diff --git a/btv b/btv
index 206c75c..d75727f 100755
--- a/btv
+++ b/btv
@@ -8,14 +8,9 @@ import datetime
 import json
 import os
 import shlex
-import shutil
 import sys
-import time
-import socket
-import urllib.request
 
 CONFIG = "/etc/btv/config.ini"
-LOCKFILE = "/run/lock/btv/serialization.lock"
 
 # ------------------------------------------------------------------------------
 # Global
@@ -38,20 +33,6 @@ def chdir(new_dir):
 	finally:
 		os.chdir(previous_dir)
 
-@contextmanager
-def lockfile(path):
-	d = os.path.dirname(path)
-	
-	if not os.path.exists(d):
-		os.makedirs(d)
-	
-	f = open(path, "w")
-	
-	try:
-		yield
-	finally:
-		os.remove(path)
-
 # ------------------------------------------------------------------------------
 # Functions
 
@@ -191,17 +172,15 @@ def serialize(snap, outdir, key, snap_from=None):
 	
 	Snap and snap_from are Snapshot objects.
 	
-	A lockfile is kept for the duration of the process.
-	
 	Returns 0 on success.
 	"""
 	
 	## prepare directories
 	##
 	if snap_from:
-		name = "%s to %s" %(snap_from.name, snap.name)
+		name = "%s diff from %s" %(snap.name, snap_from.name)
 	else:
-		name = snap.name
+		name = "%s full" %(snap.name)
 	
 	directory = os.path.join(outdir, name)
 	os.makedirs(directory)
@@ -217,67 +196,52 @@ def serialize(snap, outdir, key, snap_from=None):
 			
 			return 1
 	
-	## serialization (most expensive)
+	## serialize each subvolume or subvolume pair
 	##
-	with lockfile(LOCKFILE):
-
-		for subvolume in snap.subvolumes:
-			if snap_from:
-				btrfs_send = 'btrfs send -p "%s" "%s"' %(
-					os.path.join(snap_from.path, subvolume),
-					os.path.join(snap.path, subvolume)
-				)
-			else:
-				btrfs_send = 'btrfs send "%s"' %(
-					os.path.join(snap.path, subvolume)
-				)
-			
-			error = os.system('%s | zstd | openssl enc -e -aes-256-cbc -pbkdf2 -salt -pass "file:%s" | hash-pipe sha512 "%s.btrfs.zst.aes" "%s/manifest.sha512" > "%s.btrfs.zst.aes"' %(
-				btrfs_send,
-				cfg.get("crypto", "keyfile"),
-				subvolume,
-				directory,
-				os.path.join(directory, subvolume)
-			))
-			
-			if error:
-				print(" !! failed to serialize %s" %(subvolume))
-				return error
+	for subvolume in snap.subvolumes:
+		if snap_from:
+			btrfs_send = 'btrfs send -p "%s" "%s"' %(
+				os.path.join(snap_from.path, subvolume),
+				os.path.join(snap.path, subvolume)
+			)
+		else:
+			btrfs_send = 'btrfs send "%s"' %(
+				os.path.join(snap.path, subvolume)
+			)
+		
+		error = os.system('%s | zstd | openssl enc -e -aes-256-cbc -pbkdf2 -salt -pass "file:%s" > "%s.btrfs.zst.aes"' %(
+			btrfs_send,
+			cfg.get("crypto", "keyfile"),
+			os.path.join(directory, subvolume)
+		))
+		
+		if error:
+			print(" !! failed to serialize %s" %(subvolume))
+			return error
 	
-	## final touches
-	##
+	## calculate checksums and add a self-check executable
+	## FIXME calculate this on the fly, re-reading is expensive
+	previous_wd = os.getcwd()
+	os.chdir(directory)
+	os.system('sha512sum "%s" > manifest.sha512' %(
+		'" "'.join("%s.btrfs.zst.aes" %(s) for s in snap.subvolumes)
+	))
 	
-	## add self-check and unpack executables
-	with open(os.path.join(directory, "check-integrity.sh"), "w") as f:
+	with open("check-integrity.sh", "w") as f:
 		f.write("#! /bin/sh\n\nsha512sum --check manifest.sha512\n")
-		os.chmod(f.name, 0o500)
-	
-	unpack_path = os.path.join(directory, "unpack.sh")
-	shutil.copy("/usr/share/btv/unpack.sh", unpack_path)
-	os.chmod(unpack_path, 0o500)
 	
 	## fix permissions and ownership of created objects
+	os.chmod("check-integrity.sh", 0o555)
+	
 	outdir_stat = os.stat(outdir)
 	os.chown(directory, outdir_stat.st_uid, outdir_stat.st_gid)
-	os.chmod(directory, 0o700)
 	
 	for file in os.listdir(directory):
 		path = os.path.join(directory, file)
 		os.chown(path, outdir_stat.st_uid, outdir_stat.st_gid)
-		
-		if path.endswith(".aes") or path.endswith(".sha512"):
-			os.chmod(path, 0o400)
-		
-		
 	
 	return 0
 
-def ping(url):
-	try:
-		urllib.request.urlopen(url, timeout=10)
-	except socket.error as e:
-		print("Ping failed: %s" %(e))
-
 # ------------------------------------------------------------------------------
 # Verbs
 
@@ -297,37 +261,30 @@ def do_create(args):
 	
 	## determine the rank of the new snapshot
 	##
-	if "--rank2" in args:
-		snapshot.rank = 2
-	else:
-		snaps_since_rank_1 = 1
-		snaps_since_rank_2 = 1
-		
-		for snap in list_snapshots():
-			if snap.rank == 1:
-				snaps_since_rank_1 = 1
-			else:
-				snaps_since_rank_1 += 1
-			
-			if snap.rank == 2:
-				snaps_since_rank_1 = 1
-				snaps_since_rank_2 = 1
-			else:
-				snaps_since_rank_2 += 1
-		
-		## promote the snapshot
-		if snaps_since_rank_2 >= cfg.getint("snap", "rank_2_interval"):
-			if "--process" in args:
-				snapshot.rank = 2
-			else:
-				print("!!! Rank 2 snapshot is due, please enable --process")
-				snapshot.rank = 1
-		elif snaps_since_rank_1 >= cfg.getint("snap", "rank_1_interval"):
-			snapshot.rank = 1
+	snaps_since_rank_1 = 1
+	snaps_since_rank_2 = 1
 	
-	ping_url = cfg.get("monitoring", "rank2_start_url")
-	if snapshot.rank == 2 and ping_url:
-		ping(ping_url)
+	for snap in list_snapshots():
+		if snap.rank == 1:
+			snaps_since_rank_1 = 1
+		else:
+			snaps_since_rank_1 += 1
+		
+		if snap.rank == 2:
+			snaps_since_rank_1 = 1
+			snaps_since_rank_2 = 1
+		else:
+			snaps_since_rank_2 += 1
+	
+	## promote the snapshot
+	if snaps_since_rank_2 >= cfg.getint("snap", "rank_2_interval"):
+		if "--process" in args:
+			snapshot.rank = 2
+		else:
+			print("!!! Rank 2 snapshot is due, please enable --process")
+			snapshot.rank = 1
+	elif snaps_since_rank_1 >= cfg.getint("snap", "rank_1_interval"):
+		snapshot.rank = 1
 	
 	## create the snapshot itself
 	##
@@ -350,6 +307,7 @@ def do_create(args):
 	## do optional processing
 	##
 	if snapshot.rank == 2:
+		
 		## snapshot serialization
 		# if there's a previous Rank 2 snapshot, compute a diff against it
 		# if not or if the process fails, demote this snap to Rank 1
@@ -373,18 +331,14 @@ def do_create(args):
 		else:
 			print("!!! no previous Rank 2 snapshot, please create one using btv stream")
 			snapshot.rank = 1
+		
+		## garbage collection
+		do_gc()
 	
 	## save all snapshot metadata
 	snapshot.dump()
 	
 	print(">>> Snapshot created: rank %d %s" %(snapshot.rank, snapshot.name))
-	
-	## garbage collection
-	do_gc()
-	
-	ping_url = cfg.get("monitoring", "rank2_end_url")
-	if snapshot.rank == 2 and ping_url:
-		ping(ping_url)
 
 def do_list(args):
 	"""
@@ -426,151 +380,59 @@ def do_drop(args):
 
 def do_stream(args):
 	"""
-	args are either
+	Stream the snapshot args[0] into dir args[1].
 	
-	  "diff" SNAPSHOT_FROM SNAPSHOT_TO OUTPUT_DIR
-	
-	or
-	
-	  "full" SNAPSHOT OUTPUT_DIR
-	
-	SNAPSHOT_FROM must be Rank 2.
-	
-	Streams the full or diff snapshot into OUTPUT_DIR.
-	
-	The SNAPSHOT or SNAPSHOT_TO is then promoted to Rank 2.
+	The affected snapshot is then promoted to Rank 2.
 	"""
 	
-	## args interpretation and validation
-	##
-	if not args:
-		raise UsageError("no args")
+	snapshot = get_snapshot_by_name(args[0])
 	
-	if args[0] == "diff":
-		if len(args) != 4:
-			raise UsageError("'stream diff' requires exactly 3 arguments")
-		
-		snap_from_name, snap_name, output_dir = args[1:]
-		snap_from = get_snapshot_by_name(snap_from_name)
-		
-		if not snap_from:
-			print("!!! %s is not a snapshot" %(snap_from_name))
-			sys.exit(2)
-		
-		if snap_from.rank != 2:
-			print("!!! source snapshot must be Rank 2, %s is %d" %(snap_from.name, snap_from.rank))
-			print('  > Hint: btv stream full %s "%s"' %(snap_from.name, output_dir))
-			sys.exit(3)
-	
-	elif args[0] == "full":
-		if len(args) != 3:
-			raise UsageError("'stream full' requires exactly 2 arguments")
-		
-		snap_name, output_dir = args[1:]
-		snap_from = None
-	
-	else:
-		raise UsageError("'stream' type is either 'full' or 'diff'")
-	
-	snap = get_snapshot_by_name(snap_name)
-	
-	if not snap:
-		print("!!! %s is not a snapshot" %(snap_name))
+	if not snapshot:
+		print("!!! %s is not a snapshot" %(args[0]))
 		sys.exit(2)
 	
-	if not os.path.isdir(output_dir):
-		print("!!! %s is not a directory" %(output_dir))
+	directory = args[1]
+	
+	if not os.path.isdir(directory):
+		print("!!! %s is not a directory" %(directory))
 		sys.exit(2)
 	
-	if snap_from and snap_from.name >= snap.name:
-		print("!!! source snapshot is younger than target snapshot")
-		sys.exit(3)
-	
-	## serialization work
-	##
-	if snap_from:
-		comment = "diff %s -> %s" %(snap_from.name, snap.name)
-	else:
-		comment = "full %s" %(snap.name)
-	
-	print(">>> Serializing %s into %s" %(comment, output_dir))
+	print(">>> Serializing %s into %s" %(snapshot.name, directory))
 	
 	error = serialize(
-		snap,
-		output_dir,
-		cfg.get("crypto", "keyfile"),
-		snap_from
+		snapshot,
+		directory,
+		cfg.get("crypto", "keyfile")
 	)
 	
 	if error:
 		print("!!! serialization failed")
 	else:
-		snap.rank = 2
-		snap.notes.add("manually streamed")
+		snapshot.rank = 2
+		snapshot.notes.add("fully streamed")
+		snapshot.dump()
 		
-		if not snap_from:
-			snap.notes.add("fully streamed")
-		snap.dump()
-		
-		print("<<< %s serialized and promoted to Rank 2" %(snap.name))
+		print("<<< %s serialized and promoted to Rank %d" %(snapshot.name, snapshot.rank))
 
 def do_gc(args=None):
 	"""
 	Drops old snapshots.
-	
-	If the only arg is "greedy", drops ALL snapshots except the youngest
-	Rank 2. If it's a number, drops that many oldest snapshots.
 	"""
 	
-	if args: 
-		if args[0] == "greedy":
-			newest = list_snapshots(2)[-1]
-			
-			if newest:
-				print(">>> Dropping all snapshots except the newest Rank 2 in 5 s...")
-				time.sleep(5)
-				
-				for snap in list_snapshots():
-					if snap.name != newest.name:
-						snap.drop()
-			
-			else:
-				print("!!! no Rank 2 snapshot exists")
-				sys.exit(1)
-		
-		else:
-			try:
-				count = int(args[0])
-			except ValueError:
-				print("!!! %s is not a count of snapshots to delete" %(args[0]))
-				sys.exit(1)
-			
-			snaps = list_snapshots()[:count]
-			
-			for snap in snaps:
-				print("   %d %s %s" %(snap.rank, snap.name, ", ".join(snap.notes)))
-			
-			print(">>> These snapshots will be dropped in 5 s...")
-			time.sleep(5)
-			
-			for snap in snaps:
-				snap.drop()
+	counts = [0, 0, 0] # Rank 0, 1, 2
+	limits = [
+		cfg.getint("gc", "rank_0_count"),
+		cfg.getint("gc", "rank_1_count"),
+		cfg.getint("gc", "rank_2_count")
+	]
 	
-	else:
-		counts = [0, 0, 0] # Rank 0, 1, 2
-		limits = [
-			cfg.getint("gc", "rank_0_count"),
-			cfg.getint("gc", "rank_1_count"),
-			cfg.getint("gc", "rank_2_count")
-		]
+	for snap in reversed(list_snapshots()):
+		counts[snap.rank] += 1
 		
-		for snap in reversed(list_snapshots()):
-			counts[snap.rank] += 1
+		if counts[snap.rank] > limits[snap.rank]:
+			print(" >> delete Rank %d %s" %(snap.rank, snap.name))
 			
-			if counts[snap.rank] > limits[snap.rank]:
-				print(" >> delete Rank %d %s" %(snap.rank, snap.name))
-				
-				snap.drop()
+			snap.drop()
 
 verb_router = {
 	"snapshot": do_create,
@@ -588,17 +450,12 @@ def print_help():
   {cmd} VERB [args]
 
 Verbs:
-  snapshot [--process] [--rank2]
-    Create a snapshot. If --process is passed, do all optional work. If
-    --rank2 is passed, the new snapshot is automatically promoted to Rank 2
-    and --process is implied.
+  snapshot [--process]
+    Create a snapshot. If --process is passed, do all optional work.
   
-  stream full SNAPSHOT OUTPUT_DIR
+  stream SNAPSHOT OUTPUT_DIR
     Streams the SNAPSHOT into OUTPUT_DIR as a full (milestone) bin.
   
-  stream diff SNAPSHOT_FROM SNAPSHOT_TO OUTPUT_DIR
-    Streams the difference between SNAPSHOTs into OUTPUT_DIR as a diff bin.
-  
   list
     List snapshots and their rank.
   
@@ -607,12 +464,6 @@ Verbs:
   
   gc
     Drops old local snapshots based on garbage collector settings.
-  
-  gc greedy
-    Drop ALL snapshots except the newest Rank 2.
-  
-  gc COUNT
-    Drop COUNT oldest snapshots.
 """.format(cmd=sys.argv[0]))
 
 if __name__ == "__main__":
@@ -629,8 +480,7 @@ if __name__ == "__main__":
 	
 	try:
 		verb_router[verb](sys.argv[2:])
-	except UsageError as e:
-		print("!!! %s" %(e))
+	except UsageError:
 		print()
 		print_help()
 		sys.exit(1)
diff --git a/cfg/config.ini b/cfg/config.ini
index f3dc5a9..f5b72b0 100644
--- a/cfg/config.ini
+++ b/cfg/config.ini
@@ -30,15 +30,9 @@ dir = /mnt/pool/subvol/_backup
 
 [gc]
 # How many snapshots of each Rank to keep around.
+# Note: pruning is only performed when a new Rank 2 snapshot is attempted.
 # Default values are 25, 36, and 42, i.e. 5 hours for Rank 0, 2 days for Rank 1,
 # and a week for Rank 2.
 rank_0_count=25
 rank_1_count=36
 rank_2_count=42
-
-[monitoring]
-# GETs this URL before starting a rank2 snapdhot
-rank2_start_url = 
-
-# GETs this URL after successfully completing a rank2 snapshot
-rank2_end_url = 
diff --git a/systemd/btv-backup.service b/systemd/btv-backup.service
index d63bec8..19eb0cb 100644
--- a/systemd/btv-backup.service
+++ b/systemd/btv-backup.service
@@ -1,6 +1,5 @@
 [Unit]
 Description=Filesystem snapshot (with offsite backup)
-ConditionPathExists=!/run/lock/btv/serialization.lock
 
 [Service]
 Type=oneshot
diff --git a/unpack.sh b/unpack.sh
deleted file mode 100644
index f78a8ba..0000000
--- a/unpack.sh
+++ /dev/null
@@ -1,24 +0,0 @@
-#! /bin/zsh
-
-TIMESTAMP=($(basename "$(pwd)"))
-OUTDIR="$1"
-KEYFILE="$2"
-
-function die {
-	>&2 echo "$2"
-	exit $1
-}
-
-[[ "$0" != "./unpack.sh" ]] && die 1 "This can only be executed from the snapshot directory itself."
-[[ ! -d "$OUTDIR" ]]       && die 1 "The first argument must be a directory to unpack subvolumes into."
-[[ ! -f "$KEYFILE" ]]      && die 1 "The second argument must be a readable keyfile."
-./check-integrity.sh       || die 2 "This snapshot failed integrity checks."
-
-### end of checks
-
-for ARCHIVE in *btrfs.zst.aes
-do
-	openssl enc -d -aes-256-cbc -pbkdf2 -salt -pass "file:$KEYFILE" < "$ARCHIVE" | zstd -d | btrfs receive "$OUTDIR" || die 3 "Failed to unpack subvolume."
-	SUBVOL_NAME=${ARCHIVE%%.btrfs.zst.aes}
-	mv "${OUTDIR}/${SUBVOL_NAME}" "${OUTDIR}/${SUBVOL_NAME}.${TIMESTAMP[1]}" || die 4 "Failed to rename subvolume."
-done