Dual boot (with Windows 10) + btrfs + grub

Install Arch Linux with the following settings.

Settings
Dual Booting	Windows 10
Filesystem	Btrfs
Boot Loader	GRUB
Disk	single-disk
Disk Encryption	false

Install Windows 10

diskpart

At first, install Windows 10.

Boot from ISO which can be downloaded from here, and choose drive to install Windows 10.

You can install with the default layout, but I recommend to use custom layout. This is because the size of the default EFI partition is 100 MB.

It is possible to manage linux and windows images in that size of partition, but some tweaks is needed, for example, compressing initramfs with xz.

In this example I will allocate 500 MB for the EFI partition.

When the following installation screen appears, press shift + F10 to open cmd.

Then, use diskpart for partitioning.

Select a disk with SELECT and convert it to GPT if necessary.

CREATE to create partitions.

Each command is explained by running help, so if you do not understand a command, you can look it up as needed.

After partitioning, exit diskpart and cmd.

Press Refresh and install Windows 10 on the primary partition.

Bypass sign-in (option)

When you see sign-in window like above, press Shift + F10 and run:

ipconfig release

It will turn off the network so that sign-in fails and you can install with a local account.

Shrink

We need to get a free disk for Linux, so we start the disk manager and shrink the disk.

After that, downloads Arch Linux ISO from here and boot.

Install Arch Linux

Change Keymaps

Change the keymap to the one you use for the installation. For a Japanese keyboard, use jp106.

loadkeys jp106

Time Settings

Execute the following command to use the NTP (Network Time Protocol).

timedatectl set-ntp true

Optimizing Mirrorlist

Optimize the mirror list using reflector to access mirror servers with fast access during installation.

pacman -Syy
pacman -S reflector # `python` might be required
reflector -c Japan --sort rate -a 6 --save /etc/pacman.d/mirrorlist

The meaning of the reflector option is as follows.

Options	Description
-c Japan	Restrict mirrors to selected countries.
--sort rate	Sort by download rate.
-a 6	Restrict to servers synchronized within 6 hours.
--save /etc/pacman.d/mirrorlist	Save the mirror list to the specified path.

Disk Partitioning and Formatting

We will assume that the partition in /dev/sda is as follows.

sda
├─sda1 <-- EFI Partition
├─sda2 <-- MSR
├─sda3 <-- Windows
└─sda4 <-- Empty Partition for Linux

First, update the partition table so that the empty partition you created is used as Linux Filesystem.

gdisk /dev/sda

Format the Linux filesystem partition with BTRFS, create a subvolume, and mount it.

mkfs.btrfs /dev/sda4
mount /dev/sda4 /mnt
btrfs su cr /mnt/@
btrfs su cr /mnt/@home
btrfs su cr /mnt/@snapshots
btrfs su cr /mnt/@var_log
umount /mnt
mount -o noatime,compress=zstd,space_cache=v2,subvol=@ /dev/sda4 /mnt
mkdir -p /mnt/{boot,home,.snapshots,var/log}
mount -o noatime,compress=zstd,space_cache=v2,subvol=@home /dev/sda4 /mnt/home
mount -o noatime,compress=zstd,space_cache=v2,subvol=@snapshots /dev/sda4 /mnt/.snapshots
mount -o noatime,compress=zstd,space_cache=v2,subvol=@var_log /dev/sda4 /mnt/var/log
mount /dev/sda4 /mnt/boot

Base install

Install the package in the root directory, /mnt.

Intel

pacstrap /mnt base linux linux-firmware vim intel-ucode

AMD

pacstrap /mnt base linux linux-firmware vim amd-ucode

fstab

Generate the fstab file, which holds the information about which device to mount.

genfstab -U /mnt >> /mnt/etc/fstab

Change the Root Directory

Use chroot to set /mnt as the root directory.

arch-chroot /mnt

Localization

Create a symbolic link to /etc/localtime to change the time zone.

ln -sf /usr/share/zoneinfo/Asia/Tokyo /etc/localtime

Set the hardware clock to the current system clock. The system clock is the clock managed by the OS, and the hardware clock is the clock managed by the motherboard (hardware). when the OS is rebooted, the system clock stored in memory is lost, so the time is obtained from the hardware clock.

hwclock --systohc

To set the locale, first generate the locale. Uncomment the entries you want to use in /etc/locale.gen and run locale-gen.

vim /etc/locale.gen

- # en_US.UTF-8 UTF-8
+ en_US.UTF-8 UTF-8

locale-gen

Execute the following command to set the locale of the system.

echo LANG=en_US.UTF-8 >> /etc/locale.conf
echo KEYMAP=jp106 >> /etc/vconsole.conf

Hostname

Register hostname in /etc/hostname.

vim /etc/hostname

+ arch

Edit /etc/hosts and set IP address corresponding to hostname.

vim /etc/hosts

+ 127.0.0.1   localhost
+ ::1         localhost
+ 127.0.1.1   arch.localdomain    arch

Root Password

Set the password of root user.

passwd

Install Additional Packages

pacman -S grub efibootmgr networkmanager network-manager-applet \
 dialog os-prober mtools dosfstools base-devel linux-headers snapper \
 reflector cron git xdg-utils xdg-user-dirs ntfs-3g

Configuring mkinitcpio

Change the configurations, and reflect the changes with mkinitcpio.

vim /etc/mkinitcpio.conf

- MODULES=()
+ MODULES=(btrfs)

mkinitcpio -p linux

Bootloader

Install Grub and create config file.

grub-install --target=x86_64-efi --efi-directory=/boot --bootloader-id=GRUB
grub-mkconfig -o /boot/grub/grub.cfg

Systemd

Enables NetworkManager.

systemctl enable NetworkManager

Enables Bluetooth.

systemctl enable bluetooth

Enables reflector. The execution options are written in /etc/xdg/reflector/reflector.conf.

systemctl enable reflector.service  # update mirrorlist every boot

systemctl enable reflector.timer    # update mirrorlist weekly

Add User

Add user with useradd and set the password.

useradd -mG wheel mori
passwd mori

Give the user priviledges.

EDITOR=vim visudo

- # %wheel ALL=(ALL) ALL
+ %wheel ALL=(ALL) ALL

Reboot

exit
umount -a
reboot

Trouble shooting

• Boot entry for windows disappears from grub boot loader
  • Add GRUB_DISABLE_OS_PROBER=false to /etc/default/grub and recreate grub.cfg
  • The problem is deactivated os-prober. os-prober automatically finds operating systems and adds their boot entry, but sometimes it is deactivated. The option reactivate os-prober.