From 2e7ebf8bf3b24bce77e6cf161c49d18591a1b4c1 Mon Sep 17 00:00:00 2001
From: Pratham Patel <ppatel@ciq.com>
Date: Mon, 14 Jul 2025 22:04:55 +0530
Subject: [PATCH] kernel_remove: init script to remove a specified kernel

This script basically cleans up all the possible paths that might be
populated from a `make modules_install` and `make install`. Given that
the kernel is removed, the grub entry is also removed with the help of
`grubby`.

This is an ad-hoc script created to quickly remove a kernel without much
fuss about it.
---
 README.md        | 38 ++++++++++++++++++++++++++++++++++++++
 kernel_remove.sh | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100755 kernel_remove.sh

diff --git a/README.md b/README.md
index 6b24fe1..f21d3fa 100644
--- a/README.md
+++ b/README.md
@@ -80,3 +80,41 @@ This is the full script that end with the engineer ready to reboot the VM into t
 
 ### kernel_recompile_kabi.sh
 Will only recompile the kernel and check the KABI.
+
+### kernel_remove.sh
+This script is intended to clean up "development" kernels. By
+"development" kernels, the author means such a kernel that was built
+locally for testing if patch(es) for a CVE or customer request apply
+correctly and test them. Mainly, it means kernels installed using
+`make`, instead of as an RPM package.
+
+The script accepts **only one** `kernel release` (`uname -r`) to
+remove. Like so:
+```bash
+$ ./kernel_remove.sh 4.18.0-ciqlts8_6-83208b00c+
++ requested_kernel_to_remove=4.18.0-ciqlts8_6-83208b00c+
+++ rpm -q kernel-core --qf '%{VERSION}-%{RELEASE}\n'
+++ sort --version-sort
+++ tail -1
++ latest_rpm_kernel=4.18.0-372.32.1.el8_6.86ciq_lts.12.1
+++ uname -r
++ current_kernel=4.18.0-372.32.1.el8_6.86ciq_lts.12.1.x86_64
++ '[' -z 4.18.0-ciqlts8_6-83208b00c+ ']'
++ '[' 4.18.0-ciqlts8_6-83208b00c+ == 4.18.0-372.32.1.el8_6.86ciq_lts.12.1 ']'
+++ uname -m
++ '[' 4.18.0-ciqlts8_6-83208b00c+ == 4.18.0-372.32.1.el8_6.86ciq_lts.12.1.x86_64 ']'
++ '[' 4.18.0-ciqlts8_6-83208b00c+ == 4.18.0-372.32.1.el8_6.86ciq_lts.12.1.x86_64 ']'
++ '[' -d /lib/modules/4.18.0-ciqlts8_6-83208b00c+ ']'
++ sudo rm -fr /lib/modules/4.18.0-ciqlts8_6-83208b00c+
++ '[' -d /boot/dtb-4.18.0-ciqlts8_6-83208b00c+ ']'
++ '[' -f /boot/config-4.18.0-ciqlts8_6-83208b00c+ ']'
++ '[' -f /boot/initramfs-4.18.0-ciqlts8_6-83208b00c+.img ']'
++ sudo rm -f /boot/initramfs-4.18.0-ciqlts8_6-83208b00c+.img
++ '[' -f /boot/symvers-4.18.0-ciqlts8_6-83208b00c+.xz ']'
++ '[' -f /boot/symvers-4.18.0-ciqlts8_6-83208b00c+.gz ']'
++ '[' -f /boot/System.map-4.18.0-ciqlts8_6-83208b00c+ ']'
++ sudo rm -f /boot/System.map-4.18.0-ciqlts8_6-83208b00c+
++ '[' -f /boot/vmlinuz-4.18.0-ciqlts8_6-83208b00c+ ']'
++ sudo rm -f /boot/vmlinuz-4.18.0-ciqlts8_6-83208b00c+
++ sudo grubby --remove-kernel=/boot/vmlinuz-4.18.0-ciqlts8_6-83208b00c+
+```
diff --git a/kernel_remove.sh b/kernel_remove.sh
new file mode 100755
index 0000000..b4d218c
--- /dev/null
+++ b/kernel_remove.sh
@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+set -xeuf -o pipefail
+
+requested_kernel_to_remove="${1:-}"
+rpm_kernels=( $(rpm -q kernel-core --qf "%{VERSION}-%{RELEASE}\n" 2>/dev/null | tr '\n' ' ') )
+current_kernel="$(uname -r)"
+
+if [ -z "${requested_kernel_to_remove}" ]; then
+    echo 'Specify the kernel version'
+    echo 'Look under /lib/modules/ for "correct" versions'
+    exit 1
+fi
+
+for rpm_kernel in "${rpm_kernels[@]}"; do
+    if [ "${requested_kernel_to_remove}" == "${rpm_kernel}" ] || [ "${requested_kernel_to_remove}" == "${rpm_kernel}.$(uname -m)" ]; then
+        echo 'ERROR: Will not remove a kernel installed as an RPM package'
+        exit 1
+    fi
+done
+
+if [ "${requested_kernel_to_remove}" == "${current_kernel}" ]; then
+    echo 'ERROR: Will not remove the current kernel'
+    exit 1
+else
+    # The checks exist to prevent "no such [file|directory] found" "errors" on console
+    # Also helps with error management
+    [ -d "/lib/modules/${requested_kernel_to_remove}" ] && sudo rm -fr "/lib/modules/${requested_kernel_to_remove}"
+    [ -d "/boot/dtb-${requested_kernel_to_remove}" ] && sudo rm -fr "/boot/dtb-${requested_kernel_to_remove}"
+    [ -f "/boot/config-${requested_kernel_to_remove}" ] && sudo rm -f "/boot/config-${requested_kernel_to_remove}"
+    [ -f "/boot/initramfs-${requested_kernel_to_remove}.img" ] && sudo rm -f "/boot/initramfs-${requested_kernel_to_remove}.img"
+    [ -f "/boot/symvers-${requested_kernel_to_remove}.xz" ] && sudo rm -f "/boot/symvers-${requested_kernel_to_remove}.xz"
+    [ -f "/boot/symvers-${requested_kernel_to_remove}.gz" ] && sudo rm -f "/boot/symvers-${requested_kernel_to_remove}.gz"
+    [ -f "/boot/System.map-${requested_kernel_to_remove}" ] && sudo rm -f "/boot/System.map-${requested_kernel_to_remove}"
+    [ -f "/boot/vmlinuz-${requested_kernel_to_remove}" ] && sudo rm -f "/boot/vmlinuz-${requested_kernel_to_remove}"
+    # If $requested_kernel_to_remove is current default kernel, grubby will make the next-in-line kernel default
+    sudo grubby --remove-kernel="/boot/vmlinuz-${requested_kernel_to_remove}"
+fi