Create a simple rootfs img by busybox for linux kernel launch.

mkrootfs.sh

#!/bin/bash
set -e

# 配置参数
ROOTFS_DIR="./rootfs"     # 根文件系统目录
OUTPUT_IMG="rootfs.img"   # 输出镜像文件名
IMG_SIZE="64M"            # 镜像大小
ARCH="aarch64"            # 目标架构 (x86_64/arm/aarch64)
KERNEL_PATH="./bzImage"   # 内核路径

# 清理旧文件
sudo umount -q "${ROOTFS_DIR}/mnt" 2>/dev/null || true
rm -rf "${ROOTFS_DIR}" "${OUTPUT_IMG}"

# 创建根文件系统目录结构
mkdir -p "${ROOTFS_DIR}"/{bin,dev,etc/init.d,lib,proc,sys,tmp,root,usr/{bin,lib},mnt}

# 复制 BusyBox 并创建符号链接
sudo cp /usr/bin/busybox "${ROOTFS_DIR}/bin/"
sudo chroot "${ROOTFS_DIR}" /bin/busybox --install /bin

# 生成启动脚本 /etc/init.d/rcS
cat > "${ROOTFS_DIR}/etc/init.d/rcS" <<EOF
#!/bin/sh
mount -t proc none /proc
mount -t sysfs none /sys

exec /bin/sh
EOF
sudo chmod +x "${ROOTFS_DIR}/etc/init.d/rcS"

# 创建磁盘镜像
dd if=/dev/zero of="${OUTPUT_IMG}" bs=${IMG_SIZE} count=1
mkfs.ext4 -F "${OUTPUT_IMG}"

# 挂载镜像并复制文件系统
MOUNT_DIR="./mnt"
mkdir -p "${MOUNT_DIR}"
sudo mount -o loop "${OUTPUT_IMG}" "${MOUNT_DIR}"
sudo cp -ra "${ROOTFS_DIR}/"* "${MOUNT_DIR}/"
sudo umount "${MOUNT_DIR}"
rm -rf "${MOUNT_DIR}"

# 清理临时目录
rm -rf "${ROOTFS_DIR}"

echo "--------------------------------------------------"
echo "rootfs.img 生成成功！使用以下命令启动 QEMU:"
echo "--------------------------------------------------"

# # QEMU 启动命令
# if [ "$ARCH" = "x86_64" ]; then
#   echo "qemu-system-x86_64 \\
#     -kernel \"${KERNEL_PATH}\" \\
#     -append \"console=ttyS0 root=/dev/sda rw init=/sbin/init\" \\
#     -drive \"file=${OUTPUT_IMG},format=raw\" \\
#     -nographic"
# elif [ "$ARCH" = "aarch64" ]; then
#   echo "qemu-system-aarch64 \\
#     -M virt \\
#     -cpu cortex-a53 \\
#     -kernel \"${KERNEL_PATH}\" \\
#     -append \"console=ttyAMA0 root=/dev/vda rw init=/sbin/init\" \\
#     -drive \"file=${OUTPUT_IMG},format=raw\" \\
#     -nographic"
# fi

sudo apt install busybox-static
install busybox static first.