Upgrading the Slackware Kernel Safely

Date: April 2, 2026

This page is my running guide and notes for upgrading the kernel on Slackware while keeping a known working boot option available.

What this guide covers

Downloading the kernel source
Preparing the existing config
Building the kernel and modules
Copying files into /boot
Creating an initrd if needed
Updating GRUB
Verifying the boot
Troubleshooting common problems

Before starting

Before doing anything, make sure you still have a known good kernel entry in GRUB. Do not remove your old working kernel until the new kernel has booted successfully.

Keep a backup boot option
Make sure /boot has enough space
Know whether your system needs an initrd
Double-check your current kernel version before starting

Check current kernel

uname -r

This shows the kernel you are currently running.

Go to the kernel source directory

cd /usr/src/linux

Make sure this points to the source tree you actually want to build.

Use your current config

cp /boot/config-$(uname -r) .config
make olddefconfig

This uses your current kernel config as the base and updates it for the new source tree.

Build the kernel

make -j8
make modules_install

Adjust the -j8 value to match your system.

Copy kernel files into /boot

cp arch/x86/boot/bzImage /boot/vmlinuz-custom
cp System.map /boot/System.map-custom
cp .config /boot/config-custom

I prefer using unique names so I do not overwrite my known working files.

Create initrd if needed

mkinitrd_command_generator.sh -k 6.x.x

Use the output of the generator and create the initrd for the exact kernel version you built.

Update GRUB

grub-mkconfig -o /boot/grub/grub.cfg

After this, verify that the new kernel appears in the GRUB menu while the old one is still present.

Reboot and verify

Reboot into the new kernel, then confirm the system is running what you expected.

uname -r

Things I watch for after boot

NVIDIA driver loads correctly
Network comes up normally
Audio works
Suspend and resume still work
No missing modules
Temperatures and fan control are normal

Troubleshooting

Kernel boots but modules are missing

Make sure make modules_install completed successfully and that you booted the kernel that matches the installed modules.

System does not boot

Boot the older known working kernel from GRUB and review the kernel, initrd, and GRUB entries.

NVIDIA driver breaks

Rebuild or reinstall the NVIDIA driver for the new kernel if needed.

Wrong initrd

Regenerate the initrd for the exact kernel version you installed.

My notes

Add your own real-world notes here, such as:

How long the build took
What command you used for make
Whether you used olddefconfig
Any NVIDIA issues
Any GRUB mistakes you ran into
How you verified success

Final thoughts

The safest approach is to treat kernel upgrades as reversible. Keep the old kernel, label files clearly, and confirm the new install works before cleaning anything up.

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