make config vs oldconfig vs defconfig vs menuconfig vs savedefconfig

-
Building the Linux Kernel is a two-step process:

  1. Configuring the Kernel options
  2. Building the Kernel with those options.
There are many methods available for configuring the kernel.

make config:
  • Text-based Configuration. 
  • Options are prompted one after another.
  • All options need to be answered
  • Access to former options is not possible


make menuconfig:
  • Menu-driven user interface
  • Allows to navigate forwards and backward directly between features
  • Allows to load and save files with filenames different from ".config"
  • Provides search feature
  • It uses ncurses library for GUI. If the ncurses library is not installed, make menuconfig option fails. To install ncurses library on Ubuntu: sudo apt-get install libncurses5-dev

make defconfig:

Creates a ".config" file with default options from the ARCH supplied defconfig

Configurations are generally stored in the directory: arch/$(ARCH)/configs


$ ls arch/x86/configs/
i386_defconfig  tiny.config  x86_64_defconfig  xen.config


When you run "make defconfig" on "x86" machine, it copies the configuration options from "i386_defconfig". On "X86_64" machine, it copies the configuration options from "x86_64_defconfig".


My system was "x86_64", so it copied kernel configuration from 'x86_64_defconfig'

When you are cross compiling, and there will be default configuration for that particular board in arch/(ARCH)/configs folder.



make oldconfig:

  • Reads the existing .config file and prompts the user for options in the current kernel source not found in the .config file.
  • Useful when you are moving the existing kernel configuration to a new kernel version.
  • If you run 'make oldconfig' second time after you have run it once, the second time will not ask you any options

make savedefconfig:

  • Creates a 'defconfig' file for you in the current directory.
  • Used when you do a 'make defconfig' and modified few configuration changes as per your new board


Note: New defconfig file name should end with "_defconfig"




Comments

Post a Comment

Popular posts from this blog

bb.utils.contains yocto

-
Image
bb.utils.contains  is most commonly used function in Yocto. grep in poky directory returned with 696 count. $ grep -nr 'bb.utils.contains' poky/ | wc -l 696 It's definition is present in 'poky/bitbake/lib/bb/utils.py' file This function returns third argument if the second argument is subset of the first argument else returns fourth argument Let's take an example to understand this. You can see from the above screenshot, when the second argument is a subset of first argument, "present" was returned, else "notpresent" was returned We can also use bb.utils.contains inside if loop. This we can use inside a recipe. if ${@bb.utils.contains('SOMEFLAG','NEWVALUE3','true','false',d)}; then     FOO = 'HELLO' fi
Read more

Difference between RDEPENDS and DEPENDS in Yocto

-
We normally observe these two (RDEPENDS and DEPENDS) whenever we open any recipe. What should we choose when we write our own recipe. DEPENDS -> Build Time Dependency RDEPENDS -> Run Time Dependency DEPENDS: When a recipe 'A' is DEPENDS on recipe 'B'. In this case, Bitbake first builds recipe 'B' and then recipe 'A' E.g. You need 'dbus' to be built before 'wpa_supplicant'. RDEPENDS: When a recipe 'A' is RDEPENDS on recipe 'B'. In this case, Bitbake deploys 'B' on the target system when it deploys 'A'.  E.g. 'perf' RDEPENDS on 'bash' In other words, DEPENDS are those set of packages that should be available while building package, whereas RDEPENDS are set of packages that should be available during execution of the program.
Read more

PR, PN and PV Variable in Yocto

-
PN : Represents the name of the recipe. The name is usually extracted from the recipe file name. PR:  Represents the revision of the recipe. Default value for this revision is "r0". Subsequent revisions of the recipe conventionally will have "r1", "r2" and so on. PV:  Represents the version of the recipe. Normally extracted from the recipe file name. For example: ffmpeg_3.4.2.bb recipe. ${PN} : ffmpeg ${PV} : 3.4.2
Read more