{
	"title": "Arch Linux installation",
	"subtitle": "Installation guide for the Arch Linux operating system"
}

#### Introduction

This article describes how to install [Arch Linux][1]. It is based on the
[official installation guide][2].

This primary documentation does not describe one specific installation option
but instead points out the different options the user has like selecting
bootloaders, boot modes or filesystems.

As a complement this article documents one specific installation inside a QEMU
virtual machine (VM). It might be used as a VM or converted to a binary image
file which can be written to a physical drive like an USB stick or SSD.

#### Design decisions

The installation is based on the following design decisions.

- MBR-based partition table and BIOS / legacy boot
- full disc encryption
- Btrfs filesystem
- only a minimalistic set of installed packages (no graphical environment)

Those might change in the future. A GPT-based partition table and a UEFI boot
based on a unified kernel image would be appreciated to support secure boot but
could not be achieved so far.

#### Installation

First a virtual drive is created as a file as a starting point for the VM
installation.

```
qemu-img create -f qcow2 archlinux.qcow2 8G
```

It is expected that the Arch Linux `*.iso` installation image is downloaded,
verified and saved in the same folder. See the [download page][3] for details.

The installation image can be booted with `qemu-system-x86_64`. The just
created virtual machine disk is attached as an additional drive.

```
qemu-system-x86_64 \
    -enable-kvm \
    -m 4G \
    -nic user,model=virtio \
    -drive file=archlinux.qcow2,media=disk,if=virtio \
    -smp cpus=4 \
    -nographic \
    -boot order=d \
    -cdrom archlinux-*.iso
```

On the first screen of the bootloader it needs to be specified that only the
serial console should be used which is mapped to the host terminal. For that
purpose the text below has to be typed before the bootloader picks the default
options.

```
<TAB> console=ttyS0
```

This is annoying but worth it since it allows to copy and paste all subsequent
commands instead of typing them by hand.

After specifying the console the installation image should boot. Next the user
`root` without password is used to log in.

The following command allows to check if the time is properly synchronized.

```
timedatectl
```

The virtual machine disk can be partitioned with `parted`.

```
parted /dev/vda --script mklabel msdos
parted /dev/vda --script mkpart primary fat32 1MiB 2GiB
parted /dev/vda --script mkpart primary 2GiB 100%
parted /dev/vda --script set 1 boot on
```

The following commands format the second partition for use with Linux Unified
Key Setup (LUKS) and opens this LUKS partition to open the encrypted partition
inside. The interactive questions have to be answered.

```
cryptsetup luksFormat --batch-mode --label CRYPTO_ROOT /dev/vda2
cryptsetup open /dev/vda2 root
```

The actual filesystems are then created with `mkfs`. For the `BOOT` partition
a FAT filesystem is used. The `ROOT` filesystem containing the operating
system and user data is formatted with
[BTRFS](https://btrfs.readthedocs.io/en/latest/).

```
mkfs.vfat -n BOOT /dev/vda1
mkfs.btrfs -L ROOT /dev/mapper/root
```

These two filesystems are opened by mounting them to the current system under
the path `/mnt`.

```
mount /dev/mapper/root /mnt
mount --mkdir /dev/vda1 /mnt/boot
```

The software `reflector` is executed to find appropriate Arch Linux package
servers which provide a good bandwidth at the current location. These server
references are later copied to the installed system.

```
systemctl start reflector
```

Selected software packages are installed to the new system with `pacstrap`.

```
pacstrap -K /mnt \
    base \
    linux \
    linux-firmware \
    parted \
    syslinux \
    btrfs-progs \
    networkmanager \
    chrony \
    nano \
    htop \
    openssh \
    man-db \
    man-pages \
    texinfo
```

The filesystem table (`fstab`) is created, printed and saved to the new system
to describe which filesystems should be mounted where during boot.

```
genfstab -L /mnt | tee /mnt/etc/fstab
```

Without actual booting a change root (`chroot`) command is used to use the new
system already.

```
arch-chroot /mnt
```

Miscellaneous settings are configured via the command line.

```
ln -sf /usr/share/zoneinfo/Europe/Berlin /etc/localtime
hwclock --systohc
sed -i 's/#en_US.UTF-8 UTF-8/en_US.UTF-8 UTF-8/g' /etc/locale.gen
locale-gen
echo 'LANG=en_US.UTF-8' > /etc/locale.conf
echo 'archlinux' > /etc/hostname
echo 'root' | passwd -s
systemctl enable NetworkManager
systemctl enable chronyd
```

The `syslinux` bootloader is installed and configured.

```
mkdir -p /boot/syslinux
cp /usr/lib/syslinux/bios/*.c32 /boot/syslinux/
extlinux --install /boot/syslinux
dd bs=440 count=1 conv=notrunc if=/usr/lib/syslinux/bios/mbr.bin of=/dev/vda
cp /usr/share/syslinux/syslinux.cfg /boot/syslinux/
sed -i 's|root=/dev/sda3 rw|cryptdevice=/dev/disk/by-label/CRYPTO_ROOT:root root=/dev/mapper/root rw|g' /boot/syslinux/syslinux.cfg
```

The initial RAM filesystem (`initramfs`) is configured and created to ensure
BTRFS and LUKS support during an early boot stage.

```
sed -i 's/^HOOKS.*$/HOOKS=(base udev autodetect microcode modconf kms keyboard keymap consolefont block encrypt btrfs filesystems fsck)/g' /etc/mkinitcpio.conf
mkinitcpio -P
```

The `chroot` is exited and the live system is powered off.

```
exit
poweroff
```

Optionally the QEMU image can be converted to a binary image to flash it to a
physical drive like an USB stick or SSD.

```
qemu-img convert -f qcow2 -O raw archlinux.qcow2 archlinux.img
```

This image can be written to the target device (`/dev/sdb` in this case). It is
very important to select the correct target and triple-check the following
command before execution. If the currently used system is the target it is
simply overwritten without any way back!

```
dd if=archlinux.img of=/dev/sdb bs=512 status=progress
```

Otherwise the virtual machine image can be started again with QEMU without the
installation image:

```
qemu-system-x86_64 \
    -enable-kvm \
    -m 4G \
    -nic user,model=virtio \
    -drive file=archlinux.qcow2,media=disk,if=virtio \
    -smp cpus=4
```

The username and password is based on this guide `root`. Using it with the
`-nographic` option is not yet possible.

If the new system is booted the second partition containing the LUKS container
and `ROOT` BTRFS partition can be extended to the full possible size.

```
parted /dev/sdb --script resizepart 2 100%
cryptsetup resize root
btrfs filesystem resize max /
```

With this step the installation is finished.

[1]: https://archlinux.org/
[2]: https://wiki.archlinux.org/title/Installation_guide
[3]: https://archlinux.org/download/