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Compiling and installing the Gentoo Linux kernel on emerge without genkernel (part 1)

Posted by Daniel Lange on
Gentoo

Gentoo emerges of sys-kernel/gentoo-sources will nicely install the current kernel into /usr/src/linux-* but it will not compile them.

The Gentoo wiki kernel documentation has a script snippet to automate the kernel build with genkernel.

I do not like to use genkernel as it brings in lots of firmware files to build initrds that are not needed on virtual hardware. It also makes building the kernel slower.

So, the plain approach:

Make emerge sys-kernel/gentoo-sources symlink the latest kernel to /usr/src/linux so we can find it easily:

echo "sys-kernel/gentoo-sources symlink" >> /etc/portage/package.use/gentoo-sources

Create /etc/portage/env/sys-kernel/gentoo-sources with the following:

post_pkg_postinst() {
        CURRENT_KV=$(uname -r)
        unset ARCH
        if [[ -f "${EROOT:-/}usr/src/linux-${CURRENT_KV}/.config" ]] ; then
                cp -n "${EROOT:-/}usr/src/linux-${CURRENT_KV}/.config" "${EROOT:-/}usr/src/linux/.config"
                cd "${EROOT:-/}usr/src/linux/" && \
                make olddefconfig && \
                make -j5 && make modules_install && make install && \
                grub-mkconfig -o /boot/grub/grub.cfg
        fi
}

This will compile the next kernel on the basis of the config of the currently running kernel, install the modules and the kernel bzImage and update grub so it knows about the new kernel for the next reboot.

If you forget to unset ARCH the Linux build system will complain like:

Makefile:583: arch/amd64/Makefile: No such file or directory
make: *** No rule to make target 'arch/amd64/Makefile'.  Stop.

You can test the new magic by re-emerging the latest kernel, e.g. currently emerge =sys-kernel/gentoo-sources-5.4.80-r1:

Installing System Rescue (CD) to a flash drive

Posted by Daniel Lange on
Linux

System Rescue, the project formerly known as System Rescue CD, has moved from being based on Gentoo to being built on Arch Linux packages.

With this their ISO layout changed substantially so when updating my trusty recue USB flash drive, I could not just update the kernel, initrd and the root filesystem image as I had typically done every other year before.

The "Installing on a USB memory stick" documentation is good for Windows (use Rufus, it's nice) but rather useless for Linux. They recommend a dd or the fancy graphical version of that, called usbimager.

I much prefer to have a flash drive that I can write to over an image of a CD (ISO) written 1:1 onto the flash media.

The basic idea is to use the bulk of the System Rescue ISO contents but amend these with your own grub and syslinux so they work as intended over the supplied ones that are bound to the ISO layout a bit too much.

I did this on Debian Buster but with some adjustments to paths and what packages to install, any recent Linux distribution should do:

Continue reading "Installing System Rescue (CD) to a flash drive"