flipperdevices · alchark · Jul 1, 2026 · Jun 24, 2026 · Jun 30, 2026 · Jun 30, 2026
diff --git a/Dockerfile b/Dockerfile
@@ -22,6 +22,7 @@ RUN apt-get install -y \
     flex \
     parted \
     fdisk \
+    btrfs-progs \
     python3-dev \
     python3-libfdt \
     python3-setuptools \

diff --git a/README.md b/README.md
@@ -119,7 +119,7 @@ sudo apt install git build-essential crossbuild-essential-arm64 bc bison flex \
 For assembling disk images — debos, bmaptool, and zeekstd all need to be installed from source:
 
 ```bash
-sudo apt install golang pipx pigz cargo parted fdisk mmdebstrap \
+sudo apt install golang pipx pigz cargo parted fdisk btrfs-progs mmdebstrap \
     systemd-resolved systemd-container qemu-user-binfmt \
     libglib2.0-dev libostree-dev fakemachine
 

diff --git a/build-images.sh b/build-images.sh
@@ -23,20 +23,10 @@ trap cleanup EXIT
 
 bmaptool copy "$IMG_OUT"/debian-rootfs.img.zst "$IMG_OUT"/debian-rootfs.img
 sync "$IMG_OUT"/debian-rootfs.img
-TMP=`mktemp`
-chmod 644 "$TMP"
 
 # Boot entries are pure BLS in /boot/loader/entries, read directly by U-Boot's
 # 'bls' bootmeth (no extlinux.conf). Nothing to rewrite here for the boot menu.
 
-debugfs -R "cat /usr/lib/os-release"  "$IMG_OUT"/debian-rootfs.img > "$TMP"
-echo "BUILD_ID=$BUILD_ID" >> "$TMP"
-debugfs -w -R "rm /usr/lib/os-release" "$IMG_OUT"/debian-rootfs.img
-debugfs -w -R "write $TMP /usr/lib/os-release" "$IMG_OUT"/debian-rootfs.img
-sync "$IMG_OUT"/debian-rootfs.img
-
-rm -f "$TMP"
-
 for s in 512 4096; do
 	echo "Creating images for $s-byte sector size"
 	truncate -s "$IMGSIZE" "$TMPDIR"/debian-"$s"-nobootloader-"$BUILD_ID".img

diff --git a/debian-rk3576-img.yaml b/debian-rk3576-img.yaml
@@ -1,16 +1,23 @@
 {{ $sectorsize := or .sectorsize 512 }}
-{{ $imagesize := or .imagesize "4GiB" }}
-{{ $kerneldir := or .kerneldir "prebuilt/linux" }}
-{{ $cmdline := or .cmdline "audit=0 console=tty1 console=ttyS0,1500000n8" }}
+{{ $imagesize  := or .imagesize  "4GiB" }}
+{{ $kerneldir  := or .kerneldir  "prebuilt/linux" }}
+{{ $cmdline    := or .cmdline    "audit=0 console=tty1 console=ttyS0,1500000n8" }}
+{{ $fslabel    := or .fslabel    "flipperos" }}
+{{- /* fs-wide btrfs mount options. ssd is FORCED (loopback/eMMC isn't reliably
+       detected as non-rotational). */ -}}
+{{ $btrfsopts  := or .btrfsopts  "compress=zstd,noatime,ssd,discard=async" }}
+{{ $rootdev    := "findmnt -fn --nofsroot -o SOURCE --target $IMAGEMNTDIR" }}
 
 architecture: arm64
 sectorsize: {{ $sectorsize }}
-
 actions:
   - action: unpack
     description: Load a tarball of the root filesystem
     file: debian-ospack.tar.gz
 
+  # debos formats btrfs (default flags, random FSUUID), mounts the top level at
+  # $IMAGEMNTDIR, and records the standard root fstab line + root=UUID.
+  # fsck:false -> passno 0 (no boot-time fsck for btrfs).
   - action: image-partition
     imagename: debian-nobootloader.img
     imagesize: {{ $imagesize }}
@@ -21,17 +28,86 @@ actions:
         start: 32KiB
         end: 64MiB
       - name: root
-        fs: ext4
+        fs: btrfs
+        fslabel: {{ $fslabel }}
+        fsck: false
         start: 64MiB
         end: -1MiB
-        flags: [ boot ]
     mountpoints:
       - mountpoint: /
         partition: root
-        options: [ x-systemd.growfs ]
+        options: [ compress=zstd, noatime, ssd, discard=async, x-systemd.growfs ]
+
+  # Subvolume layout (no reformat). /boot is a TOP-LEVEL subvolume named "boot"
+  # (not "@boot") so it sits outside @ -> a single shared /boot that root snapshots
+  # never capture, and so U-Boot, which reads the default (top-level) subvolume,
+  # resolves /boot/extlinux/... straight into it. Keep the default subvolume as the
+  # top level (do NOT set-default @) or U-Boot won't see this sibling /boot.
+  - action: run
+    description: Create subvolumes and mount the layout
+    chroot: false
+    command: |
+      set -eu
+      ROOTPART="$({{ $rootdev }})"
+
+      # debos has the top level (subvolid=5) mounted here; create subvolumes on it.
+      for sv in @ boot @home @snapshots @var-log @var-cache; do
+        btrfs subvolume create "$IMAGEMNTDIR/$sv"
+      done
+      umount "$IMAGEMNTDIR"
 
+      # Mount @ at the mount point debos owns, then nest the rest under it.
+      mount -t btrfs -o "{{ $btrfsopts }},subvol=@" "$ROOTPART" "$IMAGEMNTDIR"
+      mkdir -p "$IMAGEMNTDIR/boot" \
+               "$IMAGEMNTDIR/home" \
+               "$IMAGEMNTDIR/.snapshots" \
+               "$IMAGEMNTDIR/var/log" \
+               "$IMAGEMNTDIR/var/cache"
+      mount -t btrfs -o "{{ $btrfsopts }},subvol=boot"       "$ROOTPART" "$IMAGEMNTDIR/boot"
+      # Keep /boot uncompressed so U-Boot can read the kernel/dtb/initrd regardless
+      # of whether its btrfs driver was built with zstd support. The property is
+      # stored on the subvolume and inherited by files added later (kernel updates).
+      btrfs property set "$IMAGEMNTDIR/boot" compression none
+      mount -t btrfs -o "{{ $btrfsopts }},subvol=@home"      "$ROOTPART" "$IMAGEMNTDIR/home"
+      # @snapshots is mounted only for the build (to write the Factory Image); it's
+      # not in fstab, so the .snapshots mountpoint is removed from @ before detach.
+      mount -t btrfs -o "{{ $btrfsopts }},subvol=@snapshots" "$ROOTPART" "$IMAGEMNTDIR/.snapshots"
+      mount -t btrfs -o "{{ $btrfsopts }},subvol=@var-log"   "$ROOTPART" "$IMAGEMNTDIR/var/log"
+      mount -t btrfs -o "{{ $btrfsopts }},subvol=@var-cache" "$ROOTPART" "$IMAGEMNTDIR/var/cache"
+
+  # debos writes the standard root line into /etc/fstab and root=UUID into the
+  # cmdline; the root subvolume is selected by the appended rootflags=subvol=@.
   - action: filesystem-deploy
-    append-kernel-cmdline: {{ $cmdline }}
+    append-kernel-cmdline: rootflags=subvol=@ {{ $cmdline }}
+
+  # Add fstab entries for the non-root subvolumes (debos only generated the root
+  # line). The FSUUID is read back at build time. @snapshots is intentionally
+  # omitted -- it holds the Factory Image and is mounted on demand for rollback,
+  # never auto-mounted at runtime.
+  - action: run
+    description: Append subvolume entries to /etc/fstab
+    chroot: false
+    command: |
+      set -eu
+      ROOTPART="$({{ $rootdev }})"
+      FSUUID="$(blkid -o value -s UUID -p -c none "$ROOTPART")"
+      cat >> "$IMAGEMNTDIR/etc/fstab" <<EOF
+      UUID=$FSUUID  /boot        btrfs  {{ $btrfsopts }},subvol=boot        0  0
+      UUID=$FSUUID  /home        btrfs  {{ $btrfsopts }},subvol=@home       0  0
+      UUID=$FSUUID  /var/log     btrfs  {{ $btrfsopts }},subvol=@var-log    0  0
+      UUID=$FSUUID  /var/cache   btrfs  {{ $btrfsopts }},subvol=@var-cache  0  0
+      EOF
+
+  # journald's append-heavy writes fragment badly under btrfs copy-on-write. Pre-create
+  # the journal dir with NODATACOW (chattr +C) while it's still empty, so the journal
+  # files written on first boot inherit it. (+C also implies no compression.)
+  - action: run
+    description: Disable CoW on the systemd journal directory
+    chroot: false
+    command: |
+      set -eu
+      mkdir -p "$IMAGEMNTDIR/var/log/journal"
+      chattr +C "$IMAGEMNTDIR/var/log/journal"
 
   - action: overlay
     description: Copy Linux kernel packages into the target
@@ -43,3 +119,26 @@ actions:
     description: Install Linux kernel packages inside the target
     chroot: true
     command: find /var/cache/linux-kernel -name linux-image-\*.deb -a ! -name \*-dbg_\* -print0 | xargs -0 apt install -y
+
+  # Read-only "Factory Image" snapshot of @, taken once the rootfs and kernel are
+  # fully deployed. It captures @ only -- the nested subvols (boot/home/var-*) are
+  # separate and excluded.
+  - action: run
+    description: Create the read-only Factory Image snapshot of @
+    chroot: false
+    command: btrfs subvolume snapshot -r "$IMAGEMNTDIR" "$IMAGEMNTDIR/.snapshots/@_Factory-Image"
+
+  # Unmount the nested subvolumes (deepest first), leaving @ mounted at
+  # $IMAGEMNTDIR. debos' image-partition Cleanup unmounts @ and detaches the loop;
+  # without this it would fail with EBUSY on the still-mounted children.
+  - action: run
+    description: Unmount nested subvolumes before debos detaches the loop
+    chroot: false
+    command: |
+      set -eu
+      sync
+      findmnt -rno TARGET --submounts "$IMAGEMNTDIR" \
+        | awk -v root="$IMAGEMNTDIR" '$0 != root' \
+        | awk '{ print length, $0 }' | sort -rn | cut -d" " -f2- \
+        | while read -r mp; do umount "$mp"; done
+      rmdir "$IMAGEMNTDIR/.snapshots"
diff --git a/debian-rk3576-ospack.yaml b/debian-rk3576-ospack.yaml
@@ -33,6 +33,8 @@ actions:
       - breeze-gtk-theme
       - bsdextrautils
       - bsdmainutils
+      - btrfs-compsize
+      - btrfs-progs
       - build-essential
       - cage
       - ca-certificates
@@ -43,6 +45,7 @@ actions:
       - dmidecode
       - dnsmasq-base
       - drm-info
+      - duperemove
       - gstreamer1.0-plugins-bad
       - gstreamer1.0-tools
       - e2fsprogs

diff --git a/overlays/configs/kernel/install.d/90-loaderentry.install b/overlays/configs/kernel/install.d/90-loaderentry.install
@@ -35,6 +35,19 @@ TITLE_MAX="${FLIPPER_TITLE_MAX:-26}"
 DTB_DIR="/usr/lib/linux-image-$KERNEL_VERSION"
 DTB_DIRS="$DTB_DIR /usr/lib/modules/$KERNEL_VERSION/dtb"
 
+# U-Boot reads the btrfs TOP LEVEL (subvolid 5), so in-entry devicetreedir/overlay paths must
+# be prefixed with the root subvolume the entry boots -- /@<subvol>/usr/lib/... -- where that
+# root's DTBs live (the kernel package installs them in every root's /usr/lib). The prefix is
+# derived per entry from its own rootflags=subvol= (each profile boots a different root). The
+# staged kernel/initrd live under /boot (the boot subvolume) and are never prefixed.
+# Set FDT_SUBVOL_PREFIX to override the derivation (e.g. "" if the root is not a subvolume).
+fdt_prefix() {  # $1 = options string -> "/<rootflags-subvol>" (or $FDT_SUBVOL_PREFIX if set)
+    if [ "${FDT_SUBVOL_PREFIX+x}" = x ]; then printf '%s' "$FDT_SUBVOL_PREFIX"; return 0; fi
+    _sv=$(printf '%s' "$1" | tr ' ' '\n' | sed -n 's/^rootflags=subvol=//p' | tail -n1)
+    [ -n "$_sv" ] && printf '/%s' "$_sv"
+    return 0
+}
+
 log() { [ "${KERNEL_INSTALL_VERBOSE:-0}" -gt 0 ] && echo "flipper-bls: $*" >&2; return 0; }
 die() { echo "flipper-bls: $*" >&2; exit 1; }
 trim() { printf '%s' "$1" | sed 's/^ *//; s/ *$//'; }
@@ -53,8 +66,12 @@ if [ "$COMMAND" = "remove" ]; then
 fi
 [ "$COMMAND" = "add" ] || exit 0
 
-# --- locate the boot mount, so in-entry paths are relative to the boot partition --
-[ -n "$BOOT_MNT" ] || BOOT_MNT="$(stat -c %m "$BOOT_ROOT")"
+# In-entry paths are relative to the partition U-Boot actually reads. On Flipper One
+# that is always the root partition — /boot is a directory/subvolume on it, never a
+# separate boot partition U-Boot mounts — so paths must keep the /boot prefix, i.e.
+# BOOT_MNT=/. (Override BOOT_MNT in the environment if /boot ever becomes its own
+# partition, which would make boot_rel strip the mountpoint again.)
+[ -n "$BOOT_MNT" ] || BOOT_MNT="/"
 
 # absolute path under BOOT_ROOT -> path as it must appear inside a BLS entry (relative
 # to the boot partition; identical to the absolute path when /boot is on the rootfs).
@@ -130,7 +147,7 @@ fi
 # devicetreedir (U-Boot fdtdir extension) — referenced in place, opt-in via a
 # /etc/kernel/devicetreedir file containing a true boolean. Only when no single
 # devicetree was configured.
-DEVICETREEDIR_SRC=""; DEVICETREEDIR_ENTRY=""
+DEVICETREEDIR_SRC=""; DEVICETREEDIR_REL=""
 if [ -z "$DEVICETREE" ] && [ -f "$CONF_ROOT/devicetreedir" ]; then
     _v=""; read -r _v <"$CONF_ROOT/devicetreedir" || :
     case "$_v" in
@@ -143,7 +160,7 @@ if [ -z "$DEVICETREE" ] && [ -f "$CONF_ROOT/devicetreedir" ]; then
                 [ -n "$DEVICETREEDIR_SRC" ] && break
             done
             [ -n "$DEVICETREEDIR_SRC" ] || die "no device-tree directory for $KERNEL_VERSION"
-            DEVICETREEDIR_ENTRY="$(boot_rel "$DEVICETREEDIR_SRC")"
+            DEVICETREEDIR_REL="$(boot_rel "$DEVICETREEDIR_SRC")"   # /usr/lib/...; prefixed per entry
             ;;
     esac
 fi
@@ -180,6 +197,8 @@ done
 # write_entry FILE TITLE OPTIONS FDTOVERLAYS
 write_entry() {
     _f="$1"; _title="$2"; _opts="$3"; _fdtov="$4"
+    # devicetreedir is prefixed with THIS entry's root subvol (U-Boot reads subvolid 5)
+    _dtdir=""; [ -n "$DEVICETREEDIR_REL" ] && _dtdir="$(fdt_prefix "$_opts")$DEVICETREEDIR_REL"
     {
         echo "# Boot Loader Specification type#1 entry (Flipper One)"
         echo "title      $_title"
@@ -188,21 +207,22 @@ write_entry() {
         [ -n "$SORT_KEY" ] && echo "sort-key   $SORT_KEY"
         [ -n "$_opts" ]  && echo "options    $_opts"
         echo "linux      $KERNEL_ENTRY"
-        [ -n "$DEVICETREE_ENTRY" ]    && echo "devicetree    $DEVICETREE_ENTRY"
-        [ -n "$DEVICETREEDIR_ENTRY" ] && echo "devicetreedir $DEVICETREEDIR_ENTRY"
-        [ -n "$_fdtov" ]              && echo "devicetree-overlay $_fdtov"
+        [ -n "$DEVICETREE_ENTRY" ] && echo "devicetree    $DEVICETREE_ENTRY"
+        [ -n "$_dtdir" ]           && echo "devicetreedir $_dtdir"
+        [ -n "$_fdtov" ]           && echo "devicetree-overlay $_fdtov"
         for _i in $INITRD_ENTRIES; do echo "initrd     $_i"; done
     } >"$_f"
     return 0   # don't let a trailing empty conditional's status abort `set -e`
 }
 
 # Echo the space-separated paths of the named DT overlays (flat, next to the DTBs).
 # Returns non-zero with no output if any one is missing.
-overlay_paths() {
+overlay_paths() {  # $1 = subvol prefix (e.g. /@Desktop); remaining args = overlay names
+    _pfx="$1"; shift
     _paths=""
     for _n in "$@"; do
-        [ -f "$OVERLAY_DIR/$_n.dtbo" ] || return 1
-        _paths="$_paths${_paths:+ }$OVERLAY_DIR/$_n.dtbo"
+        [ -f "$OVERLAY_DIR/$_n.dtbo" ] || return 1   # check the real on-disk path
+        _paths="$_paths${_paths:+ }$_pfx$OVERLAY_DIR/$_n.dtbo"
     done
     printf '%s' "$_paths"
 }
@@ -225,10 +245,10 @@ make_title() {
     fi
 }
 
-# Base entry == the [DEFAULT] profile.
-write_entry "$ENTRY_STEM.conf" "$(make_title '[DEFAULT]')" "$BASE_OPTS" ""
+# Base entry == the [DESKTOP] profile.
+write_entry "$ENTRY_STEM.conf" "$(make_title '[DESKTOP]')" "$BASE_OPTS" ""
 
-[ -f "$PROFILES" ] || { log "$PROFILES not found, only the [DEFAULT] entry written"; exit 0; }
+[ -f "$PROFILES" ] || { log "$PROFILES not found, only the [DESKTOP] entry written"; exit 0; }
 
 while IFS='|' read -r tok suf extra gate dtbos legend; do
     tok="$(echo "$tok" | tr -d '[:space:]')"
@@ -257,7 +277,7 @@ while IFS='|' read -r tok suf extra gate dtbos legend; do
     required=0
     case "$dtbos" in '!'*) required=1; dtbos="$(trim "${dtbos#\!}")" ;; esac
 
-    paths="$(overlay_paths $dtbos)" || paths=""
+    paths="$(overlay_paths "$(fdt_prefix "$opts")" $dtbos)" || paths=""
     if [ -z "$paths" ] && [ "$required" = 1 ]; then
         log "skip $tok (overlays not found for $KERNEL_VERSION)"
         continue