This is a cheatsheet with all the instructions to perform an installation of Arch Linux using BTRFS filesystem in /
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README.md

Arch installation on a BTRFS root filesystem

This is a cheatsheet with all the instructions to perform an installation of Arch Linux using BTRFS filesystem in /

[TOC]

Laptop model

The installation has been done on a Mountain Onyx laptop.

  • Screen: 15,6" Full HD IPS Mate
  • CPU: Intel® Core™ i7 6700HQ - 4C/8T
  • RAM: 8GB DDR3L 1600 SODIMM
  • Hard Disk: SSD 240GB M.2 550MB/s
  • GPU: Nvidia GTX 960M 2GB GDDR5 + Intel i915 (Skylake)
  • UEFI

First steps

I have been following Arch Wiki Beginner's Guide. Arch ISO booted in UEFI mode using systemd-boot. It was configured a wired connection too.

Partitioning

This is the selected layout for the UEFI/GPT system:

Mount point Partition Partition type Bootable flag Size
/boot /dev/sda1 EFI System Partition Yes 512 MiB
[SWAP] /dev/sda2 Linux swap No 16 GiB
/ /dev/sda3 Linux (BTRFS) No 30 GiB
/home /dev/sda4 Linux (EXT4) No 192 GiB

After creating the partitions, it was necessary to format them. Again, I followed the guide without a problem.

IMPORTANT: I used -L option with mkfs command in order to create a label for / (arch) and /home (home) partitions. It is important because fstab and the file needed to set up systemd-boot are configured to point those labels.

BTRFS layout

The only partition formated with BTRFS was /dev/sda3, which contains the whole root system. BTRFS was selected to enable snapshots support in order to avoid any possible problem with Arch updates. Sometimes, I have experimented that certain critical package updates can break the system. If it occurs, it is a good idea to have some snapshot to rollback the entire root filesystem. tmp subvolume has been created in order to avoid the inclusion of temporal files within the snapshots of rootvol. tmp snapshots never will be created, because all the files stored within tmp are temporal. This is the layout defined:

sda3 (Volume)
|
|
- _active (Subvolume)
|    |
|    - rootvol (Subvolume - It will be the current /)
|    |
|    - tmp (Subvolume - It will be the current /tmp)
|
|
- _snapshots (Subvolume -  It will contain all the snapshots which are subvolumes too)

And these are the commands:

mkfs.btrfs -L arch /dev/sda3
mount /dev/sda3 /mnt
cd /mnt
btrfs subvolume create _active
btrfs subvolume create _active/rootvol
btrfs subvolume create _active/tmp
btrfs subvolume create _snapshots

Next, mount all the partitions (/boot included) in order to start the installation:

cd
umount /mnt
mount -o subvol=_active/rootvol /dev/sda3 /mnt
mkdir /mnt/{home,tmp,boot}
mount -o subvol=_active/tmp /dev/sda3 /mnt/tmp
mount /dev/sda1 /mnt/boot
mount /dev/sda4 /mnt/home

Installing Arch Linux

Proceed with installing Arch Linux (Installation section within Beginner's guide).

Fstab

After executing genfstab -U /mnt >> /mnt/etc/fstab to generate fstab file using UUIDs for the partitions, I edited fstab and this is the result (please note that for those partitions which have a label defined, this label has been used)

#
# /etc/fstab: static file system information
#
# <file system> <dir>   <type>  <options>       <dump>  <pass>
# /dev/sda3
LABEL=arch      /               btrfs           rw,relatime,compress=lzo,ssd,discard,autodefrag,space_cache,subvol=/_active/rootvol     0 0

# /dev/sda1
UUID=C679-F6A0          /boot           vfat            rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro    0 2

# /dev/sda3
LABEL=arch      /tmp            btrfs           rw,relatime,compress=lzo,ssd,discard,autodefrag,space_cache,subvol=/_active/tmp 0 0

# /dev/sda4
LABEL=home       /home           ext4            rw,relatime,data=ordered        0 2

# /dev/sda2
UUID=04293b56-e2f9-4d3b-aded-6baad666d5bb       none            swap            defaults        0 0

# /dev/sda3 LABEL=arch volume
LABEL=arch      /mnt/defvol             btrfs           rw,relatime,compress=lzo,ssd,discard,autodefrag,space_cache     0 0

Mkinitcpio

In order to enable BTRFS on initramfs image, I added btrfs on HOOK inside /etc/mkinitcpio.conf. Then, it was necessary to execute mkinitcpio -p linux again. If you install linux-lts kernel (Long Term Support), you will have to execute mkinitcpio -p linux-lts

Bootloader

Because this is a UEFI laptop, systemd-boot was used as a bootloader. First, it was necessary to install systemd-boot. /boot partition (/dev/sda1) was previously mounted, so it was only needed to execute bootctl install. Then, I edited /boot/loader/loader.conf. This is the final content of this file:

timeout 3
default arch-btrfs
editor 0

Then, I installed intel-ucode package because I have an Intel CPU as beginners guide says.

Please, also note that arch-btrfs (above configuration) is the file created within /boot/loader/entries and its name is arch-btrfs.conf. This is the boot entry that we need to see Arch Linux option when the laptop boots, and the content of the file is:

title   Arch Linux
linux   /vmlinuz-linux
initrd  /intel-ucode.img
initrd  /initramfs-linux.img
options root=LABEL=arch rw rootflags=subvol=_active/rootvol

The line initrd /intel-ucode.img enables Intel microcode updates (installed with intel-ucode package)

Please note that the line options root=LABEL=arch rw rootflags=subvol=_active/rootvol assumes that root partition is installed in the labeled as arch, so here it is no necessary to use PUUID, UUID or the name of the partition, only the label (using LABEL variable).

Additional packages installed

A bunch of useful packages has been installed too: tlp for energy saving and advanced power management, reflector for optimizing Arch mirrors repositories, yaourt for compiling and installing packages easily from AUR repository, snapd to install snap packages, btrfs-progs to manage BTRFS filesystem.

Finish the steps in the Wiki

And reboot!!

Automated snapshots and system updates

A very simple script has been created called upgrade-system.sh and stored within /usr/bin/upgrade-system.sh for system upgrades. Before starting the installation of the packages updated, the script creates a new snapshot. Then, pacman, yaourt and snapd are launched to upgrade the system. If something went wrong, you can restore the root filesystem using the last snapshot created. This script can be found here

Configuration files

In this folder you can find all the configuration files edited or created during the installation process.

Re-installing the system

The previous way didn't work as I expected. Because of /boot partition is independent, if you want to rollback to a previous snapshot with a different kernel installed there is a problem. I don't snapshot /boot, so there it is always the images generated for the last kernel installed. This is a problem! So I reinstalled the whole system disabling UEFI mode and enabling legacy BIOS. Then, I partitioned the system using only thre partitions: sda1 for / (inlcuidng boot partition), sda2 for swap and sda3 for home. sda1 is BTRFS, but because of the whole root system is stored there, now when I snapshot this partition, /boot is included and there is no problem with different kernel installations. I used GRUB as a boot loader.

Graphics and Optimus installation

The laptop has two graphic cards: Integrated: Intel i915 and discrete NVIDIA GTX 960M. Then, it is interesting to have optimus technology enabled and working fine. This way, NVIDIA graphics card will only be used when a game is executed, saving power and extending battery life. These are the steps followed to have this technology working on this hardware (it was a little tricky).

++Note:++ For a stable installation, it is recommended a LTS system instead of a cutting edge one. Because of this, I installed linux-lts and linux-lts-headers instead of normal kernel and nvidia-lts and bbswitch-lts from the repository.

For the graphics cards installation and Optimius:

  • Install video graphic drivers: Intel including vulkan support and bumblebee with NVIDIA

  • Install primus and lib32-primus

  • We will add three kernel boot parameters in GRUB. Edit /etc/default/grub and change GRUB_CMDLINE_LINUX_DEFAULT. The line should be like this (I have removed quiet in order to see all the details of the booting process and check that evrything is OK):

    GRUB_CMDLINE_LINUX_DEFAULT="i915.enable_rc6=0 pcie_port_pm=off acpi_osi=\"!Windows 2015\""
    

    The three kernel boot parameters added are:

    • Kernel boot parameter for Skylake i915 GPU.
    • If you are using kernel 4.8 or higher, add kernel boot parameter pcie_port_pm=off as you can see here for avoiding error "Could not insert 'nvidia': No such device"
    • Kernel boot parameter acpi_osi="!Windows 2015" for avoiding the system freezes when we enable bumblebeed.service.

    Finally, execute sudo grub-mkconfig -o /boot/grub/grub.cfg in order to rebuild grub configuration with all these changes.

  • Add modules intel_agp and i915 (intel_agp must go always before i915) as you can see here within mkinitcpio.conf in order to enable KMS during the initramfs stage. This will avoid a black screen and will prevent the system to freeze. Rebuild initramfs using mkinitcpio -p linux or mkinitcpio -p linux-lts depending on the kernel you have installed.

  • Install bbswitch for graphic cards power management: sudo pacman -S bbswitch (if you are using linux-lts or custom kernel, bbswitch-dkms is recommended)

  • For launching Steam games and use NVIDIA graphics card, open Steam --> Library --> right click on the game you want to launnch --> Set Launch Options -> Type: optirun -b primus %command%

  • For launching wine games and use NVIDIA graphics card, launch the game with env WINEPREFIX="/home/egarcia/.wine" /usr/bin/optirun -b primus wine C:\windows\command\start.exe /Unix /home/egarcia/.wine/dosdevices/c:/users/Public/Escritorio/Hearthstone.lnk. Another method is, for example to execute Battle.net with wine, execute de exe file using optirun -b primus wine "C:\Program Files (x86)\Battle.net\Battle.net.exe"

Resources

Antergos Wiki for Bumblebee, NVIDIA and Optimus

Bluetooth installation

Normally, bluetooth chipset (intel/ibt-11-5.sfi) should work out of the box, but there is a problem loading btusb kernel module. In order to make it work, it is necessary to create a script in /usr/bin called start-bluetooth.sh with this content:

#!/bin/bash
modprobe -r btusb
modprobe btusb

++Tip:++ If you want, you can create a desktop launcher and locate it within ~/.local/share/applications with this content:

[Desktop Entry]
Comment[en_US]=
Comment=
Exec=gksudo /usr/bin/start-bluetooth.sh
GenericName[en_US]=
GenericName=
Icon=preferences-system-bluetooth
MimeType=
Name[en_US]=Bluetooth
Name=Bluetooth
Path=
StartupNotify=true
Terminal=false
TerminalOptions=
Type=Application
X-DBUS-ServiceName=
X-DBUS-StartupType=
X-KDE-SubstituteUID=false
X-KDE-Username=

Problem with Docker and BTRFS

More than a problem is a caveat. If the main filesystem for root is BTRFS, docker will use BTRFS storage driver (Docker selects the storage driver automatically depending on the system's configuration when it is installed) to create and manage all the docker images, layers and volumes. It is ok, but there is a problem with snapshots. Because /var/lib/docker is created to store all this stuff in a BTRFS subvolume which is into root subvolume, all this data won't be included within the snapshots. In order to allow all this data be part of the snapshots, we will change the storage driver used by Docker. It will be used devicemapper. Please, check out this reference in order to select the proper storage driver for you. You must know that depending on the filesystem you have for root, some of the storage drivers will not be allowed.

For using devicemapper:

  • Install docker
  • Create a file called storage-driver.conf within /etc/systemd/system/docker.service.d/. If the directory downs't exist, create the directory first.
  • This is the content of storage-driver.conf
[Service]
ExecStart=
ExecStart=/usr/bin/dockerd -H fd:// --storage-driver=devicemapper
  • Create /var/lib/docker/ and disable CoW (copy on write for BTRFS):
sudo chattr +C /var/lib/docker
  • Enable and start the service
sudo systemctl enable docker.service
sudo systemctl start docker.service
  • Add your user to docker group in order to use docker command withou sudo superpowers!

Pulseaudio high battery consuption

Using Energy Information application provided by KDE Plasma, I realized that pulseaudio daemon was eating the energy of my battery in a very strange way. Then I realized that it was a bug described here. To fix this bug, it is necessary to manually force power save for the audio codec:

  • Before proceeding, in a terminal launch the following command:

    cat /sys/module/snd_hda_intel/parameters/power_save*
    

    if the result is different from:

    1
    Y
    

    then try the following commands

    echo 1 | sudo tee /sys/module/snd_hda_intel/parameters/power_save
    echo Y | sudo tee /sys/module/snd_hda_intel/parameters/power_save_controller
    pkill pulseaudio
    
  • Log out and log in again to get pulseaudio restarted.

Restructuring BTRFS Layout on Antergos or another distribution

  • I have installed Antergos (Arch-based distro easy to install and to go without too much configuration) on a PC (using BIOS legacy mode instead UEFI) that I needed to work inmediately. I used BTRFS too for the installation, but the problem is that you cannot choose the layout you want for your BTRFS volume. Instead, all the root system is installed directly in the top volume itself, but I want a more refined layout (the layout defined above) in order to manage all the snapshots in a more proper way. Because of that, I detailed all the steps I made in order to mmigrate my installation to a customize layout. Once the system is installed, reboot and open a terminal to see the structure of the BTRFS volume for /:
sudo btrfs subvolume list /
cd /

Create all the subvolumes on / except rootvol subvolume:

sudo btrfs subvolume create _active
sudo btrfs subvolume create _active/tmp
sudo btrfs subvolume create _snapshots

Now, it is necessary to make a read-write snapshot of / into _active/rootvol

sudo btrfs subvolume snapshot / /_active/rootvol

Reboot the system using Archlinux LiveCD or Antergos LiveCD. Once the system is booted, mount all the structure within /mnt using as root /_active/rootvol (in my case, / is in /dev/sda1 and /home is in /dev/sdb2):

mount -o subvol=/_active/rootvol /dev/sda1 /mnt
mount -o subvol=/_active/tmp /dev/sda1 /mnt/tmp
mount /dev/sdb2 /mnt/home

Chroot the new system:

arch-chroot /mnt /bin/bash

Add btrfs as HOOK within /etc/mkinitcpio.conf and rebuild images:

mkinitcpio -p linux

Create a new directory called defvol within /mnt

mkdir /mnt/defvol

Modify fstab to reflect the changes (remember to modify / entry and point it to /_active/rootvol. Add /tmp line too). It is interesting to add /mnt/defvol in order to mount the entire volume as it is described above too. Systemd sometimes creates /var/lib/machines subvolume so add it too. The fstab file should look like this:

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
#
UUID=238a2358-8bf6-47a9-907f-47eaece88632 /home ext4 defaults,rw,relatime,data=ordered 0 0
UUID=ce5c80f2-9edd-42f6-b920-d8ae43ac461b / btrfs defaults,rw,noatime,compress=lzo,ssd,discard,space_cache,autodefrag,inode_cache,subvol=/_active/rootvol 0 0
UUID=ce5c80f2-9edd-42f6-b920-d8ae43ac461b /tmp btrfs defaults,rw,noatime,compress=lzo,ssd,discard,space_cache,autodefrag,inode_cache,subvol=/_active/tmp 0 0
UUID=ce5c80f2-9edd-42f6-b920-d8ae43ac461b /var/lib/machines btrfs defaults,rw,noatime,compress=lzo,ssd,discard,space_cache,autodefrag,inode_cache,subvol=/var/lib/machines 0 0
UUID=ce5c80f2-9edd-42f6-b920-d8ae43ac461b /mnt/defvol btrfs defaults,rw,noatime,compress=lzo,ssd,discard,space_cache,autodefrag,inode_cache,subvol=/ 0 0
UUID=4621e43f-3b86-4fa2-9d9e-823a564572f4 swap swap defaults 0 0

Reinstall GRUB (in my case, the PC was installed in BIOS legacy mode and GRUB is installed on /dev/sda):

grub-install --target=i386-pc /dev/sda
grub-mkconfig -o /boot/grub/grub.cfg

Exit chroot and unmount everything.

exit
umount /mnt -R

Reboot. Once the system is booted, check if / is pointing to /_active/rootvol. If everything is working fine, all the files within the root of the volume can be deleted.

cd /mnt/defvol
sudo rm -rf b*
sudo rm -rf d*
sudo rm -rf e*
sudo rm -rf h*
sudo rm -rf l*
sudo rm -rf m*
sudo rm -rf o*
sudo rm -rf p*
sudo rm -rf r*
sudo rm -rf s*
sudo rm -rf t*
sudo rm -rf u*

At this point, only _active, _snapshots and var should exist within /mnt/defvol. Go to /mnt/defvol/_active/rootvol and you can safely delete _active and _snapshots:

cd /mnt/defvol/_active/rootvol
sudo rm -rf _active
sudo rm -rf _snapshots

DONE!!! :) This is the original post from I got the inspiration to do this stuff.

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