Compiling Linux Kernel from Source

Compiling Linux Kernel from Source | Generated by AI

Home 2026.06

Question: How do I compile the Linux kernel from source?

Answer:

# 1. Get the source (mainline or a stable tag)
git clone --depth 1 --branch v6.12 \
  https://github.com/torvalds/linux.git
cd linux

# 2. Install build deps (Ubuntu)
sudo apt install -y build-essential libncurses-dev bison flex \
  libssl-dev libelf-dev bc dwarves zstd

# 3. Start from your running kernel's config (fast path)
cp /boot/config-$(uname -r) .config
make olddefconfig          # fill new symbols with defaults
# or: make menuconfig       # TUI to tweak options
# or: make defconfig        # arch default config from scratch

# 4. Build (use all cores)
make -j$(nproc)            # builds vmlinux + modules

# 5a. Just the kernel image
make -j$(nproc) bzImage    # -> arch/x86/boot/bzImage

# 5b. Install (modules + image + initramfs + grub)
sudo make modules_install   # -> /lib/modules/<ver>/
sudo make install           # -> /boot, updates initramfs & grub

Key knobs:

make -j$(nproc) — parallel build; full kernel ~5–30 min depending on config/cores. On your 192GB MI300X box it’ll fly; on the M2 Air a tinyconfig build is saner.
localmodconfig — only build modules currently loaded (lsmod), drastically cuts build time:
```
make localmodconfig
```

O= — out-of-tree build dir to keep the source clean:

make O=../build defconfig
make O=../build -j$(nproc)

CC=clang LLVM=1 — build with Clang/LLVM instead of GCC.
make clean (keep config) / make mrproper (nuke config too).

Minimal config for fast iteration (e.g. learning, QEMU boots):

make tinyconfig
make -j$(nproc)
# boot it without touching your real system:
qemu-system-x86_64 -kernel arch/x86/boot/bzImage \
  -append "console=ttyS0" -nographic

If you just want a single module or subsystem, build that subtree:

make -j$(nproc) drivers/net/        # trailing slash = build dir
make M=drivers/mydriver modules     # external/standalone module

What’s the goal — booting a custom kernel, building one driver, or studying internals? The config strategy differs a lot (full distro config vs. tinyconfig + QEMU).

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