Linux Kernel Building

Configure and build Linux kernels for various architectures.

Kernel Source Setup

# Download kernel source
wget https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.6.tar.xz
tar xf linux-6.6.tar.xz
cd linux-6.6

Configuration

# Use default config for architecture
make defconfig

# Interactive menu configuration
make menuconfig

# Minimal config from running kernel
make localmodconfig

# Copy existing config
cp /boot/config-$(uname -r) .config
make olddefconfig

Key Configuration Options

# Enable initramfs support
CONFIG_BLK_DEV_INITRD=y

# Enable devtmpfs for automatic device nodes
CONFIG_DEVTMPFS=y
CONFIG_DEVTMPFS_MOUNT=y

# Enable required filesystems
CONFIG_TMPFS=y
CONFIG_PROC_FS=y
CONFIG_SYSFS=y

# Disable unneeded features for minimal kernel
CONFIG_MODULES=n
CONFIG_PRINTK=y

# Embedded initramfs (optional)
CONFIG_INITRAMFS_SOURCE="/path/to/initramfs"

Building

# Build kernel image (x86)
make bzImage -j$(nproc)

# Build kernel image (ARM)
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- zImage -j$(nproc)

# Build device tree blobs
make dtbs

# Build modules
make modules

Output Locations

• x86 kernel: arch/x86/boot/bzImage
• ARM kernel: arch/arm/boot/zImage
• Device trees: arch/arm/boot/dts/*.dtb
• System.map: System.map

Kernel Boot Parameters

Common kernel command line options:

console=ttyS0,115200       # Serial console
console=tty0               # VGA console
root=/dev/sda1             # Root filesystem device
rootwait                   # Wait for root device
rw                         # Mount root read-write
init=/sbin/init            # Init process path
rdinit=/init               # Initramfs init path
quiet                      # Suppress boot messages
debug                      # Enable debug messages

Testing with QEMU

qemu-system-x86_64 \
  -kernel arch/x86/boot/bzImage \
  -initrd /path/to/initramfs.cpio.gz \
  -append "console=ttyS0 rdinit=/init" \
  -nographic