Kernel configurations

Based on Configurations

• Config | Gentoo | Development Workstation Install
• Config | Gentoo | Docker on Development machine

TODO

• Compare "make tinyconfig" to default hardend gentoo kernel config and see what else can be removed. Base kernel settings below on delta from tinyconfig to used config

Build Settings

• Binary blobs¹

  • Remove freedist from ACCEPT_LICENSE

    • /etc/portage/make.conf

      ACCEPT_LICENSE="-* @FREE"

  • Deblog kernel sources on extraction

    • /etc/portage/package.use

      # Deblob kernel sources
      sys-kernel/gentoo-sources deblob

Kernel settings

The linux kernel has a myriad of settings. Below are the settings that I either

• make sure are turned on
• turn off all the time
• have selected based on the specified conditions

All other settings have been left on default

• General setup
  • Local Version - YYYYMMDD-## where ## is one up number when building more than one version a day
  • Control Group Support
    • Freezer cgroup subsystem - built-in - required by app-emulation/docker
    • Device controller for cgroups - built-in - required by app-emulation/docker
    • Resource counters - built-in - Optional for Docker
      • Memory Resource Controller for Control Groups - built-in - for below dep
        • Memory Resource Controller Swap Extension - built-in - optional for app-emulation/docker
    • Enable perf_event per-cpu per-container group (cgroup) monitoring - built-in - optional for app-emulation/docker
    • Group CPU scheduler
      • Group scheduling for SCHED_OTHER
        • CPU bandwidth provisioning for FAIR_GROUP_SCHED - built-in - optional for app-emulation/docker
  • Initial RAM filesystem and RAM disk (initramfs/initrd) support
    • Initramfs source file(s): /usr/src/linux/initramfs/initramfs_list - Builds intramfs with the specified list
• Processor type and features
  • Linux Guest support - CHOOSE: Enable if VM kernel, off otherwise
  • Supported processor vendors
    • Support Intel processors - CHOOSE if intel processor
    • Support AMD processors - CHOOSE if amd processor
    • Support Centaur processors
  • IBM Calgary IOMMU support
  • Intel MCE features - CHOOSE if intel processor
  • Dell laptop support
  • Intel microcode loading support - CHOOSE if intel processor
• Power management and ACPI options
  • ACPI (Advanced Configuration and Power Interface) Support - built-in: Allow linux to control power
• Bus options
  • PCCard (PCMCIA/CardBus) support
• Networking support
  • Networking options
    • 802.1d Ethernet Bridging - module: required by app-emulation/docker
    • Network packet filtering framework (Netfilter)
      • Core Netfilter Configuration
        • Netfilter connection tracking support - Module: required by "IPv4 connection tracking support"
        • Netfilter Xtables support
          • "addrtype" address type match support - Module: required by app-emulation/docker
          • "conntrack" connection tracking match support - Module: required by app-emulation/docker
      • IP: Netfilter Configuration
        • IPv4 connection tracking support - Module: required by "IPv4 NAT"
        • IPv4 NAT - Module - required by app-emulation/docker
        • IP tables support
          • Packet filtering - Module: required by app-emulation/docker
          • iptables NAT suppoort
            • MASQUERADE target support - Module: required by app-emulation/docker
  • Wireless
• Device Drivers
  • Generic Driver Options
    • Automount devtmpfs at /dev, after the kernel mounted the rootfs - built-in
  • Macintosh device drivers
  • Network Device support
    • Ethernet driver suppot
      • Realtek 8169 gigabit ethernet support - CHOOSE if realtek 8169 card
    • MAC-VLAN support - module: required by app-emulation/docker
    • Virtual ethernet pair device - module: required by app-emulation/docker
  • Input device support
    • Event interface - built-in: needed for Xorg
  • Character devices
    • Support multiple instances of devpts - ON - required by app-emulation/docker
  • Graphics Support
    • Direct Rendering Manger
      • Nouveau (nVidia) cards - CHOOSE if nVidia card
  • Sound Card support
    • Advanced Linux Sound Architecture
      • HD-Audio
        • Pre-Allocated buffer size for HD-audio driver - 2048 - recommend by media-sound/pulseaudio
  • Ultra Wideband devices
  • LED Support
  • Accessibility support
  • InfiniBand support
• File Systems
  • The Extended 4 (ext4) filesystem -module: Not needed on boot
  • Reiserfs support -module: Not needed on boot
  • JFS filesystem support -module: Not needed on boot
  • XFS filesystem support -module: Not needed on boot
  • Btrfs filesystem support - built-in: btrfs used as primary filesystem
    • Btrfs POSIX Access Control Lists - built-in
    • Btrfs will run sanity tests upon loading - built-in
  • Quota support
  • Network File Systems
    • NFS client support
    • Ceph distributed file system - module: Going to be experimenting with ceph as backend
• Library routines
  • PowerPC BCJ filter decoder
  • ARM BCJ filter decoder
  • ARM-Thumb BCJ filter decoder
  • SPARC BCJ filter decoder

Building an updated kernel

• Make sure system is up to date

  • Do first half of Cookbook | Gentoo Recipes | Update Install stopping before "Clean obsolete". Since the clean will remove old kernel source.

• (Optional) If just rebuilding the existing version then backup just in case

  # Backup existing
  cd /usr/src
  # See current version
  ls -ld linux
  cp -a <CURRENT Kernel> <CURRENT Kernel>.YYYYMMDD

• Select desired kernel

  eselect kernel list
  eselect kernel set 1

• Start with current settings and update

  cd /usr/src/linux
  # Current running kernel config
  zcat /proc/config.gz > /usr/src/linux/.config
  # Accept defaults for any new kernel settings
  make oldconfig
  # Copy previous initramfs config to new kernel
  cp -a ../<PREVIOUS Kernel>/initramfs/ .

• Build and install

  KERNELVER=#.##.# based on kernel being built
  EXTENSION=YYYMMDD-##      - Set to the value of "General setup | Local version" from kernel config
  make modules_prepare
  make && make modules_install
  cp .config /boot/config-${KERNELVER}-gentoo-gnu${EXTENSION}
  cp System.map /boot/System.map-${KERNELVER}-gentoo-gnu${EXTENSION}
  cp arch/x86_64/boot/bzImage /boot/kernel-${KERNELVER}-gentoo-gnu${EXTENSION}
  grub2-mkconfig -o /boot/grub/grub.cfg
  cp -a .config ../${KERNELVER}-${EXTENSION}.config.bk