tsiry-sandratraina.com
Simple script and config (type-safe) for building custom Linux kernels for Firecracker MicroVMs
Refactor build script to improve kernel version validation and streamline repository cloning logic
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build.sh
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build.sh
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#!/usr/bin/env bash
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set -e
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readonly MAGENTA="$(tput setaf 5 2>/dev/null || echo '')"
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readonly ORANGE="$(tput setaf 3 2>/dev/null || echo '')"
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readonly NO_COLOR="$(tput sgr0 2>/dev/null || echo '')"
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if [[ ! "$1" =~ ^[0-9]+\.[0-9]+(\.[0-9]+|\.y)?$ ]]; then
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echo "${ORANGE}Error: Invalid kernel version format '${1}'. Expected format is X.Y or X.Y.Z (where Z can be 'y' or a number).${NO_COLOR}"
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echo "Example: ./build.sh 6.1 or ./build.sh 6.1.12 or ./build.sh 6.1.y"
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if [[ $# -lt 1 ]]; then
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echo "${ORANGE}Usage: $0 <kernel-version>{.y|.Z}${NO_COLOR}"
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echo "Example: ./build.sh 6.1 | 6.1.12 | 6.1.y | v6.1.12"
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exit 1
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fi
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INPUT="$1"
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NUM="${INPUT#v}" # normalize by stripping optional leading 'v'
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# Validate: X.Y, X.Y.Z, or X.Y.y
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if [[ ! "$NUM" =~ ^[0-9]+\.[0-9]+(\.(y|[0-9]+))?$ ]]; then
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echo "${ORANGE}Error: Invalid kernel version '${INPUT}'. Expected X.Y, X.Y.Z, or X.Y.y${NO_COLOR}"
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echo "Examples: 6.1 | 6.1.12 | 6.1.y | v6.1.12"
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exit 1
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fi
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echo "Building vmlinux for Linux kernel ${CYAN}${1}${NO_COLOR}"
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echo "Building vmlinux for Linux kernel ${CYAN}${NUM}${NO_COLOR}"
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type apt-get > /dev/null && sudo apt-get install -y git build-essential flex bison libncurses5-dev libssl-dev gcc bc libelf-dev pahole || true
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type apt-get >/dev/null 2>&1 && sudo apt-get install -y git build-essential flex bison libncurses5-dev libssl-dev gcc bc libelf-dev pahole || true
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[ -d linux-stable ] || git clone --depth=1 -b linux-${1} git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
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REPO_URL="git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git"
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# Decide ref: maintenance branch vs tag
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if [[ "$NUM" == *".y" ]]; then
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REF="linux-${NUM}" # e.g. linux-6.16.y
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VERSION="${NUM%.y}" # e.g. 6.16
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else
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REF="v${NUM}" # e.g. v6.16.2 (ensure leading v)
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VERSION="${NUM}" # e.g. 6.16.2 (no leading v)
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fi
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if [[ ! -d linux-stable ]]; then
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# Clone directly at the desired ref (branch or tag)
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git clone --depth=1 --branch "$REF" "$REPO_URL" linux-stable
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else
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# Update existing checkout to the desired ref
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git -C linux-stable fetch --tags --force origin
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# Shallow-fetch the specific ref (works for both branches and tags)
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git -C linux-stable fetch --depth=1 origin "$REF":"$REF" || git -C linux-stable fetch origin "$REF":"$REF"
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git -C linux-stable checkout -f "$REF"
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fi
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cp .config linux-stable/.config
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cd linux-stable
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yes '' | make vmlinux -j$(nproc) < /dev/null
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# Build
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yes '' | make vmlinux -j"$(nproc)" < /dev/null
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VERSION=${1%.y}
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VMLINUX=$(echo vmlinux-${VERSION})
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mv vmlinux ${VMLINUX}.$(uname -m)
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VMLINUX="vmlinux-${VERSION}"
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mv vmlinux "${VMLINUX}.$(uname -m)"
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echo "${GREEN}vmlinux built successfully!${NO_COLOR}"
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echo "You can find the vmlinux file in ${CYAN}$(pwd)/${VMLINUX}.$(uname -m)${NO_COLOR}"
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exit 0