functions to send btrfs diffs back to the parent (incomplete)

these hard-code paths on my local machine

the names of the generated files are also not useful

4 files changed, 291 insertions, 0 deletions

diff --git a/btrfs-functions.sh b/btrfs-functions.sh
new file mode 100644
index 0000000..3648c24
--- /dev/null
+++ b/btrfs-functions.sh
@@ -0,0 +1,137 @@
+push()
+{
+    $(ARGS_NE mnt src dst_dir)
+
+    now=$(date +%F.%H%M%S) || die
+    snap_dir=$mnt/snapshot.$now
+    prev_dir=$mnt/snapshot.prev
+
+    local BTRFS_RECEIVE_DESTINATION_PATH="$dst_dir"
+    push_helper true "$snap_dir" "$prev_dir" "$src" local_btrfs_receiver
+}
+
+push_simple()
+{
+    $(ARGS_NE mnt src dst_dir)
+    local BTRFS_RECEIVE_DESTINATION_PATH="$dst_dir"
+    push_helper false "$mnt" "$src" local_btrfs_receiver
+}
+
+sex()
+{
+    (set -x; "$@")
+}
+
+local_btrfs_receiver()
+{
+    btrfs receive "$BTRFS_RECEIVE_DESTINATION_PATH"
+}
+
+shellescape()
+{
+    if [ "$BASH_VERSION" ]; then
+        printf %q "$1"
+    else
+        bash -c 'printf %q "$1"' bash "$1"
+    fi
+}
+
+remote_btrfs_receiver()
+{
+    ssh "$BTRFS_RECEIVE_DESTINATION_HOST" -- "btrfs receive $(shellescape "$BTRFS_RECEIVE_DESTINATION_PATH")"
+}
+
+push_helper()
+{
+    $(ARGS     keep_as_prev snap_dir prev_dir src dst_pipe)
+    $(NONEMPTY keep_as_prev snap_dir          src dst_pipe)
+
+    local full_dest rw_dest
+
+    btrfs subvolume snapshot -r "$src" "$snap_dir" || die
+
+    if [ "$prev_dir" -a -d "$prev_dir" ]; then
+        btrfs send -p "$prev_dir" "$snap_dir"
+    else
+        btrfs send "$snap_dir"
+    fi | "$dst_pipe" || die
+
+    if [ "$dst_pipe" = local_btrfs_receiver ]; then
+        local dst="$BTRFS_RECEIVE_DESTINATION_PATH"
+        full_dest=$dst/$(basename "$snap_dir")
+        rw_dest=$full_dest.rw
+        btrfs subvolume snapshot "$full_dest" "$rw_dest"  || die
+        btrfs_replace_default_subvolume_with "$rw_dest"
+    fi
+
+    if $keep_as_prev && [ "$prev_dir" ]
+    then
+        # keep the pushed snapshot in order to reuse it on subsequent pushes.
+        with_dir "$prev_dir"  btrfs subvolume delete  || die
+        sex mv "$snap_dir" "$prev_dir"                || die
+    else
+        btrfs subvolume delete "$snap_dir"
+    fi
+}
+
+btrfs_mountpoint()
+{
+    $(ARGS_NE dir)
+    btrfs filesystem show -m "$dir" >/dev/null 2>&1
+}
+
+btrfs_get_mountpoint()
+{
+    $(ARGS_NE dir)
+    while [ "$dir" -a "$dir" != '.' ]; do
+        if btrfs_mountpoint "$dir"
+        then printf '%s\n' "$dir"
+             return
+        fi
+        dir=$(dirname "$dir")
+    done
+    false
+}
+
+btrfs_show_default_path()
+{
+    $(ARGS_NE mp)
+    local path
+    mp=$(btrfs_get_mountpoint "$mp") || die # TODO: fix caller?
+    btrfs_mountpoint "$mp" || die "not a mountpoint: $mp"
+    path=$(btrfs subvolume get-default "$mp"/|sed -n -e 's/.* path //p')
+    printf '%s\n' "$mp/$path"
+}
+
+btrfs_replace_default_subvolume_with()
+{
+    $(ARGS_NE new_default)
+    local old_default subvol_id
+    old_default=$(btrfs_show_default_path "$new_default") || die
+
+    [ "$new_default" = "$old_default" ] && return
+
+    subvol_id=$(btrfs_show_subvolume_id "$new_default")       || die
+    btrfs subvolume set-default "$subvol_id" "$new_default" || die
+    btrfs subvolume delete "$old_default"
+    sex mv "$new_default" "$old_default"
+}
+
+btrfs_show_subvolume_id()
+{
+    $(ARGS_NE path)
+    local result
+    result=$(btrfs subvolume show "$path" | sed -n -e 's/^[ \t]*Subvolume ID:[ \t]*//p')
+    if [ "$result" ]
+    then printf '%s\n' "$result"
+    else false
+    fi
+}
+
+with_dir()
+{
+    $(ARGS_NE d)
+    shift
+    [ -d "$d" ] || return 0
+    "$@" "$d"
+}
diff --git a/btrfs-receive-root.sh b/btrfs-receive-root.sh
new file mode 100644
index 0000000..178fd64
--- /dev/null
+++ b/btrfs-receive-root.sh
@@ -0,0 +1,37 @@
+#!/bin/sh
+
+layer_dir=/home/d/sami
+seed_file=debian-live-8.4.0-amd64-standard.btrfs
+layer_file=debian-live-8.4.0-amd64-standard.layer.$$.btrfs
+layer_size=1000
+mountpoint=layer_dest.$$
+
+disable_stdout() { exec 3>&1; exec >&2; }
+enable_stdout() { exec >&3; }
+
+with_stdout() { enable_stdout; "$@"; disable_stdout; }
+
+create_layer_filesystem()
+{
+    [ ! -e "$layer_file" ] || return
+    mkdir -p "$mountpoint"                                     &&
+    dd if=/dev/zero of="$layer_file" bs=1M count="$layer_size" &&
+    mount -o subvol=/,compress "$seed_file" "$mountpoint"      &&
+    layer_dev=$(losetup -f --show "$layer_file")               &&
+    btrfs device add "$layer_dev" "$mountpoint"                &&
+    mount -o rw,remount "$mountpoint"
+}
+
+finish()
+{
+    umount "$mountpoint" &&
+    btrfstune -S1 "$layer_file"
+}
+
+set -ex
+
+cd "$layer_dir"                         &&
+disable_stdout                          &&
+create_layer_filesystem                 &&
+with_stdout btrfs receive "$mountpoint" &&
+finish
diff --git a/btrfs-send-root.sh b/btrfs-send-root.sh
new file mode 100644
index 0000000..6152db8
--- /dev/null
+++ b/btrfs-send-root.sh
@@ -0,0 +1,42 @@
+#!/bin/sh
+. ./var.sh
+. ./btrfs-functions.sh
+
+rootfs_uuid ()
+{
+    btrfs filesystem show / | sed -ne 's/.*uuid: //p'
+}
+
+remote_btrfs_receiver()
+{
+#   ssh "$BTRFS_RECEIVE_DESTINATION_HOST" -- "sudo btrfs receive $(shellescape "$BTRFS_RECEIVE_DESTINATION_PATH")"
+    ssh "$BTRFS_RECEIVE_DESTINATION_HOST" -- "sudo sh sami/btrfs-receive-root.sh"
+}
+
+dummy_receiver()
+{
+    true
+}
+
+push_remote()
+{
+    $(ARGS_NE mnt src ssh_dst)
+
+    now=$(date +%F.%H%M%S) || die
+    snap_dir=$mnt/snapshot.$now
+    prev_dir=$mnt/SEED
+
+    case "$ssh_dst" in
+        *:*) ;;
+        *) return 1;;
+    esac
+    local BTRFS_RECEIVE_DESTINATION_PATH="${ssh_dst#*:}"
+    local BTRFS_RECEIVE_DESTINATION_HOST="${ssh_dst%%:*}"
+    push_helper false "$snap_dir" "$prev_dir" "$src" remote_btrfs_receiver
+}
+
+ssh_dst=d@fifty.local:sami/test_dest
+
+mkdir -p /mnt/rootfs || die
+mountpoint -q /mnt/rootfs || mount -o subvol=/ UUID=$(rootfs_uuid) /mnt/rootfs || die
+push_remote /mnt/rootfs / "$ssh_dst"
diff --git a/var.sh b/var.sh
new file mode 100644
index 0000000..d0c7df5
--- /dev/null
+++ b/var.sh
@@ -0,0 +1,75 @@
+die()
+{
+    if [ "$*" ]; then
+        printf 'Error: %s\n' "$*" >&2
+    else
+        echo 'Error: fatal error' >&2
+    fi
+    exit 1
+}
+
+nosex()
+{
+    case $- in
+        *x*) set +x; "$@"; set -x;;
+        *) "$@";;
+    esac
+}
+
+_nonempty()
+{
+    printf '[ "${%s}" ] || die \"mandatory parameter is empty: %s\";\n' "$1" "$1"
+}
+
+_mandatory()
+{
+    printf '[ $# -ge %d ] || die \"mandatory parameter is missing: %s\";\n' "$2" "$1"
+}
+
+_assign()
+{
+    printf 'local %s="${%d}";\n' "$1" "$2"
+}
+
+_args()
+{
+    local v i=1 check="$1" assign="$2"
+    shift
+    shift
+    for v; do
+        $assign "$v" "$i"
+        $check "$v" "$i"
+        i=$((i+1))
+    done
+}
+
+_ARGS()
+{
+    echo eval "$(_args _mandatory _assign "$@")"
+}
+
+_ARGS_NONEMPTY()
+{
+    echo eval "$(_args _nonempty _assign "$@")"
+}
+
+_ARGS_OPTIONAL()
+{
+    echo eval "$(_args : _assign "$@")"
+}
+
+_NONEMPTY()
+{
+    echo eval "$(_args _nonempty : "$@")"
+}
+
+ARGS()          { nosex _ARGS "$@"; }
+ARGS_NONEMPTY() { nosex _ARGS_NONEMPTY "$@"; }
+ARGS_OPTIONAL() { nosex _ARGS_OPTIONAL "$@"; }
+NONEMPTY()      { nosex _NONEMPTY "$@"; }
+
+ARGS_NE() { ARGS_NONEMPTY "$@"; }
+
+if [ "${0#-}" = bash ]; then
+    export -f die _nonempty _mandatory _args ARGS ARGS_NONEMPTY ARGS_OPTIONAL
+fi