Linux kernel compilation

Prerequisites

Some prerequisites to compile the kernel include

kernel sources (obviously)
glibc kernheaders
glibc devel
cpp (c preprocessor)
binutils
gcc
flex and bison (I assume to parse the Kconfig language (and possibly other syntaxes))
ncurses (for make menuconfig)
tcl (for make xconfig)
tk (for make xconfig)

tk and tcl are required in configuration step

533 rene @ debian 14:15:28 ~/github/linux/temp/TODO/kernel/compilation/make-targets/tinyconfig/linux-src make tinyconfig
  HOSTCC  scripts/basic/fixdep
  HOSTCC  scripts/kconfig/conf.o
  HOSTCC  scripts/kconfig/confdata.o
  HOSTCC  scripts/kconfig/expr.o
  LEX     scripts/kconfig/lexer.lex.c
/bin/sh: 1: flex: not found

sudo apt install -y flex bison

Config options

UEFI needs these config options.

Default configuration

The kernel includes a default configuration.

The default configuration is presented the first time menuconfig is run on a source tree.

Specifying an alternate config file

By default, the make system uses ./.config as build configuration file.

An alternate file can be chosen by setting the environment variable KCONFIG_CONFIG to the path of a config file or specyfing the alternate config file directly like so:

make KCONFIG_CONFIG=test.config

Specifying a separate build directory

By default, the generated files go into the same tree as the kernel sources. Invoking make with O=/path/to/output/dir allows to specify an alternative destination

cd /usr/src/linux-4.X
make O=/home/name/build/kernel menuconfig
make O=/home/name/build/kernel
sudo make O=/home/name/build/kernel modules_install install

Verbosity level

make V=1 prints detailed compile and link commands.

make V=2 also prints why a target is rebuilt.

TODO

The compiled kernel should be placed under arch/x86/boot/bzImage.

scripts/config (in the Kernel source tree) allows to manipulate options in a .config file from the command line.