Table of contents

Introduction

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

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.

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 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.

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.