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Commit fdc540f

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authored
Merge pull request #81 from shengwen-tw/switch_root
Support mounting rootfs from virtio-blk via initrd
2 parents 81e61bc + 762e4ed commit fdc540f

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4 files changed

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4 files changed

+224
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‎README.md

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@@ -90,10 +90,56 @@ You can exit the emulator using: \<Ctrl-a x\>. (press Ctrl+A, leave it, afterwar
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An automated build script is provided to compile the RISC-V cross-compiler, Busybox, and Linux kernel from source.
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Please note that it only supports the Linux host environment.
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To build everything, simply run:
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```shell
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$ make build-image
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```
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This command invokes the underlying script: `scripts/build-image.sh`, which also offers more flexible usage options.
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### Script Usage
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```
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./scripts/build-image.sh [--buildroot] [--linux] [--all] [--external-root] [--clean-build] [--help]
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Options:
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--buildroot Build Buildroot rootfs
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--linux Build Linux kernel
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--all Build both Buildroot and Linux
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--external-root Use external rootfs instead of initramfs
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--clean-build Remove entire buildroot/ and/or linux/ directories before build
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--help Show this message
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```
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### Examples
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Build the Linux kernel only:
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```
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$ scripts/build-image.sh --linux
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```
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Build Buildroot only:
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```
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$ scripts/build-image.sh --buildroot
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```
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Build Buildroot and generate an external root file system (ext4 image):
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```
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$ scripts/build-image.sh --buildroot --external-root
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```
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Force a clean build:
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```
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$ scripts/build-image.sh --all --clean-build
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$ scripts/build-image.sh --linux --clean-build
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$ scripts/build-image.sh --buildroot --clean-build
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```
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## License
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`semu` is released under the MIT License.

‎scripts/build-image.sh

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@@ -19,11 +19,31 @@ function OK
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PARALLEL="-j$(nproc)"
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function safe_copy {
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local src="1ドル"
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local dst="2ドル"
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if [ ! -f "$dst" ]; then
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echo "Copying $src -> $dst"
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cp -f "$src" "$dst"
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else
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echo "$dst already exists, skipping copy"
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fi
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}
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function do_buildroot
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{
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ASSERT git clone https://github.com/buildroot/buildroot -b 2024年11月1日 --depth=1
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cp -f configs/buildroot.config buildroot/.config
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cp -f configs/busybox.config buildroot/busybox.config
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if [ ! -d buildroot ]; then
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echo "Cloning Buildroot..."
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ASSERT git clone https://github.com/buildroot/buildroot -b 2024年11月1日 --depth=1
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else
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echo "buildroot/ already exists, skipping clone"
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fi
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safe_copy configs/buildroot.config buildroot/.config
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safe_copy configs/busybox.config buildroot/busybox.config
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cp -f target/init buildroot/fs/cpio/init
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# Otherwise, the error below raises:
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# You seem to have the current working directory in your
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# LD_LIBRARY_PATH environment variable. This doesn't work.
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ASSERT make olddefconfig
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ASSERT make $PARALLEL
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popd
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cp -f buildroot/output/images/rootfs.cpio ./
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if [[ $EXTERNAL_ROOT -eq 1 ]]; then
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echo "Copying rootfs.cpio to rootfs_full.cpio (external root mode)"
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cp -f buildroot/output/images/rootfs.cpio ./rootfs_full.cpio
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ASSERT ./scripts/rootfs_ext4.sh
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else
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echo "Copying rootfs.cpio to rootfs.cpio (initramfs mode)"
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cp -f buildroot/output/images/rootfs.cpio ./rootfs.cpio
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fi
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}
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function do_linux
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{
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ASSERT git clone https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git -b linux-6.12.y --depth=1
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cp -f configs/linux.config linux/.config
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if [ ! -d linux ]; then
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echo "Cloning Linux kernel..."
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ASSERT git clone https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git -b linux-6.12.y --depth=1
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else
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echo "linux/ already exists, skipping clone"
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fi
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safe_copy configs/linux.config linux/.config
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export PATH="$PWD/buildroot/output/host/bin:$PATH"
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export CROSS_COMPILE=riscv32-buildroot-linux-gnu-
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export ARCH=riscv
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popd
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}
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do_buildroot && OK
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do_linux && OK
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function show_help {
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cat << EOF
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Usage: 0ドル [--buildroot] [--linux] [--all] [--external-root] [--clean-build] [--help]
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Options:
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--buildroot Build Buildroot rootfs
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--linux Build Linux kernel
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--all Build both Buildroot and Linux
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--external-root Use external rootfs instead of initramfs
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--clean-build Remove entire buildroot/ and/or linux/ directories before build
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--help Show this message
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EOF
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exit 1
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}
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BUILD_BUILDROOT=0
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BUILD_LINUX=0
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EXTERNAL_ROOT=0
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CLEAN_BUILD=0
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while [[ $# -gt 0 ]]; do
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case "1ドル" in
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--buildroot)
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BUILD_BUILDROOT=1
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;;
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--linux)
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BUILD_LINUX=1
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;;
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--all)
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BUILD_BUILDROOT=1
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BUILD_LINUX=1
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;;
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--external-root)
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EXTERNAL_ROOT=1
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;;
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--clean-build)
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CLEAN_BUILD=1
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;;
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--help|-h)
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show_help
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;;
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*)
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echo "Unknown option: 1ドル"
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show_help
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;;
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esac
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shift
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done
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if [[ $BUILD_BUILDROOT -eq 0 && $BUILD_LINUX -eq 0 ]]; then
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echo "Error: No build target specified. Use --buildroot, --linux, or --all."
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show_help
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fi
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if [[ $CLEAN_BUILD -eq 1 && $BUILD_BUILDROOT -eq 1 && -d buildroot ]]; then
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echo "Removing buildroot/ for clean build..."
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rm -rf buildroot
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fi
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if [[ $CLEAN_BUILD -eq 1 && $BUILD_LINUX -eq 1 && -d linux ]]; then
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echo "Removing linux/ for clean build..."
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rm -rf linux
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fi
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if [[ $BUILD_BUILDROOT -eq 1 ]]; then
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do_buildroot && OK
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fi
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if [[ $BUILD_LINUX -eq 1 ]]; then
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do_linux && OK
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fi

‎scripts/rootfs_ext4.sh

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#!/usr/bin/bash
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ROOTFS_CPIO="rootfs_full.cpio"
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IMG="ext4.img"
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IMG_SIZE=$((1024 * 1024 * 1024)) # 1GB
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IMG_SIZE_BLOCKS=$((${IMG_SIZE} / 4096)) # IMG_SIZE / 4k
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DIR=rootfs
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echo "[*] Remove old rootfs directory..."
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rm -rf $DIR
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mkdir -p $DIR
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echo "[*] Extract CPIO"
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pushd $DIR
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cpio -idmv < ../$ROOTFS_CPIO
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popd
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echo "[*] Create empty image"
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dd if=/dev/zero of=${IMG} bs=4k count=${IMG_SIZE_BLOCKS}
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echo "[*] Create ext4 rootfs image"
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fakeroot mkfs.ext4 -F ${IMG} -d $DIR
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# Show image size
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du -h ${IMG}

‎target/init

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#!/bin/sh
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export PATH=/bin:/sbin:/usr/bin:/usr/sbin
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ROOTFS_DEV=/dev/vda
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mount -t devtmpfs devtmpfs /dev
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mount -t proc none /proc
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mount -t sysfs none /sys
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# use the /dev/console device node from devtmpfs if possible to not
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# confuse glibc's ttyname_r().
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# This may fail (e.g., booted with console=), and errors from exec will
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# terminate the shell, so use a subshell for the test
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if (exec 0</dev/console) 2>/dev/null; then
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exec 0</dev/console
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exec 1>/dev/console
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exec 2>/dev/console
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fi
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echo "[*] Attempting to mount $ROOTFS_DEV"
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mkdir -p /mnt
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mount -t ext4 $ROOTFS_DEV /mnt
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if [ $? -ne 0 ]; then
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echo "[!] Failed to mount $ROOTFS_DEV. Using initramfs."
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exec /sbin/init "$@"
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fi
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echo "[*] $ROOTFS_DEV mounted successfully. Checking for root filesystem..."
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if [ -x /mnt/sbin/init ]; then
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echo "[*] Valid root filesystem found. Switching root to $ROOTFS_DEV"
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mount --move /sys /mnt/sys
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mount --move /proc /mnt/proc
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mount --move /dev /mnt/dev
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exec switch_root -c /dev/console /mnt /sbin/init "$@"
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else
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echo "[!] No valid root filesystem found on $ROOTFS_DEV. Using initramfs."
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umount /mnt
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exec /sbin/init "$@"
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fi

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