4 files changed, 57 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index 2389535..1ed07ed 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,9 @@ samizdat-pinentry: src/samizdat-pinentry.c
 wait_for_files: src/wait_for_files.c
         $(CC) $(CFLAGS)  $< -o $@
 
-bin_programs=$(addprefix src/, xorriso-usb.sh btrfs-functions.sh btrfs-receive-root.sh btrfs-send-root.sh var.sh grub-efi.sh keygen.sh initrd.sh qemu.sh btarfs dnsmasq-dhcp-script.sh samizdat-password-agent samizdat-gpg-agent publish-ip.sh) samizdat-paths.sh ${cc_files}
+bin_programs=$(addprefix src/, xorriso-usb.sh btrfs-functions.sh btrfs-receive-root.sh btrfs-send-root.sh var.sh grub-efi.sh keygen.sh initrd.sh qemu.sh dnsmasq-dhcp-script.sh samizdat-password-agent samizdat-gpg-agent publish-ip.sh) samizdat-paths.sh ${cc_files} ${btrfs_utils}
+
+btrfs_utils=$(addprefix src/btrfs-utils/, btarfs btrfs-shrink with-btrfs-seed)
 
 initrd_files:=$(wildcard src/initrd/*) dynmenu samizdat-pinentry wait_for_files
 initramfs_conf_files:=$(wildcard initramfs-tools/*)
diff --git a/src/btarfs b/src/btrfs-utils/btarfs
index a51b2ef..a51b2ef 100755
--- a/src/btarfs
+++ b/src/btrfs-utils/btarfs
diff --git a/src/btrfs-utils/btrfs-shrink b/src/btrfs-utils/btrfs-shrink
new file mode 100755
index 0000000..f3dbbb0
--- /dev/null
+++ b/src/btrfs-utils/btrfs-shrink
@@ -0,0 +1,52 @@
+#!/bin/sh
+
+die() { printf "%s: Error: %s\n" "$0" "$*" >&2; exit 1; }
+
+[ "$(id -u)" = 0 ] || die 'you are not root'
+
+shrink()
+{
+    shrinkmegs=100
+    while true; do
+        while ! btrfs filesystem resize -${shrinkmegs}M "$mountpoint"/; do
+            shrinkmegs=$((shrinkmegs - 10 ))
+            if [ $shrinkmegs -lt 10 ]; then
+                return
+            fi
+        done
+    done
+}
+
+btrfs_truncate()
+{
+    local img="$1" bytes
+    bytes=$(file "$img" | sed -ne 's?.*/\([0-9]*\)/[0-9]* bytes used.*?\1?p')
+#   548044800/1176715264 bytes used
+    if [ "$bytes" ]; then
+        truncate -s "$bytes" "$img"
+    fi
+}
+
+main()
+{
+    if [ -d "$1" ]; then
+        mountpoint -q "$1" || die "not a mountpoint: $1"
+        shrink "$1"
+    elif [ -f "$1" ]; then
+        mkdir "$1".mnt.tmp
+        mount -t btrfs "$1" "$1".mnt.tmp
+        result=$?
+        if [ $result = 0 ]; then
+            shrink "$1".mnt.tmp
+            result=$?
+        fi
+        umount "$1".mnt.tmp
+        rmdir "$1".mnt.tmp
+        btrfs_truncate "$1"
+        return $result
+    else
+        die "not a file or directory: $1"
+    fi
+}
+
+main "$@"
diff --git a/src/with-btrfs-seed b/src/btrfs-utils/with-btrfs-seed
index f78417b..637af5a 100755
--- a/src/with-btrfs-seed
+++ b/src/btrfs-utils/with-btrfs-seed
@@ -79,7 +79,7 @@ main()
 [ $# = 0 ] && usage 0
 
 CHROOT=y
-eval set -- "$(getopt -o '' --long no-chroot,resize:,fork:,btrfs-options: -n "$0" -- "$@")" || error 'getopt error'
+eval set -- "$(getopt -o '' --long shrink,no-chroot,resize:,fork:,btrfs-options: -n "$0" -- "$@")" || error 'getopt error'
 while [ $# -gt 0 ]; do
     case "$1" in
         --) shift; break;;
@@ -87,6 +87,7 @@ while [ $# -gt 0 ]; do
         --fork) FORK=$2; shift 2;;
         --btrfs-options) BTRFS_OPTIONS=$2; shift 2;;
         --no-chroot) CHROOT=; shift;;
+        --shrink) SHRINK=y; shift;;
         *) error "unrecognized option: $1"
     esac
 done