diff --git a/include/dwarfs/scanner.h b/include/dwarfs/scanner.h
index acf0db27..f2a01022 100644
--- a/include/dwarfs/scanner.h
+++ b/include/dwarfs/scanner.h
@@ -43,9 +43,8 @@ class thread_pool;
 
 class scanner {
  public:
-  scanner(logger& lgr, thread_pool& pool, std::shared_ptr<segmenter_factory> sf,
-          std::shared_ptr<entry_factory> ef,
-          std::shared_ptr<os_access const> os, std::shared_ptr<script> scr,
+  scanner(logger& lgr, thread_pool& pool, segmenter_factory& sf,
+          entry_factory& ef, os_access const& os, std::shared_ptr<script> scr,
           const scanner_options& options);
 
   void scan(
diff --git a/src/dwarfs/scanner.cpp b/src/dwarfs/scanner.cpp
index 48b5eace..f376988d 100644
--- a/src/dwarfs/scanner.cpp
+++ b/src/dwarfs/scanner.cpp
@@ -289,9 +289,8 @@ std::string status_string(progress const& p, size_t width) {
 template <typename LoggerPolicy>
 class scanner_ final : public scanner::impl {
  public:
-  scanner_(logger& lgr, worker_group& wg, std::shared_ptr<segmenter_factory> sf,
-           std::shared_ptr<entry_factory> ef,
-           std::shared_ptr<os_access const> os, std::shared_ptr<script> scr,
+  scanner_(logger& lgr, worker_group& wg, segmenter_factory& sf,
+           entry_factory& ef, os_access const& os, std::shared_ptr<script> scr,
            const scanner_options& options);
 
   void scan(filesystem_writer& fsw, std::filesystem::path const& path,
@@ -318,26 +317,25 @@ class scanner_ final : public scanner::impl {
   LOG_PROXY_DECL(LoggerPolicy);
   worker_group& wg_;
   scanner_options const& options_;
-  std::shared_ptr<segmenter_factory> segmenter_factory_;
-  std::shared_ptr<entry_factory> entry_factory_;
-  std::shared_ptr<os_access const> os_;
+  segmenter_factory& segmenter_factory_;
+  entry_factory& entry_factory_;
+  os_access const& os_;
   std::shared_ptr<script> script_;
 };
 
 template <typename LoggerPolicy>
 scanner_<LoggerPolicy>::scanner_(logger& lgr, worker_group& wg,
-                                 std::shared_ptr<segmenter_factory> sf,
-                                 std::shared_ptr<entry_factory> ef,
-                                 std::shared_ptr<os_access const> os,
+                                 segmenter_factory& sf, entry_factory& ef,
+                                 os_access const& os,
                                  std::shared_ptr<script> scr,
                                  const scanner_options& options)
     : LOG_PROXY_INIT(lgr)
     , wg_{wg}
     , options_{options}
-    , segmenter_factory_{std::move(sf)}
-    , entry_factory_{std::move(ef)}
-    , os_(std::move(os))
-    , script_(std::move(scr)) {}
+    , segmenter_factory_{sf}
+    , entry_factory_{ef}
+    , os_{os}
+    , script_{std::move(scr)} {}
 
 template <typename LoggerPolicy>
 std::shared_ptr<entry>
@@ -345,7 +343,7 @@ scanner_<LoggerPolicy>::add_entry(std::filesystem::path const& name,
                                   std::shared_ptr<dir> parent, progress& prog,
                                   file_scanner& fs, bool debug_filter) {
   try {
-    auto pe = entry_factory_->create(*os_, name, parent);
+    auto pe = entry_factory_.create(os_, name, parent);
     bool exclude = false;
 
     if (script_) {
@@ -371,7 +369,7 @@ scanner_<LoggerPolicy>::add_entry(std::filesystem::path const& name,
     if (pe) {
       switch (pe->type()) {
       case entry::E_FILE:
-        if (pe->size() > 0 && os_->access(pe->fs_path(), R_OK)) {
+        if (pe->size() > 0 && os_.access(pe->fs_path(), R_OK)) {
           LOG_ERROR << "cannot access " << pe->path_as_string()
                     << ", creating empty file";
           pe->override_size(0);
@@ -402,7 +400,7 @@ scanner_<LoggerPolicy>::add_entry(std::filesystem::path const& name,
         // prog.current.store(pe.get());
         prog.dirs_found++;
         if (!debug_filter) {
-          pe->scan(*os_, prog);
+          pe->scan(os_, prog);
         }
         break;
 
@@ -416,7 +414,7 @@ scanner_<LoggerPolicy>::add_entry(std::filesystem::path const& name,
       case entry::E_LINK:
         prog.symlinks_found++;
         if (!debug_filter) {
-          pe->scan(*os_, prog);
+          pe->scan(os_, prog);
         }
         prog.symlinks_scanned++;
         break;
@@ -425,7 +423,7 @@ scanner_<LoggerPolicy>::add_entry(std::filesystem::path const& name,
       case entry::E_OTHER:
         prog.specials_found++;
         if (!debug_filter) {
-          pe->scan(*os_, prog);
+          pe->scan(os_, prog);
         }
         break;
 
@@ -450,7 +448,7 @@ void scanner_<LoggerPolicy>::dump_state(
     std::string_view env_var, std::string_view what,
     std::shared_ptr<file_access const> fa,
     std::function<void(std::ostream&)> dumper) const {
-  if (auto dumpfile = os_->getenv(env_var)) {
+  if (auto dumpfile = os_.getenv(env_var)) {
     if (fa) {
       LOG_VERBOSE << "dumping " << what << " to " << *dumpfile;
       std::error_code ec;
@@ -474,7 +472,7 @@ template <typename LoggerPolicy>
 std::shared_ptr<entry>
 scanner_<LoggerPolicy>::scan_tree(std::filesystem::path const& path,
                                   progress& prog, file_scanner& fs) {
-  auto root = entry_factory_->create(*os_, path);
+  auto root = entry_factory_.create(os_, path);
   bool const debug_filter = options_.debug_filter_function.has_value();
 
   if (root->type() != entry::E_DIR) {
@@ -498,7 +496,7 @@ scanner_<LoggerPolicy>::scan_tree(std::filesystem::path const& path,
     auto ppath = parent->fs_path();
 
     try {
-      auto d = os_->opendir(ppath);
+      auto d = os_.opendir(ppath);
       std::filesystem::path name;
       std::vector<std::shared_ptr<entry>> subdirs;
 
@@ -534,7 +532,7 @@ scanner_<LoggerPolicy>::scan_list(std::filesystem::path const& path,
 
   auto ti = LOG_TIMED_INFO;
 
-  auto root = entry_factory_->create(*os_, path);
+  auto root = entry_factory_.create(os_, path);
 
   if (root->type() != entry::E_DIR) {
     DWARFS_THROW(runtime_error,
@@ -619,10 +617,10 @@ void scanner_<LoggerPolicy>::scan(
   prog.set_status_function(status_string);
 
   inode_manager im(LOG_GET_LOGGER, prog, options_.inode);
-  file_scanner fs(LOG_GET_LOGGER, wg_, *os_, im, prog,
+  file_scanner fs(LOG_GET_LOGGER, wg_, os_, im, prog,
                   {.hash_algo = options_.file_hash_algorithm,
-                   .debug_inode_create = os_->getenv(kEnvVarDumpFilesRaw) ||
-                                         os_->getenv(kEnvVarDumpFilesFinal)});
+                   .debug_inode_create = os_.getenv(kEnvVarDumpFilesRaw) ||
+                                         os_.getenv(kEnvVarDumpFilesFinal)});
 
   auto root =
       list ? scan_list(path, *list, prog, fs) : scan_tree(path, prog, fs);
@@ -668,7 +666,7 @@ void scanner_<LoggerPolicy>::scan(
   // the file vectors are populated
   if (im.has_invalid_inodes()) {
     LOG_INFO << "trying to recover any invalid inodes...";
-    im.try_scan_invalid(wg_, *os_);
+    im.try_scan_invalid(wg_, os_);
     wg_.wait();
   }
 
@@ -738,8 +736,8 @@ void scanner_<LoggerPolicy>::scan(
 
   {
     size_t const num_threads = options_.num_segmenter_workers;
-    worker_group wg_ordering(LOG_GET_LOGGER, *os_, "ordering", num_threads);
-    worker_group wg_blockify(LOG_GET_LOGGER, *os_, "blockify", num_threads);
+    worker_group wg_ordering(LOG_GET_LOGGER, os_, "ordering", num_threads);
+    worker_group wg_blockify(LOG_GET_LOGGER, os_, "blockify", num_threads);
 
     fsw.configure(frag_info.categories, num_threads);
 
@@ -763,7 +761,7 @@ void scanner_<LoggerPolicy>::scan(
         auto span = im.ordered_span(category, wg_ordering);
         auto tv = LOG_CPU_TIMED_VERBOSE;
 
-        auto seg = segmenter_factory_->create(
+        auto seg = segmenter_factory_.create(
             category, cat_size, cc, blockmgr,
             [category, meta, blockmgr, &fsw](auto block,
                                              auto logical_block_num) {
@@ -785,7 +783,7 @@ void scanner_<LoggerPolicy>::scan(
           auto f = ino->any();
 
           if (auto size = f->size(); size > 0 && !f->is_invalid()) {
-            auto [mm, _, errors] = ino->mmap_any(*os_);
+            auto [mm, _, errors] = ino->mmap_any(os_);
 
             if (mm) {
               file_off_t offset{0};
@@ -947,7 +945,7 @@ void scanner_<LoggerPolicy>::scan(
   mv2.gids() = ge_data.get_gids();
   mv2.modes() = ge_data.get_modes();
   mv2.timestamp_base() = ge_data.get_timestamp_base();
-  mv2.block_size() = segmenter_factory_->get_block_size();
+  mv2.block_size() = segmenter_factory_.get_block_size();
   mv2.total_fs_size() = prog.original_size;
   mv2.total_hardlink_size() = prog.hardlink_size;
   mv2.options() = fsopts;
@@ -1012,14 +1010,12 @@ void scanner_<LoggerPolicy>::scan(
 
 } // namespace internal
 
-scanner::scanner(logger& lgr, thread_pool& pool,
-                 std::shared_ptr<segmenter_factory> sf,
-                 std::shared_ptr<entry_factory> ef,
-                 std::shared_ptr<os_access const> os,
+scanner::scanner(logger& lgr, thread_pool& pool, segmenter_factory& sf,
+                 entry_factory& ef, os_access const& os,
                  std::shared_ptr<script> scr, const scanner_options& options)
     : impl_(
           make_unique_logging_object<impl, internal::scanner_, logger_policies>(
-              lgr, pool.get_worker_group(), std::move(sf), std::move(ef),
-              std::move(os), std::move(scr), options)) {}
+              lgr, pool.get_worker_group(), sf, ef, os, std::move(scr),
+              options)) {}
 
 } // namespace dwarfs
diff --git a/src/mkdwarfs_main.cpp b/src/mkdwarfs_main.cpp
index c7409d39..3274f6f5 100644
--- a/src/mkdwarfs_main.cpp
+++ b/src/mkdwarfs_main.cpp
@@ -1274,7 +1274,7 @@ int mkdwarfs_main(int argc, sys_char** argv, iolayer const& iol) {
                             std::numeric_limits<size_t>::max(),
                             compress_niceness);
 
-  std::unique_ptr<filesystem_writer> fsw;
+  std::optional<filesystem_writer> fsw;
 
   try {
     std::ostream& fsw_os =
@@ -1285,9 +1285,8 @@ int mkdwarfs_main(int argc, sys_char** argv, iolayer const& iol) {
               },
               [&](std::ostringstream& oss) -> std::ostream& { return oss; }};
 
-    fsw = std::make_unique<filesystem_writer>(
-        fsw_os, lgr, compress_pool, prog, schema_bc, metadata_bc, history_bc,
-        fswopts, header_ifs ? &header_ifs->is() : nullptr);
+    fsw.emplace(fsw_os, lgr, compress_pool, prog, schema_bc, metadata_bc,
+                history_bc, fswopts, header_ifs ? &header_ifs->is() : nullptr);
 
     categorized_option<block_compressor> compression_opt;
     contextual_option_parser cop("--compression", compression_opt, cp,
@@ -1343,15 +1342,12 @@ int mkdwarfs_main(int argc, sys_char** argv, iolayer const& iol) {
       input_filesystem->rewrite(prog, *fsw, *cat_resolver, rw_opts);
       compress_pool.wait();
     } else {
-      auto sf = std::make_shared<segmenter_factory>(
-          lgr, prog, options.inode.categorizer_mgr, sf_config);
-
-      auto ef = std::make_shared<entry_factory>();
+      segmenter_factory sf(lgr, prog, options.inode.categorizer_mgr, sf_config);
+      entry_factory ef;
 
       thread_pool scanner_pool(lgr, *iol.os, "scanner", num_scanner_workers);
 
-      scanner s(lgr, scanner_pool, std::move(sf), std::move(ef), iol.os,
-                std::move(script), options);
+      scanner s(lgr, scanner_pool, sf, ef, *iol.os, std::move(script), options);
 
       s.scan(*fsw, path, prog, input_list, iol.file);
 
diff --git a/test/dwarfs_benchmark.cpp b/test/dwarfs_benchmark.cpp
index a0bf3106..1b53812e 100644
--- a/test/dwarfs_benchmark.cpp
+++ b/test/dwarfs_benchmark.cpp
@@ -123,10 +123,10 @@ std::string make_filesystem(::benchmark::State const& state) {
   thread_pool pool(lgr, *os, "writer", 4);
   writer_progress prog;
 
-  auto sf = std::make_shared<segmenter_factory>(lgr, prog, cfg);
-  auto ef = std::make_shared<entry_factory>();
+  segmenter_factory sf(lgr, prog, cfg);
+  entry_factory ef;
 
-  scanner s(lgr, pool, sf, ef, os, std::make_shared<test::script_mock>(),
+  scanner s(lgr, pool, sf, ef, *os, std::make_shared<test::script_mock>(),
             options);
 
   std::ostringstream oss;
diff --git a/test/dwarfs_test.cpp b/test/dwarfs_test.cpp
index 25ee1d1e..6c94d883 100644
--- a/test/dwarfs_test.cpp
+++ b/test/dwarfs_test.cpp
@@ -94,10 +94,10 @@ build_dwarfs(logger& lgr, std::shared_ptr<test::os_access_mock> input,
   sf_cfg.max_active_blocks.set_default(cfg.max_active_blocks);
   sf_cfg.bloom_filter_size.set_default(cfg.bloom_filter_size);
 
-  auto sf = std::make_shared<segmenter_factory>(lgr, *prog, sf_cfg);
-  auto ef = std::make_shared<entry_factory>();
+  segmenter_factory sf(lgr, *prog, sf_cfg);
+  entry_factory ef;
 
-  scanner s(lgr, pool, sf, ef, input, scr, options);
+  scanner s(lgr, pool, sf, ef, *input, scr, options);
 
   std::ostringstream oss;
 
@@ -937,10 +937,9 @@ class filter_test
 
     writer_progress prog;
     thread_pool pool(lgr, *input, "worker", 1);
-    auto sf = std::make_shared<segmenter_factory>(lgr, prog,
-                                                  segmenter_factory::config{});
-    auto ef = std::make_shared<entry_factory>();
-    scanner s(lgr, pool, sf, ef, input, scr, options);
+    segmenter_factory sf(lgr, prog, segmenter_factory::config{});
+    entry_factory ef;
+    scanner s(lgr, pool, sf, ef, *input, scr, options);
 
     block_compressor bc("null");
     std::ostringstream null;