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NewKernel.md

Compiling Linux Kernel 6.18 on Slackware Linux 15 (x86_64)

Prerequisites

Before starting, ensure you have the necessary build tools installed. Slackware 15 includes most of these by default if you did a full installation. Verify the following are present:

  • gcc and g++
  • make
  • bc
  • flex
  • bison
  • libelf (part of the elfutils package)
  • openssl and openssl-devel headers
  • perl
  • ncurses-devel (only needed if you plan to run menuconfig later)

Check for a package with pkgtool or simply try the build — missing tools will cause the build to fail with clear error messages.

Step 1: Download the Kernel Source

Go to https://www.kernel.org and find the latest 6.18.x stable release. Download both the tarball and its PGP signature:

cd /usr/src
wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.18.tar.xz
wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.18.tar.sign

Note: Replace 6.18 with the latest point release (e.g., 6.18.3) as shown on kernel.org.

Step 2: Verify the Signature (Recommended)

The tarball on kernel.org is compressed; the .sign file covers the uncompressed tarball. Decompress first, then verify:

unxz linux-6.18.tar.xz
gpg --verify linux-6.18.tar.sign linux-6.18.tar

If GPG reports a missing key, fetch it:

gpg --keyserver hkps://keyserver.ubuntu.com --recv-keys <KEY_ID>

The key ID will be shown in the GPG output. Trusted kernel signing keys belong to Linus Torvalds and Greg Kroah-Hartman.

Step 3: Extract the Source

tar xf linux-6.18.tar
cd linux-6.18

Step 4: Copy Your Current Kernel Configuration

Using your running kernel's config as the starting point is the safest approach. Slackware stores the config in /boot:

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

If that file does not exist, try extracting it from the running kernel (requires CONFIG_IKCONFIG_PROC=y in the old kernel):

zcat /proc/config.gz > .config

Step 5: Update the Config Without Interactive Prompts

Rather than make oldconfig (which asks about every new option), use olddefconfig. This silently sets all new configuration options to their upstream default values — no prompting required:

make olddefconfig

This will update .config to account for any new options introduced since your previous kernel version while keeping all your existing settings intact.

Step 6: Compile the Kernel

Use all available CPU cores to speed up the build. The -j flag sets the number of parallel jobs:

make -j$(nproc)

This step takes the most time. On a modern multi-core machine expect anywhere from a few minutes to half an hour depending on hardware.

Step 7: Install the Kernel Modules

make modules_install

This installs the compiled modules into /lib/modules/6.18.0/ (or whichever version string the kernel reports).

Step 8: Copy the Kernel Image and System Map

Copy the kernel image and the symbol map to /boot regardless of which bootloader you are using:

cp arch/x86/boot/bzImage /boot/vmlinuz-6.18
cp System.map /boot/System.map-6.18

Optionally update the convenience symlinks that bootloader scripts expect:

ln -sf /boot/vmlinuz-6.18 /boot/vmlinuz
ln -sf /boot/System.map-6.18 /boot/System.map

Step 9: Copy the Kernel Config (Optional but Recommended)

Saving the config to /boot makes it easy to use as a base for future builds:

cp .config /boot/config-6.18

Step 10: Install the Kernel — LILO or ELILO

Follow the section that matches your system. If you are unsure which bootloader you have, check whether your system booted in EFI mode:

ls /sys/firmware/efi

If that directory exists, your system is using EFI and you should follow the ELILO section. If the directory is absent, follow LILO.

Step 10a: Update LILO (BIOS/legacy boot)

Edit /etc/lilo.conf to add an entry for the new kernel. Add it alongside (not replacing) your existing entry so you can fall back if needed:

image = /boot/vmlinuz-6.18
  root = /dev/sda1
  label = Linux-6.18
  read-only

Important: Adjust root = /dev/sda1 to match your actual root partition. Check your existing entries in lilo.conf for reference.

After editing, run LILO to write the new bootloader configuration:

lilo

LILO should print the names of each configured boot entry. If it exits cleanly, the bootloader has been updated. Continue to Step 11.

Step 10b: Update ELILO (EFI/VM with EFI firmware)

ELILO is the EFI counterpart to LILO and is what Slackware uses on EFI systems, including virtual machines configured with EFI firmware (e.g., VMware, VirtualBox, or QEMU/KVM with OVMF).

Confirm the EFI System Partition is mounted

The EFI System Partition (ESP) is typically mounted at /boot/efi. Verify it is mounted:

mount | grep efi

If it is not mounted, mount it manually (adjust the device as needed — check lsblk or /etc/fstab for your ESP device):

mount /dev/sda1 /boot/efi

Locate the ELILO directory

Slackware's ELILO files live under the ESP at:

/boot/efi/EFI/Slackware/

Confirm this path exists:

ls /boot/efi/EFI/Slackware/

You should see at minimum elilo.efi and elilo.conf.

Copy the kernel to the ESP

ELILO needs the kernel image directly on the EFI partition:

cp /boot/vmlinuz-6.18 /boot/efi/EFI/Slackware/vmlinuz-6.18

Edit elilo.conf

Open /boot/efi/EFI/Slackware/elilo.conf in a text editor and add a new entry for the 6.18 kernel. Add it alongside the existing entry, not replacing it:

image=vmlinuz-6.18
  label=Linux-6.18
  root=/dev/sda2
  read-only
  append="quiet"

A minimal elilo.conf with both the old and new entries might look like this:

prompt
timeout=50
default=Linux-6.18

image=vmlinuz-6.18
  label=Linux-6.18
  root=/dev/sda2
  read-only

image=vmlinuz
  label=Linux-previous
  root=/dev/sda2
  read-only

Important: Adjust root=/dev/sda2 to match your actual root partition. The image= path is relative to the directory containing elilo.conf on the ESP — do not use a full filesystem path here.

Run elilo to register the bootloader

elilo

This writes the updated configuration. If elilo is not in your PATH, it may be at /usr/sbin/elilo.

Step 11: Reboot

reboot
  • LILO systems: At the LILO prompt, select the Linux-6.18 entry (or wait for the default).
  • ELILO/EFI systems: The EFI firmware boot menu should present the Linux-6.18 label, or ELILO will boot the default entry after the timeout.

Once booted, verify the running kernel version:

uname -r

This should report 6.18.0 (or the point release you compiled).

Troubleshooting Tips

  • Missing kernel modules at boot: Check that make modules_install completed without errors and that /lib/modules/6.18.0/ exists with content.
  • LILO reports errors: Double-check partition names and file paths in /etc/lilo.conf. Remember to re-run lilo after any edit.
  • ELILO: kernel not found: Ensure the kernel image was copied to the ESP (/boot/efi/EFI/Slackware/) and that the image= name in elilo.conf matches the copied filename exactly.
  • ELILO: ESP not mounted at boot: Add the ESP to /etc/fstab so it mounts automatically. A typical fstab entry looks like: UUID=<esp-uuid> /boot/efi vfat defaults 0 2. Find the UUID with blkid.
  • Build fails on a header: Install the missing -devel package via Slackware's package tools or from the original installation media (slackpkg if configured, or manual installpkg).
  • Kernel panics at boot: Reboot and select your previous kernel entry from the LILO or ELILO menu to recover.
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