SteamOS 3/Steam Deck Btrfs converter

This injector will install the necessary payload to keep a btrfs formatted /home even through system updates. You may also choose to only install the support for formatting and mounting of multiple filesystems for the SD cards. It will allow to mount btrfs, f2fs, ext4, fat, exfat and ntfs formatted SD cards and will also force new SD cards to be formatted as btrfs by default or a user configured filesystem.

Btrfs with its transparent compression and deduplication capabilities can achieve impressive storage gains but also improve loading times because of less data being read. It also supports instant snapshotting which is very useful to roll back to a previous state.

WARNING!!!! If you decide to so, it will install a service that will attempt on the next boot to convert the ext4 /home partition into btrfs and depending on the already used storage this operation may fail or take a long time!

Make sure you have at least 10-20% free space available before attempting the conversion (df -h /home 80-90% use with at least 10-20 GiB available space)

• https://wiki.archlinux.org/title/Btrfs
• https://wiki.archlinux.org/title/F2FS

Features

• Btrfs /home conversion from ext4 (optional)
• Btrfs, f2fs, ext4, fat, exfat, ntfs formatted SD card support
• Btrfs, f2fs, ext4, fat, exfat, ntfs formating of SD card
• Progress dialog and logging during the home conversion!
• Install additional pacman packages into the rootfs automatically and persist through updates
• Survives updates and branch changes!
• Steam's downloading and temp folders as subvolumes with COW disabled
• Update check
• Non-linux filesystems (fat, exfat, ntfs) can have their compatdata folder bind mounted from the internal storage for proton support if STEAMOS_BTRFS_SDCARD_COMPATDATA_BIND_MOUNT is set (and don't forget that with fat you are restricted to a maximum of 4GB per file!)

Install

Desktop installer

Switch into Desktop mode

You can download the following easy to use .desktop installer:

CAUTION: there's not an easy way back if you proceed! Once the /home partition is converted, you can not go back to ext4 and keep your files. The original files that have been changed are backed up with the .orig extension. Keep in mind that they are specifically changed to allow for a btrfs /home. It is safe to revert to the original files if the btrfs conversion was not attempted.

Please make sure you have enough free space before attempting the conversion. At least 10-20GiB and/or 10-20% free space should usually be fine.

Double-click the downloaded file

Execute the .desktop file

Press Continue to execute and follow the instructions.

If no password has been set, you will be prompted for a new one.

CLI Installer

Configuration

Before the installation you may want to modify the Configuration options

• If it's a first time installation, edit ./files/etc/default/steamos-btrfs.
• Otherwise edit /etc/default/steamos-btrfs as it will take precedence over the local one.
• You can also supply command line arguments or environment variables to the installer

CLI Install

t="$(mktemp -d)"
curl -sSL https://gitlab.com/popsulfr/steamos-btrfs/-/archive/main/steamos-btrfs-main.tar.gz | tar -xzf - -C "$t" --strip-components=1
"$t/install.sh"
rm -rf "$t"

Once the payload is installed you can also restart the installer from the rootfs:

/usr/share/steamos-btrfs/install.sh

Command line arguments

SteamOS Btrfs
Version: 1.0.0.20221104
Usage: '/usr/share/steamos-btrfs/install.sh' [OPTION]... [rootfs dev]...
Example: '/usr/share/steamos-btrfs/install.sh' --nogui /dev/disk/by-partsets/self/rootfs

  --help                 show help
  --noninteractive       run in noninteractive mode
                         apply options from config files, env vars or defaults
                         (env var: 'NONINTERACTIVE')
                         (default: 0)
  --nogui                run without gui prompts, force text prompts
                         (env var: 'NOGUI')
                         (default: 0)
  --noautoupdate         disable automatic fetching of the latest script version when updating the system, changing channels or on version check
                         (env var: 'NOAUTOUPDATE')
                         (file flag: '/usr/share/steamos-btrfs/disableautoupdate')
                         (default: 0)
  --noconverthome        disable home conversion
                         (env var: 'NOCONVERTHOME')
                         (file flag: '/usr/share/steamos-btrfs/disableconverthome')
                         (default: 0)
  --customprompt PATH    set path to a custom prompt script or executable
                         First argument supplied is the title, second argument the message to display, third argument label for yes, fourth argument label for no, fifth argument label for cancel
                         Env var 'EPROMPT_VALUE_DEFAULT' holds the default value
                         Should return 0 if OK, 1 if not, 2 if cancelled
                         (env var: 'CUSTOMPROMPT')
                         (default: '')

Expert config options:
  --STEAMOS_BTRFS_HOME_MOUNT_OPTS OPTS             set the /home mount options to use
                                                   (env var: 'STEAMOS_BTRFS_HOME_MOUNT_OPTS')
                                                   (default: 'defaults,nofail,x-systemd.growfs,noatime,lazytime,compress-force=zstd,space_cache=v2,autodefrag,nodiscard')
  --STEAMOS_BTRFS_HOME_MOUNT_SUBVOL SUBVOL         set the /home subvolume name to use
                                                   (env var: 'STEAMOS_BTRFS_HOME_MOUNT_SUBVOL')
                                                   (default: '@')
  --STEAMOS_BTRFS_ROOTFS_PACMAN_EXTRA_PKGS PKGS    set the extra pacman packages to install
                                                   (env var: 'STEAMOS_BTRFS_ROOTFS_PACMAN_EXTRA_PKGS')
                                                   (default: '')

You can specify multiple 'rootfs dev's or none and it will default to '/dev/disk/by-partsets/self/rootfs'.
Order of priority from highest to lowest for options is: command line flags, env vars, config files ('/usr/share/steamos-btrfs/files/etc/default/steamos-btrfs', '/usr/share/steamos-btrfs/files/etc/default/steamos-btrfs', '/etc/default/steamos-btrfs'), flag files ('/usr/share/steamos-btrfs/disableconverthome', '/usr/share/steamos-btrfs/disableautoupdate').

A log file will be created at '/var/log/steamos-btrfs.log'.

Remaining issues and troubleshooting

At this point the installer should be relatively mature and robust. Once the payload is installed and the conversion was greenlit by the user, on the next boot the Steam Deck will use tmpfs as /home and attempt the btrfs conversion on the real partition. Once it reboots it should all be working fine and the /home partition converted. This configuration has been confirmed by me and others to survive through updates.

A log file is created at /var/log/steamos-btrfs.log containing the installation and the home conversion log to review the process or help with bug reports.

If the conversion of the home partition fails for any reason, the service will do its best to restore the original ext4 mount and hard mask the systemd conversion service to prevent a conversion boot loop.

Please submit the log file at /var/log/steamos-btrfs.log as new issue if that happens to you.

You'll need to explicitely unmask the service yourself if you want to attempt the conversion again:

sudo systemctl unmask steamos-convert-home-to-btrfs.service

or

sudo rm /etc/systemd/system/steamos-convert-home-to-btrfs.service

Disclaimer about mounting fat, exfat, ntfs filesystems if STEAMOS_BTRFS_SDCARD_COMPATDATA_BIND_MOUNT is set: the eject functionality in the Steam client will not work because the compatdata folder is bind mounted from the internal storage. To unmount the SD card manually execute:

sudo systemctl stop sdcard-mount@mmcblk0p1.service

Alternatively you can disable bind mounting the compatdata/ folder by setting STEAMOS_BTRFS_SDCARD_COMPATDATA_BIND_MOUNT to 0 in the Configuration options. This will prevent proton games from working.

Updating or changing config options

At any time you can rerun the installer and let it download the latest version and go through the installation again to enable the latest changes or simply apply changed settings (/usr/share/steamos-btrfs/install.sh). Disabling the home conversion won't have any effect on an already converted home partition.

At times updates may change the default config options and you may want to merge the changes with your own: Configuration options

If you don't want to be prompted while running the script you can set the NONINTERACTIVE=1 environment variable:

sudo NONINTERACTIVE=1 /usr/share/steamos-btrfs/install.sh

or as command line argument:

sudo /usr/share/steamos-btrfs/install.sh --noninteractive

You may force off the gui prompts with NOGUI=1 or --nogui, it should otherwise detect if a desktop environment is running and fallback to text prompts

NOGUI=1 /usr/share/steamos-btrfs/install.sh
/usr/share/steamos-btrfs/install.sh --nogui

Uninstall

• the underlying rootfs needs to be mounted somewhere else and the readonly mode disabled
  • sudo mount /dev/disk/by-partsets/self/rootfs /mnt
  • sudo btrfs property set /mnt ro false
• the original files are backed up next to the new files with a .orig extension so you can move them back into position
  • sudo find /mnt -type f,l -name '*.orig' -exec sh -c 'mv -vf "$1" "${1%.*}"' _ '{}' \;
• make sure to disable the conversion systemd services or it will attempt to convert /home again
  • sudo rm /mnt/usr/lib/systemd/system/*.target.wants/steamos-convert-home-to-btrfs*.service
• the /home partition will need to be force formatted back to ext4 if it has been converted to btrfs (obviously all files on it will be lost!)
  • you can edit /etc/fstab to mount /home in tmpfs for the next boot : tmpfs /home tmpfs defaults,nofail,noatime,lazytime 0 0
  • force format the real /home to ext4 : sudo mkfs.ext4 -m 0 -O casefold -F -L home /dev/disk/by-partsets/shared/home
  • change the line in /etc/fstab back to ext4 : /dev/disk/by-partsets/shared/home /home ext4 defaults,nofail,x-systemd.growfs 0 2

Mount options

Btrfs mount options

The following mount options are used by default:

• noatime,lazytime: to keep writes to a minimum
• compress-force=zstd: force zstd compression always on. zstd is smart enough to do the right thing on uncompressible data, works better and achieves better results than the normal heuristics for compression. You can set a specific compression level by appending :<level> to the type e.g.: compress-force=zstd:6. The default level is 3 and going over 6 is rarely worth it (compression/decompression complexity grows quickly after that).
• space_cache=v2: make sure the newer implementation is used
• autodefrag: small random writes are queued up for defragmentation, invests more effort during writes to achieve as much contiguous data as possible. Interesting for games where more fragmentation can lead to loading stutter.
• subvol=@: by default it will create a subvolume @ (can be changed in the config) which is used as real root of the filesystem. SD Cards formatted as btrfs will be searched for the @ subvolume or fallback to /.
• ssd_spread: attempts to allocate into bigger and aligned chunks of unused space for a potential performance boost on SD cards.
• nodiscard: disables continuous discarding of freed blocks. There's already an fstrim timer that will periodically TRIM the drives.
• commit: (not by default) the commit interval, you may achieve good results by raising it to something like 120 seconds commit=120 especially on the SD card

F2FS mount options

• noatime,lazytime: to keep writes to a minimum
• compress_algorithm=zstd: use zstd compression. You can set a specific compression level by appending :<level> to the type e.g.: compress_algorithm=zstd:6. The default level is 3 and going over 6 is rarely worth it (compression/decompression complexity grows quickly after that).
• compress_chksum: verify compressed blocks with a checksum
• atgc,gc_merge: use better garbage collector, async garbage collection

ext4 mount options

• noatime,lazytime: to keep writes to a minimum

fat mount options

Don't forget that fat formatted SD cards are limited to 4GB per file!

• noatime,lazytime: to keep writes to a minimum
• uid=1000,gid=1000: make it usable for the default deck user
• utf8=1: force utf8 support

exfat mount options

• noatime,lazytime: to keep writes to a minimum
• uid=1000,gid=1000: make it usable for the default deck user

ntfs mount options

• noatime,lazytime: to keep writes to a minimum
• uid=1000,gid=1000: make it usable for the default deck user
• big_writes: prevent splitting of write buffers into 4K chunks
• umask=0022: default bitmask of file and directories
• ignore_case: ignore character case when accessing a file (lowntfs-3g)
• windows_names: prevents names not allowed by windows

Configuration options

A configuration file is available to change various filesystem options at /etc/default/steamos-btrfs.

• STEAMOS_BTRFS_HOME_CONVERT_OPTS : the options to pass to btrfs-convert during the /home conversion. You could for instance choose a different checksumming algorithm like xxhash instead of crc32c with --checksum xxhash.
• STEAMOS_BTRFS_HOME_MOUNT_OPTS : the mount options to use for mounting the /home partition. Changing only this variable will not have any effect if the conversion is already done. /etc/fstab would need to be edited to reflect the new values and you can do this easily by running the installation script again ./install.sh (pick Convert /home again during installation).
• STEAMOS_BTRFS_HOME_MOUNT_SUBVOL : the root subvolume to use when mounting. Changing only this variable will not have any effect if the conversion is already done. A new subvolume with the desired name would need to be created and /etc/fstab would need to be edited to reflect the new values.
• STEAMOS_BTRFS_SDCARD_FORMAT_FS : allows you to specify what new blank SD cards will be formatted as. One of btrfs, f2fs, ext4.
• STEAMOS_BTRFS_SDCARD_BTRFS_MOUNT_OPTS : the btrfs mount options for btrfs formatted SD cards.
• STEAMOS_BTRFS_SDCARD_BTRFS_MOUNT_SUBVOL : the default subvolume to mount if available. It also specifies the default subvolume to create on newly formatted btrfs SD cards.
• STEAMOS_BTRFS_SDCARD_BTRFS_FORMAT_OPTS : flags to pass to mkfs.btrfs during the format.
• STEAMOS_BTRFS_SDCARD_EXT4_MOUNT_OPTS : the ext4 mount options for ext4 formatted SD cards.
• STEAMOS_BTRFS_SDCARD_EXT4_FORMAT_OPTS : flags to pass to mkfs.ext4 during the format.
• STEAMOS_BTRFS_SDCARD_F2FS_MOUNT_OPTS : the f2fs mount options for f2fs formatted SD cards.
• STEAMOS_BTRFS_SDCARD_F2FS_FORMAT_OPTS : flags to pass to mkfs.f2fs during the format.
• STEAMOS_BTRFS_SDCARD_FAT_MOUNT_OPTS : the fat mount options for fat formatted SD cards.
• STEAMOS_BTRFS_SDCARD_FAT_FORMAT_OPTS : flags to pass to mkfs.vfat during the format.
• STEAMOS_BTRFS_SDCARD_EXFAT_MOUNT_OPTS : the exfat mount options for exfat formatted SD cards.
• STEAMOS_BTRFS_SDCARD_EXFAT_FORMAT_OPTS : flags to pass to mkfs.exfat during the format. (the mkfs.exfat from exfatprogs)
• STEAMOS_BTRFS_SDCARD_NTFS_MOUNT_OPTS : the ntfs mount options for ntfs formatted SD cards.
• STEAMOS_BTRFS_SDCARD_NTFS_FORMAT_OPTS : flags to pass to mkfs.ntfs during the format.
• STEAMOS_BTRFS_SDCARD_COMPATDATA_BIND_MOUNT: toggle bind mounting the compatdata/ folder for proton support on fat, exfat, ntfs filesystems. Setting to 0 makes it possible to eject the SD card from the Steam client.
• STEAMOS_BTRFS_ROOTFS_PACMAN_EXTRA_PKGS : additional pacman packages to install into the rootfs separated by spaces (e.g.: "compsize nfs-utils wireguard-tools ..."). You can install them easily immediately by running the installation script again /usr/share/steamos-btrfs/install.sh.

If you changed the default options and want to reset them or want to benefit from updated default options you can do the following:

Delete the modified file from the upper overlay layer:

sudo rm -f /var/lib/overlays/etc/upper/default/steamos-btrfs

Refresh the overlay for /etc:

sudo mount -o remount /etc

Deduplication

Using the btrfs-dedup@ timers

The script installs a btrfs-dedup@.timer and btrfs-dedup@.service that runs a background deduplication using rmlint and duperemove once a week.

It has a configuration file at /etc/conf.d/btrfs-dedup where you can modify the behaviour. By default dedup will only run when the power adapter is connected (pause/resume on AC).

You can stop and resume the deduplication at any time, duperemove in some cases can take forever so the process is limited to 4 hours max by default.

For /home:

sudo systemctl start --no-block btrfs-dedup@home.service
sudo systemctl stop --no-block btrfs-dedup@home.service

For /run/media/mmcblk0p1 (SD card):

sudo systemctl start --no-block btrfs-dedup@run-media-mmcblk0p1.service
sudo systemctl stop --no-block btrfs-dedup@run-media-mmcblk0p1.service

For any other path you can do:

sudo systemctl start --no-block btrfs-dedup@"$(systemd-escape -p <path/to/dedup>)".service
sudo systemctl stop --no-block btrfs-dedup@"$(systemd-escape -p <path/to/dedup>)".service

Manual dedup

Using first rmlint for fast efficient file deduplication and finally duperemove for block based deduplication is the most effective way to potentially reduce disk space.

Check with compsize the used disk space before deduplication:

sudo compsize /home

First use rmlint on /home:

cd /tmp
sudo rmlint --hidden --types="duplicates" --config=sh:handler=clone --xattr /home
sudo ./rmlint.sh -d -r -k
sudo rm -r rmlint*

DISCLAIMER: in most cases running duperemove will not result in a lot of space improvements and is slow.

Then use duperemove which might take a while:

cd /tmp
[ -f /home/.duperemove.hash ] && sudo cp -a /home/.duperemove.hash duperemove.hash
sudo duperemove -r -d -h --hashfile=duperemove.hash --skip-zeroes /home
sudo cp -a duperemove.hash /home/.duperemove.hash
sudo rm duperemove.hash

Check the used disk space again:

sudo compsize /home

You can do the same for the SD card just replace /home with /run/media/mmcblk0p1.

Steam preallocation woes

SteamOS' 5.13* kernel has an issue where games downloaded through the Steam client will not achieve their most optimal compression ratio. To mitigate this, the current version attempts to replace Steam's downloading and temp folders (located in Steam/steamapps/) with btrfs subvolumes and COW disabled.

If you were already using this project or you think your games' space usage is less than ideal you may want to consider defragmenting and balancing your Steam library manually:

For the internal storage:

sudo btrfs filesystem defrag -czstd -v -r -f /home/deck/.local/share/Steam/steamapps
sudo btrfs balance start -m -v /home/deck/.local/share/Steam/steamapps

For your SD card:

sudo btrfs filesystem defrag -czstd -v -r -f /run/media/mmcblk0p1/steamapps
sudo btrfs balance start -m -v /run/media/mmcblk0p1/steamapps

TODO

• SD card/any drive btrfs conversion