diff --git a/archiver_test.go b/archiver_test.go
index 9aa9bffb4..c639be6ab 100644
--- a/archiver_test.go
+++ b/archiver_test.go
@@ -3,7 +3,6 @@ package restic_test
 import (
 	"bytes"
 	"crypto/sha256"
-	"flag"
 	"io"
 	"testing"
 
@@ -15,7 +14,6 @@ import (
 	. "github.com/restic/restic/test"
 )
 
-var benchArchiveDirectory = flag.String("test.benchdir", ".", "benchmark archiving a real directory (default: .)")
 var testPol = chunker.Pol(0x3DA3358B4DC173)
 
 type Rdr interface {
@@ -48,12 +46,12 @@ func benchmarkChunkEncrypt(b testing.TB, buf, buf2 []byte, rd Rdr, key *crypto.K
 }
 
 func BenchmarkChunkEncrypt(b *testing.B) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
 	data := Random(23, 10<<20) // 10MiB
 	rd := bytes.NewReader(data)
 
-	s := SetupRepo(b)
-	defer TeardownRepo(b, s)
-
 	buf := make([]byte, chunker.MaxSize)
 	buf2 := make([]byte, chunker.MaxSize)
 
@@ -61,7 +59,7 @@ func BenchmarkChunkEncrypt(b *testing.B) {
 	b.SetBytes(int64(len(data)))
 
 	for i := 0; i < b.N; i++ {
-		benchmarkChunkEncrypt(b, buf, buf2, rd, s.Key())
+		benchmarkChunkEncrypt(b, buf, buf2, rd, repo.Key())
 	}
 }
 
@@ -82,8 +80,8 @@ func benchmarkChunkEncryptP(b *testing.PB, buf []byte, rd Rdr, key *crypto.Key)
 }
 
 func BenchmarkChunkEncryptParallel(b *testing.B) {
-	s := SetupRepo(b)
-	defer TeardownRepo(b, s)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	data := Random(23, 10<<20) // 10MiB
 
@@ -95,25 +93,25 @@ func BenchmarkChunkEncryptParallel(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
 			rd := bytes.NewReader(data)
-			benchmarkChunkEncryptP(pb, buf, rd, s.Key())
+			benchmarkChunkEncryptP(pb, buf, rd, repo.Key())
 		}
 	})
 }
 
 func archiveDirectory(b testing.TB) {
-	repo := SetupRepo(b)
-	defer TeardownRepo(b, repo)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	arch := restic.NewArchiver(repo)
 
-	_, id, err := arch.Snapshot(nil, []string{*benchArchiveDirectory}, nil)
+	_, id, err := arch.Snapshot(nil, []string{BenchArchiveDirectory}, nil)
 	OK(b, err)
 
 	b.Logf("snapshot archived as %v", id)
 }
 
 func TestArchiveDirectory(t *testing.T) {
-	if *benchArchiveDirectory == "" {
+	if BenchArchiveDirectory == "" {
 		t.Skip("benchdir not set, skipping TestArchiveDirectory")
 	}
 
@@ -121,7 +119,7 @@ func TestArchiveDirectory(t *testing.T) {
 }
 
 func BenchmarkArchiveDirectory(b *testing.B) {
-	if *benchArchiveDirectory == "" {
+	if BenchArchiveDirectory == "" {
 		b.Skip("benchdir not set, skipping BenchmarkArchiveDirectory")
 	}
 
@@ -131,13 +129,13 @@ func BenchmarkArchiveDirectory(b *testing.B) {
 }
 
 func archiveWithDedup(t testing.TB) {
-	if *benchArchiveDirectory == "" {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	if BenchArchiveDirectory == "" {
 		t.Skip("benchdir not set, skipping TestArchiverDedup")
 	}
 
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
-
 	var cnt struct {
 		before, after, after2 struct {
 			packs, dataBlobs, treeBlobs uint
@@ -145,7 +143,7 @@ func archiveWithDedup(t testing.TB) {
 	}
 
 	// archive a few files
-	sn := SnapshotDir(t, repo, *benchArchiveDirectory, nil)
+	sn := SnapshotDir(t, repo, BenchArchiveDirectory, nil)
 	t.Logf("archived snapshot %v", sn.ID().Str())
 
 	// get archive stats
@@ -156,7 +154,7 @@ func archiveWithDedup(t testing.TB) {
 		cnt.before.packs, cnt.before.dataBlobs, cnt.before.treeBlobs)
 
 	// archive the same files again, without parent snapshot
-	sn2 := SnapshotDir(t, repo, *benchArchiveDirectory, nil)
+	sn2 := SnapshotDir(t, repo, BenchArchiveDirectory, nil)
 	t.Logf("archived snapshot %v", sn2.ID().Str())
 
 	// get archive stats again
@@ -173,7 +171,7 @@ func archiveWithDedup(t testing.TB) {
 	}
 
 	// archive the same files again, with a parent snapshot
-	sn3 := SnapshotDir(t, repo, *benchArchiveDirectory, sn2.ID())
+	sn3 := SnapshotDir(t, repo, BenchArchiveDirectory, sn2.ID())
 	t.Logf("archived snapshot %v, parent %v", sn3.ID().Str(), sn2.ID().Str())
 
 	// get archive stats again
@@ -195,23 +193,23 @@ func TestArchiveDedup(t *testing.T) {
 }
 
 func BenchmarkLoadTree(t *testing.B) {
-	if *benchArchiveDirectory == "" {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	if BenchArchiveDirectory == "" {
 		t.Skip("benchdir not set, skipping TestArchiverDedup")
 	}
 
-	s := SetupRepo(t)
-	defer TeardownRepo(t, s)
-
 	// archive a few files
-	arch := restic.NewArchiver(s)
-	sn, _, err := arch.Snapshot(nil, []string{*benchArchiveDirectory}, nil)
+	arch := restic.NewArchiver(repo)
+	sn, _, err := arch.Snapshot(nil, []string{BenchArchiveDirectory}, nil)
 	OK(t, err)
 	t.Logf("archived snapshot %v", sn.ID())
 
 	list := make([]backend.ID, 0, 10)
 	done := make(chan struct{})
 
-	for blob := range s.Index().Each(done) {
+	for blob := range repo.Index().Each(done) {
 		if blob.Type != pack.Tree {
 			continue
 		}
@@ -228,7 +226,7 @@ func BenchmarkLoadTree(t *testing.B) {
 
 	for i := 0; i < t.N; i++ {
 		for _, id := range list {
-			_, err := restic.LoadTree(s, id)
+			_, err := restic.LoadTree(repo, id)
 			OK(t, err)
 		}
 	}
diff --git a/cache_test.go b/cache_test.go
index 6f342dc39..b480b5869 100644
--- a/cache_test.go
+++ b/cache_test.go
@@ -8,8 +8,8 @@ import (
 )
 
 func TestCache(t *testing.T) {
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	_, err := restic.NewCache(repo, "")
 	OK(t, err)
@@ -17,7 +17,7 @@ func TestCache(t *testing.T) {
 	arch := restic.NewArchiver(repo)
 
 	// archive some files, this should automatically cache all blobs from the snapshot
-	_, _, err = arch.Snapshot(nil, []string{*benchArchiveDirectory}, nil)
+	_, _, err = arch.Snapshot(nil, []string{BenchArchiveDirectory}, nil)
 
 	// TODO: test caching index
 }
diff --git a/chunker/chunker_test.go b/chunker/chunker_test.go
index 5c38d2b0d..6a7f30a7d 100644
--- a/chunker/chunker_test.go
+++ b/chunker/chunker_test.go
@@ -5,12 +5,10 @@ import (
 	"crypto/md5"
 	"crypto/sha256"
 	"encoding/hex"
-	"flag"
 	"hash"
 	"io"
 	"io/ioutil"
 	"math/rand"
-	"os"
 	"testing"
 	"time"
 
@@ -18,8 +16,6 @@ import (
 	. "github.com/restic/restic/test"
 )
 
-var benchmarkFile = flag.String("bench.file", "", "read from this file for benchmark")
-
 func parseDigest(s string) []byte {
 	d, err := hex.DecodeString(s)
 	if err != nil {
@@ -247,29 +243,8 @@ func TestChunkerWithoutHash(t *testing.T) {
 }
 
 func benchmarkChunker(b *testing.B, hash hash.Hash) {
-	var (
-		rd   io.ReadSeeker
-		size int
-	)
-
-	if *benchmarkFile != "" {
-		b.Logf("using file %q for benchmark", *benchmarkFile)
-		f, err := os.Open(*benchmarkFile)
-		if err != nil {
-			b.Fatalf("open(%q): %v", *benchmarkFile, err)
-		}
-
-		fi, err := f.Stat()
-		if err != nil {
-			b.Fatalf("lstat(%q): %v", *benchmarkFile, err)
-		}
-
-		size = int(fi.Size())
-		rd = f
-	} else {
-		size = 10 * 1024 * 1024
-		rd = bytes.NewReader(getRandom(23, size))
-	}
+	size := 10 * 1024 * 1024
+	rd := bytes.NewReader(getRandom(23, size))
 
 	b.ResetTimer()
 	b.SetBytes(int64(size))
diff --git a/cmd/restic/cmd_backup.go b/cmd/restic/cmd_backup.go
index 2ab9dc5e0..32d486329 100644
--- a/cmd/restic/cmd_backup.go
+++ b/cmd/restic/cmd_backup.go
@@ -215,12 +215,18 @@ func (cmd CmdBackup) Execute(args []string) error {
 		target = append(target, d)
 	}
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
 	if err != nil {
 		return err
 	}
 
-	err = s.LoadIndex()
+	lock, err := lockRepo(repo)
+	defer unlockRepo(lock)
+	if err != nil {
+		return err
+	}
+
+	err = repo.LoadIndex()
 	if err != nil {
 		return err
 	}
@@ -229,7 +235,7 @@ func (cmd CmdBackup) Execute(args []string) error {
 
 	// Force using a parent
 	if !cmd.Force && cmd.Parent != "" {
-		parentSnapshotID, err = restic.FindSnapshot(s, cmd.Parent)
+		parentSnapshotID, err = restic.FindSnapshot(repo, cmd.Parent)
 		if err != nil {
 			return fmt.Errorf("invalid id %q: %v", cmd.Parent, err)
 		}
@@ -239,7 +245,7 @@ func (cmd CmdBackup) Execute(args []string) error {
 
 	// Find last snapshot to set it as parent, if not already set
 	if !cmd.Force && parentSnapshotID == nil {
-		parentSnapshotID, err = findLatestSnapshot(s, target)
+		parentSnapshotID, err = findLatestSnapshot(repo, target)
 		if err != nil {
 			return err
 		}
@@ -258,7 +264,7 @@ func (cmd CmdBackup) Execute(args []string) error {
 	// 	return true
 	// }
 
-	arch := restic.NewArchiver(s)
+	arch := restic.NewArchiver(repo)
 
 	arch.Error = func(dir string, fi os.FileInfo, err error) error {
 		// TODO: make ignoring errors configurable
diff --git a/cmd/restic/cmd_cache.go b/cmd/restic/cmd_cache.go
index 26a6b7970..39733b997 100644
--- a/cmd/restic/cmd_cache.go
+++ b/cmd/restic/cmd_cache.go
@@ -29,18 +29,24 @@ func (cmd CmdCache) Execute(args []string) error {
 	// 	return fmt.Errorf("wrong number of parameters, Usage: %s", cmd.Usage())
 	// }
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
 	if err != nil {
 		return err
 	}
 
-	cache, err := restic.NewCache(s, cmd.global.CacheDir)
+	lock, err := lockRepo(repo)
+	defer unlockRepo(lock)
+	if err != nil {
+		return err
+	}
+
+	cache, err := restic.NewCache(repo, cmd.global.CacheDir)
 	if err != nil {
 		return err
 	}
 
 	fmt.Printf("clear cache for old snapshots\n")
-	err = cache.Clear(s)
+	err = cache.Clear(repo)
 	if err != nil {
 		return err
 	}
diff --git a/cmd/restic/cmd_cat.go b/cmd/restic/cmd_cat.go
index 65345cfe7..6f22670ea 100644
--- a/cmd/restic/cmd_cat.go
+++ b/cmd/restic/cmd_cat.go
@@ -37,7 +37,13 @@ func (cmd CmdCat) Execute(args []string) error {
 		return fmt.Errorf("type or ID not specified, Usage: %s", cmd.Usage())
 	}
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
+	if err != nil {
+		return err
+	}
+
+	lock, err := lockRepo(repo)
+	defer unlockRepo(lock)
 	if err != nil {
 		return err
 	}
@@ -55,7 +61,7 @@ func (cmd CmdCat) Execute(args []string) error {
 			}
 
 			// find snapshot id with prefix
-			id, err = restic.FindSnapshot(s, args[1])
+			id, err = restic.FindSnapshot(repo, args[1])
 			if err != nil {
 				return err
 			}
@@ -65,7 +71,7 @@ func (cmd CmdCat) Execute(args []string) error {
 	// handle all types that don't need an index
 	switch tpe {
 	case "config":
-		buf, err := json.MarshalIndent(s.Config, "", "  ")
+		buf, err := json.MarshalIndent(repo.Config, "", "  ")
 		if err != nil {
 			return err
 		}
@@ -73,7 +79,7 @@ func (cmd CmdCat) Execute(args []string) error {
 		fmt.Println(string(buf))
 		return nil
 	case "index":
-		buf, err := s.Load(backend.Index, id)
+		buf, err := repo.Load(backend.Index, id)
 		if err != nil {
 			return err
 		}
@@ -83,7 +89,7 @@ func (cmd CmdCat) Execute(args []string) error {
 
 	case "snapshot":
 		sn := &restic.Snapshot{}
-		err = s.LoadJSONUnpacked(backend.Snapshot, id, sn)
+		err = repo.LoadJSONUnpacked(backend.Snapshot, id, sn)
 		if err != nil {
 			return err
 		}
@@ -97,7 +103,7 @@ func (cmd CmdCat) Execute(args []string) error {
 
 		return nil
 	case "key":
-		rd, err := s.Backend().Get(backend.Key, id.String())
+		rd, err := repo.Backend().Get(backend.Key, id.String())
 		if err != nil {
 			return err
 		}
@@ -118,7 +124,7 @@ func (cmd CmdCat) Execute(args []string) error {
 		fmt.Println(string(buf))
 		return nil
 	case "masterkey":
-		buf, err := json.MarshalIndent(s.Key(), "", "  ")
+		buf, err := json.MarshalIndent(repo.Key(), "", "  ")
 		if err != nil {
 			return err
 		}
@@ -126,18 +132,30 @@ func (cmd CmdCat) Execute(args []string) error {
 		fmt.Println(string(buf))
 		return nil
 	case "lock":
-		return errors.New("not yet implemented")
+		lock, err := restic.LoadLock(repo, id)
+		if err != nil {
+			return err
+		}
+
+		buf, err := json.MarshalIndent(&lock, "", "  ")
+		if err != nil {
+			return err
+		}
+
+		fmt.Println(string(buf))
+
+		return nil
 	}
 
 	// load index, handle all the other types
-	err = s.LoadIndex()
+	err = repo.LoadIndex()
 	if err != nil {
 		return err
 	}
 
 	switch tpe {
 	case "pack":
-		rd, err := s.Backend().Get(backend.Data, id.String())
+		rd, err := repo.Backend().Get(backend.Data, id.String())
 		if err != nil {
 			return err
 		}
@@ -146,7 +164,7 @@ func (cmd CmdCat) Execute(args []string) error {
 		return err
 
 	case "blob":
-		data, err := s.LoadBlob(pack.Data, id)
+		data, err := repo.LoadBlob(pack.Data, id)
 		if err == nil {
 			_, err = os.Stdout.Write(data)
 			return err
@@ -158,7 +176,7 @@ func (cmd CmdCat) Execute(args []string) error {
 	case "tree":
 		debug.Log("cat", "cat tree %v", id.Str())
 		tree := restic.NewTree()
-		err = s.LoadJSONPack(pack.Tree, id, tree)
+		err = repo.LoadJSONPack(pack.Tree, id, tree)
 		if err != nil {
 			debug.Log("cat", "unable to load tree %v: %v", id.Str(), err)
 			return err
diff --git a/cmd/restic/cmd_dump.go b/cmd/restic/cmd_dump.go
index b80e61509..9a12ea308 100644
--- a/cmd/restic/cmd_dump.go
+++ b/cmd/restic/cmd_dump.go
@@ -109,6 +109,12 @@ func (cmd CmdDump) Execute(args []string) error {
 		return err
 	}
 
+	lock, err := lockRepo(repo)
+	defer unlockRepo(lock)
+	if err != nil {
+		return err
+	}
+
 	err = repo.LoadIndex()
 	if err != nil {
 		return err
diff --git a/cmd/restic/cmd_find.go b/cmd/restic/cmd_find.go
index c1a56ebc6..33b91fe43 100644
--- a/cmd/restic/cmd_find.go
+++ b/cmd/restic/cmd_find.go
@@ -157,7 +157,13 @@ func (c CmdFind) Execute(args []string) error {
 		}
 	}
 
-	s, err := c.global.OpenRepository()
+	repo, err := c.global.OpenRepository()
+	if err != nil {
+		return err
+	}
+
+	lock, err := lockRepo(repo)
+	defer unlockRepo(lock)
 	if err != nil {
 		return err
 	}
@@ -165,18 +171,18 @@ func (c CmdFind) Execute(args []string) error {
 	c.pattern = args[0]
 
 	if c.Snapshot != "" {
-		snapshotID, err := restic.FindSnapshot(s, c.Snapshot)
+		snapshotID, err := restic.FindSnapshot(repo, c.Snapshot)
 		if err != nil {
 			return fmt.Errorf("invalid id %q: %v", args[1], err)
 		}
 
-		return c.findInSnapshot(s, snapshotID)
+		return c.findInSnapshot(repo, snapshotID)
 	}
 
 	done := make(chan struct{})
 	defer close(done)
-	for snapshotID := range s.List(backend.Snapshot, done) {
-		err := c.findInSnapshot(s, snapshotID)
+	for snapshotID := range repo.List(backend.Snapshot, done) {
+		err := c.findInSnapshot(repo, snapshotID)
 
 		if err != nil {
 			return err
diff --git a/cmd/restic/cmd_fsck.go b/cmd/restic/cmd_fsck.go
index 17a0608ce..b4e8d3e0d 100644
--- a/cmd/restic/cmd_fsck.go
+++ b/cmd/restic/cmd_fsck.go
@@ -190,23 +190,29 @@ func (cmd CmdFsck) Execute(args []string) error {
 		cmd.Orphaned = true
 	}
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
 	if err != nil {
 		return err
 	}
 
-	err = s.LoadIndex()
+	lock, err := lockRepoExclusive(repo)
+	defer unlockRepo(lock)
+	if err != nil {
+		return err
+	}
+
+	err = repo.LoadIndex()
 	if err != nil {
 		return err
 	}
 
 	if cmd.Snapshot != "" {
-		id, err := restic.FindSnapshot(s, cmd.Snapshot)
+		id, err := restic.FindSnapshot(repo, cmd.Snapshot)
 		if err != nil {
 			return fmt.Errorf("invalid id %q: %v", cmd.Snapshot, err)
 		}
 
-		err = fsckSnapshot(cmd, s, id)
+		err = fsckSnapshot(cmd, repo, id)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "check for snapshot %v failed\n", id)
 		}
@@ -223,8 +229,8 @@ func (cmd CmdFsck) Execute(args []string) error {
 	defer close(done)
 
 	var firstErr error
-	for id := range s.List(backend.Snapshot, done) {
-		err = fsckSnapshot(cmd, s, id)
+	for id := range repo.List(backend.Snapshot, done) {
+		err = fsckSnapshot(cmd, repo, id)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "check for snapshot %v failed\n", id)
 			firstErr = err
@@ -241,7 +247,7 @@ func (cmd CmdFsck) Execute(args []string) error {
 	cnt[pack.Data] = cmd.o_data
 	cnt[pack.Tree] = cmd.o_trees
 
-	for blob := range s.Index().Each(done) {
+	for blob := range repo.Index().Each(done) {
 		debug.Log("restic.fsck", "checking %v blob %v\n", blob.Type, blob.ID)
 
 		err = cnt[blob.Type].Find(blob.ID)
diff --git a/cmd/restic/cmd_key.go b/cmd/restic/cmd_key.go
index ad1a358fd..c585ae4cd 100644
--- a/cmd/restic/cmd_key.go
+++ b/cmd/restic/cmd_key.go
@@ -116,25 +116,49 @@ func (cmd CmdKey) Execute(args []string) error {
 		return fmt.Errorf("wrong number of arguments, Usage: %s", cmd.Usage())
 	}
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
 	if err != nil {
 		return err
 	}
 
 	switch args[0] {
 	case "list":
-		return cmd.listKeys(s)
-	case "add":
-		return cmd.addKey(s)
-	case "rm":
-		id, err := backend.Find(s.Backend(), backend.Key, args[1])
+		lock, err := lockRepo(repo)
+		defer unlockRepo(lock)
 		if err != nil {
 			return err
 		}
 
-		return cmd.deleteKey(s, id)
+		return cmd.listKeys(repo)
+	case "add":
+		lock, err := lockRepo(repo)
+		defer unlockRepo(lock)
+		if err != nil {
+			return err
+		}
+
+		return cmd.addKey(repo)
+	case "rm":
+		lock, err := lockRepoExclusive(repo)
+		defer unlockRepo(lock)
+		if err != nil {
+			return err
+		}
+
+		id, err := backend.Find(repo.Backend(), backend.Key, args[1])
+		if err != nil {
+			return err
+		}
+
+		return cmd.deleteKey(repo, id)
 	case "passwd":
-		return cmd.changePassword(s)
+		lock, err := lockRepoExclusive(repo)
+		defer unlockRepo(lock)
+		if err != nil {
+			return err
+		}
+
+		return cmd.changePassword(repo)
 	}
 
 	return nil
diff --git a/cmd/restic/cmd_list.go b/cmd/restic/cmd_list.go
index bd01e6eda..c8ea6c65c 100644
--- a/cmd/restic/cmd_list.go
+++ b/cmd/restic/cmd_list.go
@@ -30,7 +30,13 @@ func (cmd CmdList) Execute(args []string) error {
 		return fmt.Errorf("type not specified, Usage: %s", cmd.Usage())
 	}
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
+	if err != nil {
+		return err
+	}
+
+	lock, err := lockRepo(repo)
+	defer unlockRepo(lock)
 	if err != nil {
 		return err
 	}
@@ -38,12 +44,12 @@ func (cmd CmdList) Execute(args []string) error {
 	var t backend.Type
 	switch args[0] {
 	case "blobs":
-		err = s.LoadIndex()
+		err = repo.LoadIndex()
 		if err != nil {
 			return err
 		}
 
-		for blob := range s.Index().Each(nil) {
+		for blob := range repo.Index().Each(nil) {
 			cmd.global.Printf("%s\n", blob.ID)
 		}
 
@@ -62,7 +68,7 @@ func (cmd CmdList) Execute(args []string) error {
 		return errors.New("invalid type")
 	}
 
-	for id := range s.List(t, nil) {
+	for id := range repo.List(t, nil) {
 		cmd.global.Printf("%s\n", id)
 	}
 
diff --git a/cmd/restic/cmd_ls.go b/cmd/restic/cmd_ls.go
index 59144befc..8ec904bbd 100644
--- a/cmd/restic/cmd_ls.go
+++ b/cmd/restic/cmd_ls.go
@@ -69,27 +69,27 @@ func (cmd CmdLs) Execute(args []string) error {
 		return fmt.Errorf("wrong number of arguments, Usage: %s", cmd.Usage())
 	}
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
 	if err != nil {
 		return err
 	}
 
-	err = s.LoadIndex()
+	err = repo.LoadIndex()
 	if err != nil {
 		return err
 	}
 
-	id, err := restic.FindSnapshot(s, args[0])
+	id, err := restic.FindSnapshot(repo, args[0])
 	if err != nil {
 		return err
 	}
 
-	sn, err := restic.LoadSnapshot(s, id)
+	sn, err := restic.LoadSnapshot(repo, id)
 	if err != nil {
 		return err
 	}
 
 	fmt.Printf("snapshot of %v at %s:\n", sn.Paths, sn.Time)
 
-	return printTree("", s, sn.Tree)
+	return printTree("", repo, sn.Tree)
 }
diff --git a/cmd/restic/cmd_restore.go b/cmd/restic/cmd_restore.go
index 1f3697d4d..393d0347d 100644
--- a/cmd/restic/cmd_restore.go
+++ b/cmd/restic/cmd_restore.go
@@ -30,17 +30,23 @@ func (cmd CmdRestore) Execute(args []string) error {
 		return fmt.Errorf("wrong number of arguments, Usage: %s", cmd.Usage())
 	}
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
 	if err != nil {
 		return err
 	}
 
-	err = s.LoadIndex()
+	lock, err := lockRepo(repo)
+	defer unlockRepo(lock)
 	if err != nil {
 		return err
 	}
 
-	id, err := restic.FindSnapshot(s, args[0])
+	err = repo.LoadIndex()
+	if err != nil {
+		return err
+	}
+
+	id, err := restic.FindSnapshot(repo, args[0])
 	if err != nil {
 		cmd.global.Exitf(1, "invalid id %q: %v", args[0], err)
 	}
@@ -48,7 +54,7 @@ func (cmd CmdRestore) Execute(args []string) error {
 	target := args[1]
 
 	// create restorer
-	res, err := restic.NewRestorer(s, id)
+	res, err := restic.NewRestorer(repo, id)
 	if err != nil {
 		cmd.global.Exitf(2, "creating restorer failed: %v\n", err)
 	}
diff --git a/cmd/restic/cmd_snapshots.go b/cmd/restic/cmd_snapshots.go
index f1f8ba31e..38e2046ad 100644
--- a/cmd/restic/cmd_snapshots.go
+++ b/cmd/restic/cmd_snapshots.go
@@ -94,7 +94,13 @@ func (cmd CmdSnapshots) Execute(args []string) error {
 		return fmt.Errorf("wrong number of arguments, usage: %s", cmd.Usage())
 	}
 
-	s, err := cmd.global.OpenRepository()
+	repo, err := cmd.global.OpenRepository()
+	if err != nil {
+		return err
+	}
+
+	lock, err := lockRepo(repo)
+	defer unlockRepo(lock)
 	if err != nil {
 		return err
 	}
@@ -107,8 +113,8 @@ func (cmd CmdSnapshots) Execute(args []string) error {
 	defer close(done)
 
 	list := []*restic.Snapshot{}
-	for id := range s.List(backend.Snapshot, done) {
-		sn, err := restic.LoadSnapshot(s, id)
+	for id := range repo.List(backend.Snapshot, done) {
+		sn, err := restic.LoadSnapshot(repo, id)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "error loading snapshot %s: %v\n", id, err)
 			continue
@@ -127,7 +133,7 @@ func (cmd CmdSnapshots) Execute(args []string) error {
 		}
 	}
 
-	plen, err := s.PrefixLength(backend.Snapshot)
+	plen, err := repo.PrefixLength(backend.Snapshot)
 	if err != nil {
 		return err
 	}
diff --git a/cmd/restic/cmd_unlock.go b/cmd/restic/cmd_unlock.go
new file mode 100644
index 000000000..47345350c
--- /dev/null
+++ b/cmd/restic/cmd_unlock.go
@@ -0,0 +1,43 @@
+package main
+
+import "github.com/restic/restic"
+
+type CmdUnlock struct {
+	RemoveAll bool `long:"remove-all" description:"Remove all locks, even stale ones"`
+
+	global *GlobalOptions
+}
+
+func init() {
+	_, err := parser.AddCommand("unlock",
+		"remove locks",
+		"The unlock command checks for stale locks and removes them",
+		&CmdUnlock{global: &globalOpts})
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (cmd CmdUnlock) Usage() string {
+	return "[unlock-options]"
+}
+
+func (cmd CmdUnlock) Execute(args []string) error {
+	repo, err := cmd.global.OpenRepository()
+	if err != nil {
+		return err
+	}
+
+	fn := restic.RemoveStaleLocks
+	if cmd.RemoveAll {
+		fn = restic.RemoveAllLocks
+	}
+
+	err = fn(repo)
+	if err != nil {
+		return err
+	}
+
+	cmd.global.Verbosef("successfully removed locks\n")
+	return nil
+}
diff --git a/cmd/restic/lock.go b/cmd/restic/lock.go
new file mode 100644
index 000000000..5f6c18802
--- /dev/null
+++ b/cmd/restic/lock.go
@@ -0,0 +1,93 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/restic/restic"
+	"github.com/restic/restic/debug"
+	"github.com/restic/restic/repository"
+)
+
+var globalLocks []*restic.Lock
+
+func lockRepo(repo *repository.Repository) (*restic.Lock, error) {
+	return lockRepository(repo, false)
+}
+
+func lockRepoExclusive(repo *repository.Repository) (*restic.Lock, error) {
+	return lockRepository(repo, true)
+}
+
+func lockRepository(repo *repository.Repository, exclusive bool) (*restic.Lock, error) {
+	lockFn := restic.NewLock
+	if exclusive {
+		lockFn = restic.NewExclusiveLock
+	}
+
+	lock, err := lockFn(repo)
+	if err != nil {
+		if restic.IsAlreadyLocked(err) {
+			tpe := ""
+			if exclusive {
+				tpe = " exclusive"
+			}
+			fmt.Fprintf(os.Stderr, "unable to acquire%s lock for operation:\n", tpe)
+			fmt.Fprintln(os.Stderr, err)
+			fmt.Fprintf(os.Stderr, "\nthe `unlock` command can be used to remove stale locks\n")
+			os.Exit(1)
+		}
+
+		return nil, err
+	}
+
+	globalLocks = append(globalLocks, lock)
+
+	return lock, err
+}
+
+func unlockRepo(lock *restic.Lock) error {
+	if err := lock.Unlock(); err != nil {
+		return err
+	}
+
+	for i := 0; i < len(globalLocks); i++ {
+		if lock == globalLocks[i] {
+			globalLocks = append(globalLocks[:i], globalLocks[i+1:]...)
+			return nil
+		}
+	}
+
+	return nil
+}
+
+func unlockAll() error {
+	debug.Log("unlockAll", "unlocking %d locks", len(globalLocks))
+	for _, lock := range globalLocks {
+		if err := lock.Unlock(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func init() {
+	c := make(chan os.Signal)
+	signal.Notify(c, syscall.SIGINT)
+
+	go CleanupHandler(c)
+}
+
+// CleanupHandler handles the SIGINT signal.
+func CleanupHandler(c <-chan os.Signal) {
+	for s := range c {
+		debug.Log("CleanupHandler", "signal %v received, cleaning up", s)
+		fmt.Println("\x1b[2KInterrupt received, cleaning up")
+		unlockAll()
+		fmt.Println("exiting")
+		os.Exit(0)
+	}
+}
diff --git a/crypto/crypto_test.go b/crypto/crypto_test.go
index faba9970c..e8911c086 100644
--- a/crypto/crypto_test.go
+++ b/crypto/crypto_test.go
@@ -2,7 +2,6 @@ package crypto_test
 
 import (
 	"bytes"
-	"flag"
 	"io"
 	"io/ioutil"
 	"os"
@@ -13,13 +12,13 @@ import (
 	. "github.com/restic/restic/test"
 )
 
-var testLargeCrypto = flag.Bool("test.largecrypto", false, "also test crypto functions with large payloads")
+const testLargeCrypto = false
 
 func TestEncryptDecrypt(t *testing.T) {
 	k := crypto.NewRandomKey()
 
 	tests := []int{5, 23, 2<<18 + 23, 1 << 20}
-	if *testLargeCrypto {
+	if testLargeCrypto {
 		tests = append(tests, 7<<20+123)
 	}
 
@@ -117,7 +116,7 @@ func TestCornerCases(t *testing.T) {
 }
 
 func TestLargeEncrypt(t *testing.T) {
-	if !*testLargeCrypto {
+	if !testLargeCrypto {
 		t.SkipNow()
 	}
 
@@ -252,7 +251,7 @@ func TestEncryptStreamWriter(t *testing.T) {
 	k := crypto.NewRandomKey()
 
 	tests := []int{5, 23, 2<<18 + 23, 1 << 20}
-	if *testLargeCrypto {
+	if testLargeCrypto {
 		tests = append(tests, 7<<20+123)
 	}
 
@@ -286,7 +285,7 @@ func TestDecryptStreamReader(t *testing.T) {
 	k := crypto.NewRandomKey()
 
 	tests := []int{5, 23, 2<<18 + 23, 1 << 20}
-	if *testLargeCrypto {
+	if testLargeCrypto {
 		tests = append(tests, 7<<20+123)
 	}
 
@@ -320,7 +319,7 @@ func TestEncryptWriter(t *testing.T) {
 	k := crypto.NewRandomKey()
 
 	tests := []int{5, 23, 2<<18 + 23, 1 << 20}
-	if *testLargeCrypto {
+	if testLargeCrypto {
 		tests = append(tests, 7<<20+123)
 	}
 
diff --git a/doc/Design.md b/doc/Design.md
index 483ce3621..e1ce4f275 100644
--- a/doc/Design.md
+++ b/doc/Design.md
@@ -375,6 +375,47 @@ As can be seen from the output of the program `sha256sum`, the hash matches the
 plaintext hash from the map included in the tree above, so the correct data has
 been returned.
 
+Locks
+-----
+
+The restic repository structure is designed in a way that allows parallel
+access of multiple instance of restic and even parallel writes. However, there
+are some functions that work more efficient or even require exclusive access of
+the repository. In order to implement these functions, restic processes are
+required to create a lock on the repository before doing anything.
+
+Locks come in two types: Exclusive and non-exclusive locks. At most one
+process can have an exclusive lock on the repository, and during that time
+there mustn't be any other locks (exclusive and non-exclusive). There may be
+multiple non-exclusive locks in parallel.
+
+A lock is a file in the subdir `locks` whose filename is the storage ID of
+the contents. It is encrypted and authenticated the same way as other files
+in the repository and contains the following JSON structure:
+
+    {
+      "time": "2015-06-27T12:18:51.759239612+02:00",
+      "exclusive": false,
+      "hostname": "kasimir",
+      "username": "fd0",
+      "pid": 13607,
+      "uid": 1000,
+      "gid": 100
+    }
+
+The field `exclusive` defines the type of lock. When a new lock is to be
+created, restic checks all locks in the repository. When a lock is found, it
+is tested if the lock is stale, which is the case for locks with timestamps
+older than 30 minutes. If the lock was created on the same machine, even for
+younger locks it is tested whether the process is still alive by sending a
+signal to it. If that fails, restic assumes that the process is dead and
+considers the lock to be stale.
+
+When a new lock is to be created and no other conflicting locks are
+detected, restic creates a new lock, waits, and checks if other locks
+appeared in the repository. Depending on the type of the other locks and the
+lock to be created, restic either continues or fails.
+
 Backups and Deduplication
 =========================
 
diff --git a/lock.go b/lock.go
new file mode 100644
index 000000000..65d102323
--- /dev/null
+++ b/lock.go
@@ -0,0 +1,282 @@
+package restic
+
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"os/user"
+	"strconv"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/restic/restic/backend"
+	"github.com/restic/restic/debug"
+	"github.com/restic/restic/repository"
+)
+
+// Lock represents a process locking the repository for an operation.
+//
+// There are two types of locks: exclusive and non-exclusive. There may be many
+// different non-exclusive locks, but at most one exclusive lock, which can
+// only be acquired while no non-exclusive lock is held.
+type Lock struct {
+	Time      time.Time `json:"time"`
+	Exclusive bool      `json:"exclusive"`
+	Hostname  string    `json:"hostname"`
+	Username  string    `json:"username"`
+	PID       int       `json:"pid"`
+	UID       uint32    `json:"uid,omitempty"`
+	GID       uint32    `json:"gid,omitempty"`
+
+	repo   *repository.Repository
+	lockID backend.ID
+}
+
+// ErrAlreadyLocked is returned when NewLock or NewExclusiveLock are unable to
+// acquire the desired lock.
+type ErrAlreadyLocked struct {
+	otherLock *Lock
+}
+
+func (e ErrAlreadyLocked) Error() string {
+	return fmt.Sprintf("repository is already locked by %v", e.otherLock)
+}
+
+// IsAlreadyLocked returns true iff err is an instance of ErrAlreadyLocked.
+func IsAlreadyLocked(err error) bool {
+	if _, ok := err.(ErrAlreadyLocked); ok {
+		return true
+	}
+
+	return false
+}
+
+// NewLock returns a new, non-exclusive lock for the repository. If an
+// exclusive lock is already held by another process, ErrAlreadyLocked is
+// returned.
+func NewLock(repo *repository.Repository) (*Lock, error) {
+	return newLock(repo, false)
+}
+
+// NewExclusiveLock returns a new, exclusive lock for the repository. If
+// another lock (normal and exclusive) is already held by another process,
+// ErrAlreadyLocked is returned.
+func NewExclusiveLock(repo *repository.Repository) (*Lock, error) {
+	return newLock(repo, true)
+}
+
+const waitBeforeLockCheck = 200 * time.Millisecond
+
+func newLock(repo *repository.Repository, excl bool) (*Lock, error) {
+	lock := &Lock{
+		Time:      time.Now(),
+		PID:       os.Getpid(),
+		Exclusive: excl,
+		repo:      repo,
+	}
+
+	hn, err := os.Hostname()
+	if err == nil {
+		lock.Hostname = hn
+	}
+
+	if err = lock.fillUserInfo(); err != nil {
+		return nil, err
+	}
+
+	if err = lock.checkForOtherLocks(); err != nil {
+		return nil, err
+	}
+
+	err = lock.createLock()
+	if err != nil {
+		return nil, err
+	}
+
+	time.Sleep(waitBeforeLockCheck)
+
+	if err = lock.checkForOtherLocks(); err != nil {
+		lock.Unlock()
+		return nil, err
+	}
+
+	return lock, nil
+}
+
+func (l *Lock) fillUserInfo() error {
+	usr, err := user.Current()
+	if err != nil {
+		return nil
+	}
+	l.Username = usr.Username
+
+	uid, err := strconv.ParseInt(usr.Uid, 10, 32)
+	if err != nil {
+		return err
+	}
+	l.UID = uint32(uid)
+
+	gid, err := strconv.ParseInt(usr.Gid, 10, 32)
+	if err != nil {
+		return err
+	}
+	l.GID = uint32(gid)
+
+	return nil
+}
+
+// checkForOtherLocks looks for other locks that currently exist in the repository.
+//
+// If an exclusive lock is to be created, checkForOtherLocks returns an error
+// if there are any other locks, regardless if exclusive or not. If a
+// non-exclusive lock is to be created, an error is only returned when an
+// exclusive lock is found.
+func (l *Lock) checkForOtherLocks() error {
+	return eachLock(l.repo, func(id backend.ID, lock *Lock, err error) error {
+		if id.Equal(l.lockID) {
+			return nil
+		}
+
+		// ignore locks that cannot be loaded
+		if err != nil {
+			return nil
+		}
+
+		if l.Exclusive {
+			return ErrAlreadyLocked{otherLock: lock}
+		}
+
+		if !l.Exclusive && lock.Exclusive {
+			return ErrAlreadyLocked{otherLock: lock}
+		}
+
+		return nil
+	})
+}
+
+func eachLock(repo *repository.Repository, f func(backend.ID, *Lock, error) error) error {
+	done := make(chan struct{})
+	defer close(done)
+
+	for id := range repo.List(backend.Lock, done) {
+		lock, err := LoadLock(repo, id)
+		err = f(id, lock, err)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// createLock acquires the lock by creating a file in the repository.
+func (l *Lock) createLock() error {
+	id, err := l.repo.SaveJSONUnpacked(backend.Lock, l)
+	if err != nil {
+		return err
+	}
+
+	l.lockID = id
+	return nil
+}
+
+// Unlock removes the lock from the repository.
+func (l *Lock) Unlock() error {
+	if l == nil || l.lockID == nil {
+		return nil
+	}
+
+	return l.repo.Backend().Remove(backend.Lock, l.lockID.String())
+}
+
+var staleTimeout = 30 * time.Minute
+
+// Stale returns true if the lock is stale. A lock is stale if the timestamp is
+// older than 30 minutes or if it was created on the current machine and the
+// process isn't alive any more.
+func (l *Lock) Stale() bool {
+	debug.Log("Lock.Stale", "testing if lock %v for process %d is stale", l.lockID.Str(), l.PID)
+	if time.Now().Sub(l.Time) > staleTimeout {
+		debug.Log("Lock.Stale", "lock is stale, timestamp is too old: %v\n", l.Time)
+		return true
+	}
+
+	proc, err := os.FindProcess(l.PID)
+	defer proc.Release()
+	if err != nil {
+		debug.Log("Lock.Stale", "error searching for process %d: %v\n", l.PID, err)
+		return true
+	}
+
+	debug.Log("Lock.Stale", "sending SIGHUP to process %d\n", l.PID)
+	err = proc.Signal(syscall.SIGHUP)
+	if err != nil {
+		debug.Log("Lock.Stale", "signal error: %v, lock is probably stale\n", err)
+		return true
+	}
+
+	debug.Log("Lock.Stale", "lock not stale\n")
+	return false
+}
+
+func (l Lock) String() string {
+	text := fmt.Sprintf("PID %d on %s by %s (UID %d, GID %d)\nlock was created at %s (%s ago)\nstorage ID %v",
+		l.PID, l.Hostname, l.Username, l.UID, l.GID,
+		l.Time.Format("2006-01-02 15:04:05"), time.Since(l.Time),
+		l.lockID.Str())
+
+	if l.Stale() {
+		text += " (stale)"
+	}
+
+	return text
+}
+
+// listen for incoming SIGHUP and ignore
+var ignoreSIGHUP sync.Once
+
+func init() {
+	ignoreSIGHUP.Do(func() {
+		go func() {
+			c := make(chan os.Signal)
+			signal.Notify(c, syscall.SIGHUP)
+			for s := range c {
+				debug.Log("lock.ignoreSIGHUP", "Signal received: %v\n", s)
+			}
+		}()
+	})
+}
+
+// LoadLock loads and unserializes a lock from a repository.
+func LoadLock(repo *repository.Repository, id backend.ID) (*Lock, error) {
+	lock := &Lock{}
+	if err := repo.LoadJSONUnpacked(backend.Lock, id, lock); err != nil {
+		return nil, err
+	}
+	lock.lockID = id
+
+	return lock, nil
+}
+
+// RemoveStaleLocks deletes all locks detected as stale from the repository.
+func RemoveStaleLocks(repo *repository.Repository) error {
+	return eachLock(repo, func(id backend.ID, lock *Lock, err error) error {
+		// ignore locks that cannot be loaded
+		if err != nil {
+			return nil
+		}
+
+		if lock.Stale() {
+			return repo.Backend().Remove(backend.Lock, id.String())
+		}
+
+		return nil
+	})
+}
+
+func RemoveAllLocks(repo *repository.Repository) error {
+	return eachLock(repo, func(id backend.ID, lock *Lock, err error) error {
+		return repo.Backend().Remove(backend.Lock, id.String())
+	})
+}
diff --git a/lock_test.go b/lock_test.go
new file mode 100644
index 000000000..988c5d440
--- /dev/null
+++ b/lock_test.go
@@ -0,0 +1,197 @@
+package restic_test
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	"github.com/restic/restic"
+	"github.com/restic/restic/backend"
+	"github.com/restic/restic/repository"
+	. "github.com/restic/restic/test"
+)
+
+func TestLock(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	lock, err := restic.NewLock(repo)
+	OK(t, err)
+
+	OK(t, lock.Unlock())
+}
+
+func TestDoubleUnlock(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	lock, err := restic.NewLock(repo)
+	OK(t, err)
+
+	OK(t, lock.Unlock())
+
+	err = lock.Unlock()
+	Assert(t, err != nil,
+		"double unlock didn't return an error, got %v", err)
+}
+
+func TestMultipleLock(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	lock1, err := restic.NewLock(repo)
+	OK(t, err)
+
+	lock2, err := restic.NewLock(repo)
+	OK(t, err)
+
+	OK(t, lock1.Unlock())
+	OK(t, lock2.Unlock())
+}
+
+func TestLockExclusive(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	elock, err := restic.NewExclusiveLock(repo)
+	OK(t, err)
+	OK(t, elock.Unlock())
+}
+
+func TestLockOnExclusiveLockedRepo(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	elock, err := restic.NewExclusiveLock(repo)
+	OK(t, err)
+
+	lock, err := restic.NewLock(repo)
+	Assert(t, err != nil,
+		"create normal lock with exclusively locked repo didn't return an error")
+	Assert(t, restic.IsAlreadyLocked(err),
+		"create normal lock with exclusively locked repo didn't return the correct error")
+
+	OK(t, lock.Unlock())
+	OK(t, elock.Unlock())
+}
+
+func TestExclusiveLockOnLockedRepo(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	elock, err := restic.NewLock(repo)
+	OK(t, err)
+
+	lock, err := restic.NewExclusiveLock(repo)
+	Assert(t, err != nil,
+		"create normal lock with exclusively locked repo didn't return an error")
+	Assert(t, restic.IsAlreadyLocked(err),
+		"create normal lock with exclusively locked repo didn't return the correct error")
+
+	OK(t, lock.Unlock())
+	OK(t, elock.Unlock())
+}
+
+func createFakeLock(repo *repository.Repository, t time.Time, pid int) (backend.ID, error) {
+	newLock := &restic.Lock{Time: t, PID: pid}
+	return repo.SaveJSONUnpacked(backend.Lock, &newLock)
+}
+
+func removeLock(repo *repository.Repository, id backend.ID) error {
+	return repo.Backend().Remove(backend.Lock, id.String())
+}
+
+var staleLockTests = []struct {
+	timestamp time.Time
+	stale     bool
+	pid       int
+}{
+	{
+		timestamp: time.Now(),
+		stale:     false,
+		pid:       os.Getpid(),
+	},
+	{
+		timestamp: time.Now().Add(-time.Hour),
+		stale:     true,
+		pid:       os.Getpid(),
+	},
+	{
+		timestamp: time.Now().Add(3 * time.Minute),
+		stale:     false,
+		pid:       os.Getpid(),
+	},
+	{
+		timestamp: time.Now(),
+		stale:     true,
+		pid:       os.Getpid() + 500,
+	},
+}
+
+func TestLockStale(t *testing.T) {
+	for i, test := range staleLockTests {
+		lock := restic.Lock{
+			Time: test.timestamp,
+			PID:  test.pid,
+		}
+
+		Assert(t, lock.Stale() == test.stale,
+			"TestStaleLock: test %d failed: expected stale: %v, got %v",
+			i, test.stale, !test.stale)
+	}
+}
+
+func lockExists(repo *repository.Repository, t testing.TB, id backend.ID) bool {
+	exists, err := repo.Backend().Test(backend.Lock, id.String())
+	OK(t, err)
+
+	return exists
+}
+
+func TestLockWithStaleLock(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	id1, err := createFakeLock(repo, time.Now().Add(-time.Hour), os.Getpid())
+	OK(t, err)
+
+	id2, err := createFakeLock(repo, time.Now().Add(-time.Minute), os.Getpid())
+	OK(t, err)
+
+	id3, err := createFakeLock(repo, time.Now().Add(-time.Minute), os.Getpid()+500)
+	OK(t, err)
+
+	OK(t, restic.RemoveStaleLocks(repo))
+
+	Assert(t, lockExists(repo, t, id1) == false,
+		"stale lock still exists after RemoveStaleLocks was called")
+	Assert(t, lockExists(repo, t, id2) == true,
+		"non-stale lock was removed by RemoveStaleLocks")
+	Assert(t, lockExists(repo, t, id3) == false,
+		"stale lock still exists after RemoveStaleLocks was called")
+
+	OK(t, removeLock(repo, id2))
+}
+
+func TestRemoveAllLocks(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	id1, err := createFakeLock(repo, time.Now().Add(-time.Hour), os.Getpid())
+	OK(t, err)
+
+	id2, err := createFakeLock(repo, time.Now().Add(-time.Minute), os.Getpid())
+	OK(t, err)
+
+	id3, err := createFakeLock(repo, time.Now().Add(-time.Minute), os.Getpid()+500)
+	OK(t, err)
+
+	OK(t, restic.RemoveAllLocks(repo))
+
+	Assert(t, lockExists(repo, t, id1) == false,
+		"lock still exists after RemoveAllLocks was called")
+	Assert(t, lockExists(repo, t, id2) == false,
+		"lock still exists after RemoveAllLocks was called")
+	Assert(t, lockExists(repo, t, id3) == false,
+		"lock still exists after RemoveAllLocks was called")
+}
diff --git a/pipe/pipe_test.go b/pipe/pipe_test.go
index edb270e6f..42ff7c31d 100644
--- a/pipe/pipe_test.go
+++ b/pipe/pipe_test.go
@@ -1,7 +1,6 @@
 package pipe_test
 
 import (
-	"flag"
 	"os"
 	"path/filepath"
 	"sync"
@@ -12,9 +11,6 @@ import (
 	. "github.com/restic/restic/test"
 )
 
-var testWalkerPath = flag.String("test.walkerpath", ".", "pipeline walker testpath (default: .)")
-var maxWorkers = flag.Int("test.workers", 100, "max concurrency (default: 100)")
-
 func isFile(fi os.FileInfo) bool {
 	return fi.Mode()&(os.ModeType|os.ModeCharDevice) == 0
 }
@@ -27,7 +23,7 @@ func statPath(path string) (stats, error) {
 	var s stats
 
 	// count files and directories with filepath.Walk()
-	err := filepath.Walk(*testWalkerPath, func(p string, fi os.FileInfo, err error) error {
+	err := filepath.Walk(TestWalkerPath, func(p string, fi os.FileInfo, err error) error {
 		if fi == nil {
 			return err
 		}
@@ -44,15 +40,17 @@ func statPath(path string) (stats, error) {
 	return s, err
 }
 
+const maxWorkers = 100
+
 func TestPipelineWalkerWithSplit(t *testing.T) {
-	if *testWalkerPath == "" {
+	if TestWalkerPath == "" {
 		t.Skipf("walkerpath not set, skipping TestPipelineWalker")
 	}
 
-	before, err := statPath(*testWalkerPath)
+	before, err := statPath(TestWalkerPath)
 	OK(t, err)
 
-	t.Logf("walking path %s with %d dirs, %d files", *testWalkerPath,
+	t.Logf("walking path %s with %d dirs, %d files", TestWalkerPath,
 		before.dirs, before.files)
 
 	// account for top level dir
@@ -105,7 +103,7 @@ func TestPipelineWalkerWithSplit(t *testing.T) {
 	entCh := make(chan pipe.Entry)
 	dirCh := make(chan pipe.Dir)
 
-	for i := 0; i < *maxWorkers; i++ {
+	for i := 0; i < maxWorkers; i++ {
 		wg.Add(1)
 		go worker(&wg, done, entCh, dirCh)
 	}
@@ -120,7 +118,7 @@ func TestPipelineWalkerWithSplit(t *testing.T) {
 	}()
 
 	resCh := make(chan pipe.Result, 1)
-	err = pipe.Walk([]string{*testWalkerPath}, done, jobs, resCh)
+	err = pipe.Walk([]string{TestWalkerPath}, done, jobs, resCh)
 	OK(t, err)
 
 	// wait for all workers to terminate
@@ -129,21 +127,21 @@ func TestPipelineWalkerWithSplit(t *testing.T) {
 	// wait for top-level blob
 	<-resCh
 
-	t.Logf("walked path %s with %d dirs, %d files", *testWalkerPath,
+	t.Logf("walked path %s with %d dirs, %d files", TestWalkerPath,
 		after.dirs, after.files)
 
 	Assert(t, before == after, "stats do not match, expected %v, got %v", before, after)
 }
 
 func TestPipelineWalker(t *testing.T) {
-	if *testWalkerPath == "" {
+	if TestWalkerPath == "" {
 		t.Skipf("walkerpath not set, skipping TestPipelineWalker")
 	}
 
-	before, err := statPath(*testWalkerPath)
+	before, err := statPath(TestWalkerPath)
 	OK(t, err)
 
-	t.Logf("walking path %s with %d dirs, %d files", *testWalkerPath,
+	t.Logf("walking path %s with %d dirs, %d files", TestWalkerPath,
 		before.dirs, before.files)
 
 	// account for top level dir
@@ -194,13 +192,13 @@ func TestPipelineWalker(t *testing.T) {
 	done := make(chan struct{})
 	jobs := make(chan pipe.Job)
 
-	for i := 0; i < *maxWorkers; i++ {
+	for i := 0; i < maxWorkers; i++ {
 		wg.Add(1)
 		go worker(&wg, done, jobs)
 	}
 
 	resCh := make(chan pipe.Result, 1)
-	err = pipe.Walk([]string{*testWalkerPath}, done, jobs, resCh)
+	err = pipe.Walk([]string{TestWalkerPath}, done, jobs, resCh)
 	OK(t, err)
 
 	// wait for all workers to terminate
@@ -209,14 +207,14 @@ func TestPipelineWalker(t *testing.T) {
 	// wait for top-level blob
 	<-resCh
 
-	t.Logf("walked path %s with %d dirs, %d files", *testWalkerPath,
+	t.Logf("walked path %s with %d dirs, %d files", TestWalkerPath,
 		after.dirs, after.files)
 
 	Assert(t, before == after, "stats do not match, expected %v, got %v", before, after)
 }
 
 func BenchmarkPipelineWalker(b *testing.B) {
-	if *testWalkerPath == "" {
+	if TestWalkerPath == "" {
 		b.Skipf("walkerpath not set, skipping BenchPipelineWalker")
 	}
 
@@ -283,8 +281,8 @@ func BenchmarkPipelineWalker(b *testing.B) {
 		dirCh := make(chan pipe.Dir, 200)
 
 		var wg sync.WaitGroup
-		b.Logf("starting %d workers", *maxWorkers)
-		for i := 0; i < *maxWorkers; i++ {
+		b.Logf("starting %d workers", maxWorkers)
+		for i := 0; i < maxWorkers; i++ {
 			wg.Add(2)
 			go dirWorker(&wg, done, dirCh)
 			go fileWorker(&wg, done, entCh)
@@ -300,7 +298,7 @@ func BenchmarkPipelineWalker(b *testing.B) {
 		}()
 
 		resCh := make(chan pipe.Result, 1)
-		err := pipe.Walk([]string{*testWalkerPath}, done, jobs, resCh)
+		err := pipe.Walk([]string{TestWalkerPath}, done, jobs, resCh)
 		OK(b, err)
 
 		// wait for all workers to terminate
@@ -314,13 +312,13 @@ func BenchmarkPipelineWalker(b *testing.B) {
 }
 
 func TestPipelineWalkerMultiple(t *testing.T) {
-	if *testWalkerPath == "" {
+	if TestWalkerPath == "" {
 		t.Skipf("walkerpath not set, skipping TestPipelineWalker")
 	}
 
-	paths, err := filepath.Glob(filepath.Join(*testWalkerPath, "*"))
+	paths, err := filepath.Glob(filepath.Join(TestWalkerPath, "*"))
 
-	before, err := statPath(*testWalkerPath)
+	before, err := statPath(TestWalkerPath)
 	OK(t, err)
 
 	t.Logf("walking paths %v with %d dirs, %d files", paths,
@@ -371,7 +369,7 @@ func TestPipelineWalkerMultiple(t *testing.T) {
 	done := make(chan struct{})
 	jobs := make(chan pipe.Job)
 
-	for i := 0; i < *maxWorkers; i++ {
+	for i := 0; i < maxWorkers; i++ {
 		wg.Add(1)
 		go worker(&wg, done, jobs)
 	}
diff --git a/repository/repository.go b/repository/repository.go
index aad5f3c9b..491ef6bd7 100644
--- a/repository/repository.go
+++ b/repository/repository.go
@@ -372,7 +372,7 @@ func (s *Repository) SaveJSONUnpacked(t backend.Type, item interface{}) (backend
 	if err != nil {
 		return nil, err
 	}
-	debug.Log("Repo.SaveJSONUnpacked", "create new file %p", blob)
+	debug.Log("Repo.SaveJSONUnpacked", "create new blob %v", t)
 
 	// hash
 	hw := backend.NewHashingWriter(blob, sha256.New())
@@ -396,9 +396,12 @@ func (s *Repository) SaveJSONUnpacked(t backend.Type, item interface{}) (backend
 
 	err = blob.Finalize(t, sid.String())
 	if err != nil {
+		debug.Log("Repo.SaveJSONUnpacked", "error saving blob %v as %v: %v", t, sid, err)
 		return nil, err
 	}
 
+	debug.Log("Repo.SaveJSONUnpacked", "new blob %v saved as %v", t, sid)
+
 	return sid, nil
 }
 
diff --git a/repository/repository_test.go b/repository/repository_test.go
index fe9f5c9d4..7691e596a 100644
--- a/repository/repository_test.go
+++ b/repository/repository_test.go
@@ -5,7 +5,6 @@ import (
 	"crypto/rand"
 	"crypto/sha256"
 	"encoding/json"
-	"flag"
 	"io"
 	"testing"
 
@@ -15,8 +14,6 @@ import (
 	. "github.com/restic/restic/test"
 )
 
-var benchTestDir = flag.String("test.dir", ".", "dir used in benchmarks (default: .)")
-
 type testJSONStruct struct {
 	Foo uint32
 	Bar string
@@ -28,8 +25,8 @@ var repoTests = []testJSONStruct{
 }
 
 func TestSaveJSON(t *testing.T) {
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	for _, obj := range repoTests {
 		data, err := json.Marshal(obj)
@@ -47,8 +44,8 @@ func TestSaveJSON(t *testing.T) {
 }
 
 func BenchmarkSaveJSON(t *testing.B) {
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	obj := repoTests[0]
 
@@ -72,8 +69,8 @@ func BenchmarkSaveJSON(t *testing.B) {
 var testSizes = []int{5, 23, 2<<18 + 23, 1 << 20}
 
 func TestSave(t *testing.T) {
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	for _, size := range testSizes {
 		data := make([]byte, size)
@@ -104,8 +101,8 @@ func TestSave(t *testing.T) {
 }
 
 func TestSaveFrom(t *testing.T) {
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	for _, size := range testSizes {
 		data := make([]byte, size)
@@ -134,8 +131,8 @@ func TestSaveFrom(t *testing.T) {
 }
 
 func BenchmarkSaveFrom(t *testing.B) {
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	size := 4 << 20 // 4MiB
 
@@ -156,15 +153,15 @@ func BenchmarkSaveFrom(t *testing.B) {
 }
 
 func TestLoadJSONPack(t *testing.T) {
-	if *benchTestDir == "" {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	if BenchArchiveDirectory == "" {
 		t.Skip("benchdir not set, skipping")
 	}
 
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
-
 	// archive a few files
-	sn := SnapshotDir(t, repo, *benchTestDir, nil)
+	sn := SnapshotDir(t, repo, BenchArchiveDirectory, nil)
 	OK(t, repo.Flush())
 
 	tree := restic.NewTree()
@@ -173,13 +170,13 @@ func TestLoadJSONPack(t *testing.T) {
 }
 
 func TestLoadJSONUnpacked(t *testing.T) {
-	if *benchTestDir == "" {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	if BenchArchiveDirectory == "" {
 		t.Skip("benchdir not set, skipping")
 	}
 
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
-
 	// archive a snapshot
 	sn := restic.Snapshot{}
 	sn.Hostname = "foobar"
diff --git a/snapshot_test.go b/snapshot_test.go
index 00bb7a038..649e9a1f4 100644
--- a/snapshot_test.go
+++ b/snapshot_test.go
@@ -8,9 +8,6 @@ import (
 )
 
 func TestNewSnapshot(t *testing.T) {
-	s := SetupRepo(t)
-	defer TeardownRepo(t, s)
-
 	paths := []string{"/home/foobar"}
 
 	_, err := restic.NewSnapshot(paths)
diff --git a/test/backend.go b/test/backend.go
index bcf874c0f..c2d1fe285 100644
--- a/test/backend.go
+++ b/test/backend.go
@@ -14,12 +14,13 @@ import (
 )
 
 var (
-	TestPassword       = getStringVar("RESTIC_TEST_PASSWORD", "geheim")
-	TestCleanup        = getBoolVar("RESTIC_TEST_CLEANUP", true)
-	TestTempDir        = getStringVar("RESTIC_TEST_TMPDIR", "")
-	RunIntegrationTest = getBoolVar("RESTIC_TEST_INTEGRATION", true)
-	TestSFTPPath       = getStringVar("RESTIC_TEST_SFTPPATH",
-		"/usr/lib/ssh:/usr/lib/openssh")
+	TestPassword          = getStringVar("RESTIC_TEST_PASSWORD", "geheim")
+	TestCleanup           = getBoolVar("RESTIC_TEST_CLEANUP", true)
+	TestTempDir           = getStringVar("RESTIC_TEST_TMPDIR", "")
+	RunIntegrationTest    = getBoolVar("RESTIC_TEST_INTEGRATION", true)
+	TestSFTPPath          = getStringVar("RESTIC_TEST_SFTPPATH", "/usr/lib/ssh:/usr/lib/openssh")
+	TestWalkerPath        = getStringVar("RESTIC_TEST_PATH", ".")
+	BenchArchiveDirectory = getStringVar("RESTIC_BENCH_DIR", ".")
 )
 
 func getStringVar(name, defaultValue string) string {
@@ -45,27 +46,38 @@ func getBoolVar(name string, defaultValue bool) bool {
 	return defaultValue
 }
 
-func SetupRepo(t testing.TB) *repository.Repository {
+func SetupRepo() *repository.Repository {
 	tempdir, err := ioutil.TempDir(TestTempDir, "restic-test-")
-	OK(t, err)
+	if err != nil {
+		panic(err)
+	}
 
 	// create repository below temp dir
 	b, err := local.Create(filepath.Join(tempdir, "repo"))
-	OK(t, err)
+	if err != nil {
+		panic(err)
+	}
 
 	repo := repository.New(b)
-	OK(t, repo.Init(TestPassword))
+	err = repo.Init(TestPassword)
+	if err != nil {
+		panic(err)
+	}
+
 	return repo
 }
 
-func TeardownRepo(t testing.TB, repo *repository.Repository) {
+func TeardownRepo(repo *repository.Repository) {
 	if !TestCleanup {
 		l := repo.Backend().(*local.Local)
-		t.Logf("leaving local backend at %s\n", l.Location())
+		fmt.Printf("leaving local backend at %s\n", l.Location())
 		return
 	}
 
-	OK(t, repo.Delete())
+	err := repo.Delete()
+	if err != nil {
+		panic(err)
+	}
 }
 
 func SnapshotDir(t testing.TB, repo *repository.Repository, path string, parent backend.ID) *restic.Snapshot {
@@ -74,3 +86,9 @@ func SnapshotDir(t testing.TB, repo *repository.Repository, path string, parent
 	OK(t, err)
 	return sn
 }
+
+func WithRepo(t testing.TB, f func(*repository.Repository)) {
+	repo := SetupRepo()
+	f(repo)
+	TeardownRepo(repo)
+}
diff --git a/tree_test.go b/tree_test.go
index b46f01b0a..2d9cb7b7e 100644
--- a/tree_test.go
+++ b/tree_test.go
@@ -93,8 +93,8 @@ func TestNodeComparison(t *testing.T) {
 }
 
 func TestLoadTree(t *testing.T) {
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
 	// save tree
 	tree := restic.NewTree()
diff --git a/walk_test.go b/walk_test.go
index 384e605df..397655978 100644
--- a/walk_test.go
+++ b/walk_test.go
@@ -1,7 +1,6 @@
 package restic_test
 
 import (
-	"flag"
 	"path/filepath"
 	"testing"
 
@@ -10,14 +9,12 @@ import (
 	. "github.com/restic/restic/test"
 )
 
-var testWalkDirectory = flag.String("test.walkdir", ".", "test walking a directory (globbing pattern, default: .)")
-
 func TestWalkTree(t *testing.T) {
-	dirs, err := filepath.Glob(*testWalkDirectory)
-	OK(t, err)
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
 
-	repo := SetupRepo(t)
-	defer TeardownRepo(t, repo)
+	dirs, err := filepath.Glob(TestWalkerPath)
+	OK(t, err)
 
 	// archive a few files
 	arch := restic.NewArchiver(repo)