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This chapter guides through the tasks which have to be done to create a user compiled kernel and root filesystem within a Linux system as mentioned in page "Board bring-up overview for TEI0022". It should be done in the following two three sections:

• Toolchain setup
• Kernel generation
• Root filesystem generation

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• Create a new folder in a known existing folder via mkdir toolchain
  
• Download the toolchain from linaro for the appropirate appropriate architecture and version via e.g. wget http://releases.linaro.org/components/toolchain/binaries/latest-7/arm-linux-gnueabihf/gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.xz
• Decompress the tar-archiv via tar -xvf gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf.tar.xz
• Set the CROSS_COMPILE variable to cross-compile the source code via export CROSS_COMPILE=$PWD/gcc-linaro-7.5.0-2019.12-x86_64_arm-linux-gnueabihf-arm-linux-gnueabihf/bin/arm-linux-gnueabihf-

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• Create a new folder in a known existing folder via mkdir software
• Change into the new folder via cd software
• Clone the git repository via git clone https://github.com/altera-opensource/linux-sodfpga.git
• Change into the new folder via cd linux-socfpga
• Look into the tags inside the repository via git tag -l rel*
• Select one of the tags and check it out via git checkout rel_socfpga-<selection>
• Load the default configuration for the kernel via make ARCH=arm socfpga_defconfig
• Install packages for kernel configuration via sudo apt-get install libncurses5-dev
• Open the kernel configuration dialogue via make ARCH=arm menuconfig
• Configure the kernel in this window:
  
  • General Setup → Disable Automatically append version information to the version string
  • Enable the block layer → Support for large (2TB+) block devices and files
• Generate the kernel via make ARCH=arm LOCALVERSION= zImage
• If the previous command does not work, try to use this one: make ARCH=arm CROSS-COMPILE=arm-linux-gnueabihf LOCALVERSION= zImage
• After compilation, which can can last a longer time, the kernel should be in folder arch/arm/boot

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• Create a new folder in a known existing folder via mkdir rootfs
• Change into the new folder via cd rootfs
  
• Clone the git repository via git cloneclone https://github.com/buildroot/buildroot
  
• Change into the new folder via cd buildroot
• Look into the branch overview inside the repository via git branch -a
  
• Select one of the branches and check it out via git checkout <selection>
• Open the buildroot configuration dialogue via make nconfig
• Configure the buildroot in this window:
  • Target options → Target Architecture → ARM (little endian)
  • Target options → Target Architecture Variant → cortex-A9
  • Target options → Target ABI → EABI
  • Target options → Enable NEON SIMD extension support
  • Target options → Floating point strategy → NEON
  • Toolchain → Toolchain type → Buildroot toolchain
  • System Configuration → System hostname → <Select a name>
  • System Configuration → System banner → <Select a system banner>
    
  • System Configuration → Init System → BusyBox
    
  • System Configuration → /dev management → Dynamic using devtmpfs only
    
  • System Configuration → Enable root login with password
    
  • System Configuration → Root password → root
    
  • System Configuration →Enable Run a getty (login prompt) after boot
    
  • Filesystem images → Enable tar the root filesystem
• Save the configuration via F6 → Enter → Enter
• Exit the configuration menu via F9
• Configure BusyBox if desired via make busybox-menuconfig
• Generate the root filesystem via make all
• After compilation, which can can last a longer time, the root filesystem (rootfs.tar) should be in folder buildroot/output/images/

This root filesystem is important to create the SD card for booting.