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gentoo-install/README.md

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Gentoo installation script

This script performs a reasonably minimal installation of gentoo for an EFI system. It does everything from the ground up, including creating partitions, downloading and extracting the stage3 archive, initial system configuration and optionally installing some additional software. The script only supports OpenRC and not systemd.

The system will temporarily use sys-kernel/vanilla-kernel-bin, which should be suitable to boot most systems out of the box. I strongly recommend you to replace this kernel with a custom built one, when the system is functional. If you are looking for a way to properly manage your kernel configuration parameters, have a look at kernconf. There you will also find information on how to select the correct options for your system, and information on kernel hardening.

Overview

Here is a quick overview of what this script does:

  • Does everything minus something
  • Partition the device (efi, optional swap, linux root)
  • Download and cryptographically verify the newest stage3 tarball
  • Extract the stage3 tarball
  • Sync portage tree
  • Configure the base system
    • Set hostname
    • Set timezone
    • Set keymap
    • Generate and select locale
    • Prepare zz-autounmask files for portage autounmasking
  • Select best 4 gentoo portage mirrors
  • Install git (so you can add your portage overlays later)
  • Install sys-kernel/vanilla-kernel-bin (temporarily, until you replace it)
  • Copy kernel to efi partition
  • Create boot entry using efibootmgr
  • Generate fstab
  • Lets you set a root password

Also, optionally the following will be done:

  • Install sshd with secure config
  • Install dhcpcd
  • Install ansible, create ansible user and add authorized ssh key
  • Install additional packages provided in config

Anything else is probably out of scope for this script, but you can obviously do anything later on when the system is booted. I highly recommend building a custom kernel and maybe encrypting your root filesystem. Have a look at the Recommendations section.

Config

The config file scripts/config.sh allows you to adjust some parameters of the installation. The most important ones will probably be the device to partition, and the stage3 tarball name to install. By default you will get hardened nomultilib

Using existing partitions

If you want to use existing partitions, you will have to set ENABLE_PARTITIONING=false. As the script uses uuids to refer to partitions, you will have to set the corresponding partition uuid variables in the config (all variables beginning with PARTITION_UUID_).

(Optional) sshd

The script can provide a fully configured ssh daemon with reasonably good security settings. It will by default only allow ed25519 keys, restrict the key exchange algorithms, disable any password based authentication, and only allow specifically mentioned users to use ssh (none by default).

To add a user to the list of allowed users, append AllowUsers myuser to /etc/ssh/sshd_config. I recommend to create a separate group for all ssh users (like sshusers) and to use AllowGroups sshusers. You should adjust this to your preferences when the system is installed.

(Optional) Ansible

This script can install ansible, create a system user for ansible and add an ssh key of you choice to the .authorized_keys file. This allows you to directly use ansible when the new system is up to configure the rest of the system.

(Optional) Additional packages

You can enter any amount of additional packages to be installed on the target system. These will simply be passed to a final emerge call before the script is done. Autounmasking will be done automatically.

Install

Installing gentoo with this script is simple.

  1. Boot into the live system of your choice. As the script requires some utilities, I recommend using a live system where you can quickly install new software. Any Arch Linux live iso works fine.
  2. Clone this repository
  3. Edit gentoo-bootstrap/scripts/config.sh, and particularily pay attention to the device which will be partitioned. The script will ask before partitioning, but better be safe than sorry.
  4. Execute bash gentoo-bootstrap/install. The script will tell you if your live system is missing any required software.

Recommendations

There are some things that you probably want to do after installing the base system, or should consider:

  • Use a custom kernel (config and hardening, see kernconf), and remove vanilla-kernel-bin
  • Adjust /etc/portage/make.conf
    • Set CFLAGS to -O2 -pipe -march=native for native builds
    • Set CPU_FLAGS_X86 using the cpuid2cpuflags tool
    • Set MAKEOPTS to -jN with N being the amount of threads used for building
    • Set EMERGE_DEFAULT_OPTS to -jN if you want parallel emerging
    • Set FEATURES="buildpkg" if you want to build binary packages
  • Use a safe umask like umask 0077
  • Edit /etc/ssh/sshd_config, change the port and create a sshusers group.
  • Encrypt your system using LUKS
    • Remount the root fs read-only
    • Use rsync -axHAWXS --numeric-ids --info=progress2 / /path/to/backup to safely backup the whole system including all extended attributes.
    • Encrypt partition with LUKS
    • Use rsync to restore the saved system root.

References