Adolfo Delorenzo
efc7f80b65
Security hardening: bind kubeconfig server to localhost, mount hardening (noexec/nosuid/nodev on tmpfs), sysctl network hardening, kernel module loading lock after boot, SHA256 checksum verification for downloads, kernel AppArmor + Audit support, complain-mode AppArmor profiles for containerd and kubelet, and security integration test. ARM64 Raspberry Pi support: piCore64 base extraction, RPi kernel build from raspberrypi/linux fork, RPi firmware fetch, SD card image with 4- partition GPT and tryboot A/B mechanism, BootEnv Go interface abstracting GRUB vs RPi boot environments, architecture-aware build scripts, QEMU aarch64 dev VM and boot test. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
221 lines
7.6 KiB
Bash
Executable File
221 lines
7.6 KiB
Bash
Executable File
#!/bin/bash
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# build-kernel.sh — Build custom Tiny Core kernel with CONFIG_CGROUP_BPF=y
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#
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# The stock Tiny Core 17.0 kernel (6.18.2-tinycore64) lacks CONFIG_CGROUP_BPF,
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# which is required for cgroup v2 device control in runc/containerd.
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# This script downloads the TC-patched kernel source, enables CONFIG_CGROUP_BPF,
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# and builds vmlinuz + modules.
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#
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# Output is cached in $CACHE_DIR/custom-kernel/ and reused across builds.
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set -euo pipefail
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SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
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PROJECT_ROOT="$(cd "$SCRIPT_DIR/../.." && pwd)"
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CACHE_DIR="${CACHE_DIR:-$PROJECT_ROOT/build/cache}"
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# shellcheck source=../config/versions.env
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. "$SCRIPT_DIR/../config/versions.env"
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KVER="6.18.2-tinycore64"
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KERNEL_BASE_URL="https://distro.ibiblio.org/tinycorelinux/${TINYCORE_VERSION%%.*}.x/${TINYCORE_ARCH}/release/src/kernel"
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KERNEL_SRC_URL="${KERNEL_BASE_URL}/linux-6.18.2-patched.tar.xz"
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KERNEL_CFG_URL="${KERNEL_BASE_URL}/config-${KVER}"
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CUSTOM_KERNEL_DIR="$CACHE_DIR/custom-kernel"
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CUSTOM_VMLINUZ="$CUSTOM_KERNEL_DIR/vmlinuz"
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CUSTOM_MODULES="$CUSTOM_KERNEL_DIR/modules"
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mkdir -p "$CACHE_DIR" "$CUSTOM_KERNEL_DIR"
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# --- Skip if already built ---
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if [ -f "$CUSTOM_VMLINUZ" ] && [ -d "$CUSTOM_MODULES/lib/modules/$KVER" ]; then
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echo "==> Custom kernel already built (cached)"
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echo " vmlinuz: $CUSTOM_VMLINUZ ($(du -h "$CUSTOM_VMLINUZ" | cut -f1))"
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MOD_COUNT=$(find "$CUSTOM_MODULES/lib/modules/$KVER" -name '*.ko*' | wc -l)
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echo " Modules: $MOD_COUNT modules in $CUSTOM_MODULES/lib/modules/$KVER"
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exit 0
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fi
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echo "==> Building custom kernel with CONFIG_CGROUP_BPF=y..."
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echo " Kernel version: $KVER"
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# --- Download kernel source ---
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KERNEL_SRC_ARCHIVE="$CACHE_DIR/linux-6.18.2-patched.tar.xz"
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if [ ! -f "$KERNEL_SRC_ARCHIVE" ]; then
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echo "==> Downloading kernel source (~149 MB)..."
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echo " URL: $KERNEL_SRC_URL"
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wget -q --show-progress -O "$KERNEL_SRC_ARCHIVE" "$KERNEL_SRC_URL" 2>/dev/null || \
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curl -fSL "$KERNEL_SRC_URL" -o "$KERNEL_SRC_ARCHIVE"
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echo " Downloaded: $(du -h "$KERNEL_SRC_ARCHIVE" | cut -f1)"
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else
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echo "==> Kernel source already cached: $(du -h "$KERNEL_SRC_ARCHIVE" | cut -f1)"
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fi
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# --- Download stock config ---
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KERNEL_CFG="$CACHE_DIR/config-${KVER}"
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if [ ! -f "$KERNEL_CFG" ]; then
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echo "==> Downloading stock kernel config..."
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echo " URL: $KERNEL_CFG_URL"
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wget -q -O "$KERNEL_CFG" "$KERNEL_CFG_URL" 2>/dev/null || \
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curl -fSL "$KERNEL_CFG_URL" -o "$KERNEL_CFG"
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else
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echo "==> Stock kernel config already cached"
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fi
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# --- Extract source ---
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# IMPORTANT: Must extract on a case-sensitive filesystem. The kernel source has
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# files that differ only by case (e.g., xt_mark.h vs xt_MARK.h). If the cache
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# is on macOS (case-insensitive APFS), extraction silently loses files.
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# Use /tmp inside the container (ext4, case-sensitive) for the build.
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KERNEL_BUILD_DIR="/tmp/kernel-build"
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rm -rf "$KERNEL_BUILD_DIR"
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mkdir -p "$KERNEL_BUILD_DIR"
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echo "==> Extracting kernel source (case-sensitive filesystem)..."
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tar -xf "$KERNEL_SRC_ARCHIVE" -C "$KERNEL_BUILD_DIR"
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# Find the extracted source directory (could be linux-6.18.2 or linux-6.18.2-patched)
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KERNEL_SRC_DIR=$(find "$KERNEL_BUILD_DIR" -maxdepth 1 -type d -name 'linux-*' | head -1)
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if [ -z "$KERNEL_SRC_DIR" ]; then
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echo "ERROR: Could not find kernel source directory after extraction"
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ls -la "$KERNEL_BUILD_DIR"/
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exit 1
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fi
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echo " Source dir: $(basename "$KERNEL_SRC_DIR")"
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cd "$KERNEL_SRC_DIR"
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# --- Apply stock config + enable CONFIG_CGROUP_BPF ---
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echo "==> Applying stock Tiny Core config..."
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cp "$KERNEL_CFG" .config
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echo "==> Enabling required kernel configs..."
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./scripts/config --enable CONFIG_CGROUP_BPF
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./scripts/config --enable CONFIG_DEVTMPFS
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./scripts/config --enable CONFIG_DEVTMPFS_MOUNT
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./scripts/config --enable CONFIG_MEMCG
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./scripts/config --enable CONFIG_CFS_BANDWIDTH
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# Security: AppArmor LSM + Audit subsystem
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echo "==> Enabling AppArmor + Audit kernel configs..."
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./scripts/config --enable CONFIG_AUDIT
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./scripts/config --enable CONFIG_AUDITSYSCALL
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./scripts/config --enable CONFIG_SECURITY
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./scripts/config --enable CONFIG_SECURITYFS
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./scripts/config --enable CONFIG_SECURITY_NETWORK
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./scripts/config --enable CONFIG_SECURITY_APPARMOR
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./scripts/config --set-str CONFIG_LSM "lockdown,yama,apparmor"
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./scripts/config --set-str CONFIG_DEFAULT_SECURITY "apparmor"
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# --- Strip unnecessary subsystems for smallest footprint ---
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# This is a headless K8s edge appliance — no sound, GPU, wireless, etc.
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echo "==> Disabling unnecessary subsystems for minimal footprint..."
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# Sound subsystem (not needed on headless appliance)
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./scripts/config --disable SOUND
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# GPU/DRM (serial console only, no display)
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./scripts/config --disable DRM
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# KVM hypervisor (this IS the guest/bare metal, not a hypervisor)
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./scripts/config --disable KVM
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# Media/camera/TV/radio (not needed)
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./scripts/config --disable MEDIA_SUPPORT
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# Wireless networking (wired edge device)
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./scripts/config --disable WIRELESS
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./scripts/config --disable WLAN
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./scripts/config --disable CFG80211
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# Bluetooth (not needed)
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./scripts/config --disable BT
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# NFC (not needed)
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./scripts/config --disable NFC
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# Infiniband (not needed on edge)
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./scripts/config --disable INFINIBAND
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# PCMCIA (legacy, not needed)
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./scripts/config --disable PCMCIA
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# Amateur radio (not needed)
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./scripts/config --disable HAMRADIO
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# ISDN (not needed)
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./scripts/config --disable ISDN
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# ATM networking (not needed)
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./scripts/config --disable ATM
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# Joystick/gamepad (not needed)
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./scripts/config --disable INPUT_JOYSTICK
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./scripts/config --disable INPUT_TABLET
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# FPGA (not needed)
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./scripts/config --disable FPGA
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# Resolve dependencies (olddefconfig accepts defaults for new options)
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make olddefconfig
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# Verify CONFIG_CGROUP_BPF is set
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if grep -q 'CONFIG_CGROUP_BPF=y' .config; then
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echo " CONFIG_CGROUP_BPF=y confirmed in .config"
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else
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echo "ERROR: CONFIG_CGROUP_BPF not set after olddefconfig"
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grep 'CGROUP_BPF' .config || echo " (CGROUP_BPF not found in .config)"
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echo ""
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echo "Prerequisites check:"
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grep -E 'CONFIG_BPF=|CONFIG_BPF_SYSCALL=' .config || echo " BPF not found"
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exit 1
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fi
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# Show what changed
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echo " Config diff from stock:"
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diff "$KERNEL_CFG" .config | grep '^[<>]' | head -20 || echo " (no differences beyond CGROUP_BPF)"
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# --- Build kernel + modules ---
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NPROC=$(nproc 2>/dev/null || echo 4)
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echo ""
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echo "==> Building kernel (${NPROC} parallel jobs)..."
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echo " This may take 15-25 minutes..."
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make -j"$NPROC" bzImage modules 2>&1
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echo "==> Kernel build complete"
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# --- Install to staging ---
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echo "==> Installing vmlinuz..."
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cp arch/x86/boot/bzImage "$CUSTOM_VMLINUZ"
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echo "==> Installing modules (stripped)..."
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rm -rf "$CUSTOM_MODULES"
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mkdir -p "$CUSTOM_MODULES"
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make INSTALL_MOD_STRIP=1 modules_install INSTALL_MOD_PATH="$CUSTOM_MODULES"
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# Remove build/source symlinks (they point to the build dir which won't exist in rootfs)
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rm -f "$CUSTOM_MODULES/lib/modules/$KVER/build"
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rm -f "$CUSTOM_MODULES/lib/modules/$KVER/source"
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# Run depmod to generate proper module dependency files
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echo "==> Running depmod..."
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depmod -a -b "$CUSTOM_MODULES" "$KVER" 2>/dev/null || true
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# Save the final config for reference
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cp .config "$CUSTOM_KERNEL_DIR/.config"
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# --- Clean up build dir (large, ~1.5 GB) ---
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echo "==> Cleaning kernel build directory..."
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cd /
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rm -rf "$KERNEL_BUILD_DIR"
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# --- Summary ---
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echo ""
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echo "==> Custom kernel build complete:"
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echo " vmlinuz: $CUSTOM_VMLINUZ ($(du -h "$CUSTOM_VMLINUZ" | cut -f1))"
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MOD_COUNT=$(find "$CUSTOM_MODULES/lib/modules/$KVER" -name '*.ko*' | wc -l)
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echo " Modules: $MOD_COUNT modules"
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echo " Modules size: $(du -sh "$CUSTOM_MODULES/lib/modules/$KVER" | cut -f1)"
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echo ""
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