs, but does not generate a grub2 entry for the most recent kernel", I so manually enter stuff into /boot/grub/grub.conf
* from time to time (usually when /boot runs full) I do eclean-kernel -n 4 or somesuch
* reboot

Now that seems inefficient, and it might be about time I update that process I've been following the last decade or so.

What are your suggestions? Since there hardly is a canonical way, how do you upgrade your kernel?
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raddaqii · Posted: Sat Jul 23, 2016 8:37 am Post subject:

So I just found a range of useful options in /usr/src/linux/'s make help:

The Doctor · Moderator Joined: 27 Jul 2010 Posts: 2678

The only real problem I see is accepting all the defaults. 99% of those are just adding worthless bloat since most new hardware options will default to "Yes" which is clearly not what you want and most of the other new stuff is similarly useless.
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Cyker · Veteran Joined: 15 Jun 2006 Posts: 1746

Mine is vaguely something like
emerge new kernel
make mrproper
copy /usr/src/linux/.config /usr/src/<newkernel>
eselect kernel <newkernel>
make oldconfig
make menuconfig
mount /boot
make
make firmware_install
make modules_install
make install
grub2-mkconfig > /boot/grub/grub.cfg
umount /boot

jonathan183 · Guru Joined: 13 Dec 2011 Posts: 318

Hu · Moderator Joined: 06 Mar 2007 Posts: 21593

I like make oldnoconfig instead of make oldconfig. It automatically answers No to every new question, while reusing answers to any questions that match the existing configuration. It saves me from holding down enter. As The Doctor hints, most new choices should be answered No unless you know you need them.

[Edit: as pointed out below, make oldnoconfig is documented to work differently from how I thought it did based on its name. I take comfort in knowing that many other people trusted that it did what its name said it did.]

jonathan183 · Guru Joined: 13 Dec 2011 Posts: 318

Ant P. · Watchman Joined: 18 Apr 2009 Posts: 6920

raddaqii · Posted: Mon Jul 25, 2016 4:03 pm Post subject:

A fine plethora of how to do it! :D

Apparently jonathan183 figured it out, oldnoconfig produces the same output as olddefconfig.

sheep204 · n00b Joined: 28 Dec 2005 Posts: 31

github has some solutions.But I never use it. I like the feeling of press keyborad when upgrade gentoo system.
https://github.com/hwoarang/gentoo-scripts/blob/master/kernel/update-kernel.sh
https://github.com/sakaki-/genup

mv · Watchman Joined: 20 Apr 2005 Posts: 6747

If you have a separate KBUILD_OUTPUT (which I recommend anyway for security reasons: You don't want to compile your kernel with root permissions :wink:

) and you don't change it between kernels, there is no need to copy any .config. You can then also use the sys-kernel/kernel script from the mv overlay. It does not deal with initrds yet, since there was no need for it so far.
In order to check for changes in the configuration, usually I save the new configuration after "make nconfig" and then use kccmp. After this, I read what some new options mean (and perhaps check why some options have changed "automagically"); quite often, I deactivate some of the new which have a "yes"/"modules", though not always...

Tony0945 · Posted: Tue Aug 23, 2016 1:31 pm Post subject:

raddaqii · Posted: Mon Sep 05, 2016 10:04 am Post subject:

+1 for not having to wonder where you placed that last kernel's .config, and +1 for the built-in reminder to update that boot config.

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Gentoo from 2004.3

Oh, took a new home in the fediverse: find me in the stream on pluspora.com: https://pluspora.com/tags/gentoo

proteusx · Guru Joined: 21 Jan 2008 Posts: 338

This is how I update my kernel for many years.

Syl20 · l33t Joined: 04 Aug 2005 Posts: 619 Location: France

You can add "make install", to avoid setting symlinks to /usr/src (if /boot and/or /usr are on distinct FS, your method doesn't work).
If you added some symlinks to the current kernel, they are updated, so you don't need to modify your grub config :

proteusx · Guru Joined: 21 Jan 2008 Posts: 338

Roman_Gruber · Posted: Tue Sep 06, 2016 3:01 pm Post subject:

well to speed up things, written down without verificatin, please check manpage of man

raddaqii · Posted: Wed May 09, 2018 10:15 am Post subject:

FWIW, while still having machines around where I handle kernel configs explicitly, on recent builds I feel I have levelled up following Sakakis EFI Install Guide and grown to like having parts of all this managed by tools like genup, buildkernel. It is considerable less hassle, and I get to call buildkernel --menuconfig if I need to.
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Gentoo from 2004.3

Oh, took a new home in the fediverse: find me in the stream on pluspora.com: https://pluspora.com/tags/gentoo

ericbish · n00b Joined: 27 Apr 2018 Posts: 29

Well, if you are looking for "easiest", it's pretty hard to beat:

cd /etc/kernels

cp <current-kernel-config> <new-kernel-config>

cd /usr/src/

rm linux && ln -s <new-kernel> linux (this can also be automated if you so choose)

genkernel all (or if you use lvm: genkernel --lvm all, or if you want to edit the kernel config add a --menuconfig, or xconfig, or whatever you like here as well, lots of options for this line)

grub-mkconfig -o /boot/grub/grub.cfg (for most systems, if you use efi or something, hit the grub wiki)

lots of other ways to do it, but the above is pretty easy

Every once in a blue moon, you might have an issue with something not correctly supported between kernel configs, or need to modify due to new options......but I'll say that updating to new kernels by copying my old /etc/kernels config to the new kernel has worked without issue for many many years.

The Main Man · Posted: Wed May 09, 2018 11:32 pm Post subject:

I'm using 'make olddefconfig' , always figured that it can't be just new hardware that's new in that new kernel (options wise), there are probably some other options in there and if it was intended for some option to be set then that 'olddefconfig' would do that, yeah new hardware would also be added but I can go through that once in a while and deselect those. I never went through looking at all new items and answering Y or N to each, so I'm not sure if the bulk of it is just new hardware.