## About gentoo-install

This script performs a reasonably minimal installation of gentoo. An EFI system is highly
recommended, but legacy BIOS boot is also supported. The script supports both systemd (default)
and OpenRC as the init system. The main performed steps are:

1. Partitioning
1. Download & verify stage3 tarball
1. Extract stage3
1. Initialize portage
1. Install kernel
1. Install additional software

The system will use `sys-kernel/gentoo-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 detect and manage your kernel configuration, have a look at [autokernel](https://github.com/oddlama/autokernel).

## Quick start

Edit `scripts/config.sh` and execute `./install` in any live system.
You can review the partitioning that will be applied before anything critical is done.
Afterwards, this will apply the partitioning scheme and properly
install the selected stage3 gentoo system. The new system will by default use
`gentoo-kernel-bin` as the kernel, and an initramfs generated by dracut to provide
a bootable environment. The script can optionally install `sshd` and `ansible` to
allow for a convenient setup of the new system afterwards.

## Overview

Here is a more complete overview of what this script does:

1. Partition disks (supports gpt, raid, luks)
1. Download and cryptographically verify the newest stage3 tarball
1. Extract the stage3 tarball
1. Sync portage tree
1. Configure portage (create zz-autounmask files, configure MAKEOPTS, EMERGE_DEFAULT_OPTS)
1. Select the fastest gentoo mirrors
1. Configure the base system
1. Install git (so you can add your portage overlays later)
1. Install `sys-kernel/gentoo-kernel-bin` (until you replace it)
1. Create efibootmgr entry or install syslinux depending on whether your system uses EFI
1. Generate a basic fstab
1. Ask for a root password

Also, optionally the following will be done:

* Install sshd with secure config
* Install dhcpcd (only for OpenRC)
* 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. Have a look at the [Recommendations](#Recommendations) section.

## 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](https://www.archlinux.org/download/) live iso works fine.
2. Clone this repository
3. Edit `scripts/config.sh`, and particularily pay attention to
   the device which will be partitioned. The script will ask for confirmation
   before partitioning, but better be safe there.
4. Execute `./install`. The script will tell you if your live
   system is missing any required software.

The script should be able to run without any user supervision after partitioning, but depending
on the current state of the gentoo repository you might need to intervene in case a package fails
to emerge. The critical commands will ask you what to do in case of a failure.

### 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 the hardened nomultilib profile without systemd.

### (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 service (none by default).

The script will create a group named `sshusers`, and only users in that group will be
allowed to log in via ssh. If you have added a user for yourself, you might want
to add the user to that group. Be aware that root login is always denied.

### (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. The ansible user will be added to
the sshusers group.

### (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.

### Troubleshooting

The script checks every command for success, so if anything fails during installation,
you will be given a proper message of what went wrong. Inside the chroot,
most commands will be executed in some kind of try loop, and allow you to
fix problems interactively with a shell, to retry, or to skip the command.

## Recommendations

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

* Read the news with `eselect news read`.
* Use a custom kernel (config and hardening, see [autokernel](https://github.com/oddlama/autokernel)), and remove `gentoo-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 `FEATURES="buildpkg"` if you want to build binary packages
* Use a safe umask like `umask 0077`

## References

* [Sakaki's EFI Install Guide](https://wiki.gentoo.org/wiki/Sakaki%27s_EFI_Install_Guide)
* [Gentoo AMD64 Handbook](https://wiki.gentoo.org/wiki/Handbook:AMD64)