Before you begin, I'm assuming the package flag +symlink is enabled for kernel packages.  Just after download of the package, this just automatically creates /usr/src/linux, which is a direct symlink to /usr/src/linux-X.XX.XX-gentoo, which is whatever directly has the actual source.

Also, read through the entire thing.

To make copy-paste really easy, you should use text search and replace to change the commands below.  For example, if the new version is 5.11.6 and the existing installed version is 5.11.5:

First, search for every instance of "5.11.5" and replace it with "5.11.6".

Second, find and replace every instance of "5.11.4" to "5.11.5".  The order is important, or the wrong text might get replaced.

I also prefer to run all these commands within tmux, though you don't have to of course.  The process is also sloppy in places, and can stand to be refined and improved.



1. Obviously, the latest stable kernel is never marked as an official stable in Gentoo, which means you have to use package.use to unmask the package and make it available for download, releasing the failsafe.

Depending on whether you use a single package.use file, or a package.use directory with files within that have the same name as the package, you'd use one of the following:

1a.
sed -i s/gentoo-sources-5.11.9/gentoo-sources-5.11.10/ /etc/portage/package.accept_keywords && cat /etc/portage/package.accept_keywords

1b.
sed -i s/gentoo-sources-5.11.9/gentoo-sources-5.11.10/ /etc/portage/package.accept_keywords/gentoo-sources && cat /etc/portage/package.accept_keywords/gentoo-sources

Note: The "cat" command at the end isn't technically needed, but I like to see if the file was edited correctly.  Sometimes it might not be, if the version name includes a suffix like -r1, but it usually doesn't.


2. You have to update the local indexes.  This doesn't depend on step 1, so you could run this command while performing step 1.

2.
emerge --sync && eix-update


3. Now you have to download the package.

Dependencies: Steps 1 and 2.

3.
emerge =sys-kernel/gentoo-sources-5.11.10 && emerge -NuD @world

Note: Why the extra bit at the end to update everything?  Other than being a good idea in general, occasionally there's a GCC update, though not usually.  Might as well compile the kernel with the latest GCC too.


4. Now to configure the kernel.  What this does, is copy the previous existing configuration to the new source directly.  But you must save the configuration again, since there might be new options.  The defaults are likely fine, but the options need to be saved.  Though if you want or need to change the options, edit as needed.

Dependencies: Steps 1, 2, and 3.

4.
cd /usr/src && cp linux-5.11.9-gentoo/.config linux/

cd linux/ && make menuconfig


5. Now obviously, you have to compile the kernel.  This series of commands performs the following tasks.  It compiles the kernel and modules, removes the old files from the /boot directory, installs the modules, installs the kernel, creates the initramfs, and creates a new grub configuration file.  By removing the previous kernel version files in /boot, you keep the list clean.

The riskiest period is when the initramfs is being created, but the new grub configuration file hasn't been made yet, so the existing file will reference a kernel that doesn't exist at that moment in time.

Dependencies: Steps 1, 2, 3, and 4.

Use 5a for single core VPS, or 5b for a PC/server with lots of cores.  The only difference is the -j argument.  The whole thing is there just to make it easy to copy-paste.

5a.
make -j1 && rm /boot/*5.11.9* && make modules_install && make install && genkernel --install initramfs && grub-mkconfig -o /boot/grub/grub.cfg

5b.
make -j16 && rm /boot/*5.11.9* && make modules_install && make install && genkernel --install initramfs  && grub-mkconfig -o /boot/grub/grub.cfg


6. You'd want to clean up the old kernel packages too.  You can easily run this while the kernel is compiling.  In the event of a power failure, the previous kernel should still be available to boot.

Dependencies: Steps 1, 2, 3, and 4.

6.
emerge -cv =sys-kernel/gentoo-sources-5.11.9 && rm -rf /usr/src/linux-5.11.9-gentoo/ && emerge --depclean && eclean-dist --deep


7. Reboot the system to make the new kernel take effect.  Step 6 isn't required for this, but is a good idea anyway to clean it up.

Dependencies: Steps 1, 2, 3, 4, and 5.

7.
reboot && exit


8. Make sure the new kernel is installed.

Dependencies: 1, 2, 3, 4, 5, and 7.

8.
cat /proc/version