diff --git a/mongoose.c b/mongoose.c
index 9c086aa1..b1fd2dbb 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -1555,7 +1555,6 @@ void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
     // Received headers - check authentication and possibly start uploads/ota
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     struct mg_dash_user *u = mg_dash_authenticate(c, hm, dash);
-
     if (mg_match(hm->uri, mg_str("/api/hi"), NULL) ||
         mg_match(hm->uri, mg_str("/api/logout"), NULL)) {
       // Do nothing, handle them MG_EV_HTTP_MSG. We bypass auth for those
@@ -1628,7 +1627,7 @@ void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
           break;
         }
       }
-      if (ch == NULL) mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found");
+      if (ch == NULL) mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found\n");
       mg_log_http_req(c, hm);
     }
   }
@@ -2855,6 +2854,7 @@ size_t mg_vxprintf(void (*out)(char, void *), void *param, const char *fmt,
 
 
 
+
 struct mg_fd *mg_fs_open(struct mg_fs *fs, const char *path, int flags) {
   struct mg_fd *fd = (struct mg_fd *) mg_calloc(1, sizeof(*fd));
   if (fd != NULL) {
@@ -2899,6 +2899,7 @@ bool mg_file_write(struct mg_fs *fs, const char *path, const void *buf,
   char tmp[MG_PATH_MAX], rnd[10];
   size_t path_len = mg_snprintf(tmp, sizeof(tmp), "%s..%s", path,
                                 mg_random_str(rnd, sizeof(rnd)));
+  fs->rm(tmp);
   if (path_len < sizeof(tmp) &&
       (fd = mg_fs_open(fs, tmp, MG_FS_WRITE | MG_FS_EXCL)) != NULL) {
     result = fs->wr(fd->fd, buf, len) == len;
@@ -2906,8 +2907,11 @@ bool mg_file_write(struct mg_fs *fs, const char *path, const void *buf,
     if (result) {
       fs->rm(path);
       result = fs->mv(tmp, path);
+      MG_DEBUG(("mv %s -> %s result=%d", tmp, path, result));
     }
     fs->rm(tmp);
+  } else {
+    MG_ERROR(("mg_fs_open(%s) failed, path_len=%zu", tmp, path_len));
   }
   return result;
 }
@@ -3209,6 +3213,10 @@ struct mg_fs mg_fs_packed = {
 #define MG_STAT_FUNC stat
 #endif
 
+#if MG_ENABLE_LFS
+#include <dirent.h>
+#endif
+
 static int p_stat(const char *path, size_t *size, time_t *mtime) {
 #if !defined(S_ISDIR)
   MG_ERROR(("stat() API is not supported. %p %p %p", path, size, mtime));
@@ -3360,7 +3368,6 @@ struct dirent *readdir(DIR *d) {
 
 static void p_list(const char *dir, void (*fn)(const char *, void *),
                    void *userdata) {
-#if MG_ENABLE_DIRLIST
   struct dirent *dp;
   DIR *dirp;
   if ((dirp = (opendir(dir))) == NULL) return;
@@ -3369,9 +3376,6 @@ static void p_list(const char *dir, void (*fn)(const char *, void *),
     fn(dp->d_name, userdata);
   }
   closedir(dirp);
-#else
-  (void) dir, (void) fn, (void) userdata;
-#endif
 }
 
 static void *p_open(const char *path, int flags) {
@@ -6362,18 +6366,17 @@ bool mg_l2_pppoe_rx(struct mg_tcpip_if *ifp, enum mg_l2proto *proto,
 
 
 
-#if MG_ENABLE_LFS
 
-#include <fcntl.h>
-#include <littlefs/lfs.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <sys/types.h>
+#if MG_ENABLE_LFS
 
 #ifndef LFS_USE_RAM
 #define LFS_USE_RAM 0  // If 1, use RAM FS. If 0, use flash
 #endif
 
+#ifndef MG_LFS_SIZE
+#define MG_LFS_SIZE (64 * 1024)
+#endif
+
 #ifndef MG_LFS_BUF_SIZE
 #define MG_LFS_BUF_SIZE 64  // Buffer size used for reads, writes, and cache
 #endif
@@ -6386,19 +6389,6 @@ bool mg_l2_pppoe_rx(struct mg_tcpip_if *ifp, enum mg_l2proto *proto,
 #define MG_LFS_BLOCK_SIZE 8192
 #endif
 
-#ifndef DT_DIR
-#define DT_DIR 4
-#endif
-#ifndef DT_REG
-#define DT_REG 8
-#endif
-
-typedef struct mg_lfs_fd DIR;
-struct dirent {
-  char d_name[LFS_NAME_MAX + 1];
-  unsigned char d_type;
-};
-
 struct mg_lfs_fd {
   struct mg_lfs_fd *next;
   bool isopen;
@@ -6468,29 +6458,50 @@ static int lfs_driver_sync(const struct lfs_config *cfg) {
 }
 
 bool mg_lfs_init(size_t size) {
-  int result = 0;
+  //bool ok = false;
+  MG_DEBUG(("size: %zu", size));
   if (s_lfs_ready) return true;
-  if (size == 0) return false;
+  if (size == 0) {
+    MG_ERROR(("invalidsize = 0"));
+  } else {
 #if LFS_USE_RAM
-  s_cfg.block_size = MG_LFS_BLOCK_SIZE;
-  if (s_ram_fs == NULL) s_ram_fs = (uint8_t *) mg_calloc(1, size);
-  s_fs = s_ram_fs;
+    s_cfg.block_size = MG_LFS_BLOCK_SIZE;
+    if (s_ram_fs == NULL) s_ram_fs = (uint8_t *) mg_calloc(1, size);
+    s_fs = s_ram_fs;
 #else
-  if (mg_flash == NULL || mg_flash->secsz == 0 || mg_flash->size < size) return false;
-  if (mg_flash->write_fn == NULL) return false;
-  s_cfg.block_size = mg_flash->secsz;
-  s_fs = (uint8_t *) mg_flash->start + mg_flash->size - size;
+    {
+      // Some flash attributes may be initialised on ota_begin
+      int lev = mg_log_level;
+      mg_log_level = MG_LL_NONE;
+      mg_ota_begin(1);
+      mg_ota_end();
+      mg_log_set(lev);
+    }
+    if (mg_flash == NULL || mg_flash->secsz == 0 || mg_flash->size < size) {
+      MG_ERROR(("mg_flash %p secsz %zu flash_size %zu < size %zu", mg_flash, mg_flash->secsz, mg_flash->size, size));
+    } else if (mg_flash->write_fn == NULL) {
+      MG_ERROR(("flash write_fn == NULL"));
+    } else {
+      s_cfg.block_size = mg_flash->secsz;
+      s_fs = (uint8_t *) mg_flash->start + mg_flash->size - size;
+    }
 #endif
-  if (s_fs == NULL || s_cfg.block_size == 0 || size % s_cfg.block_size != 0) {
-    return false;
+    if (s_fs == NULL || s_cfg.block_size == 0 || size % s_cfg.block_size != 0) {
+      MG_ERROR(("s_fs %p blk_size %zu size %zu", s_fs, s_cfg.block_size));
+    } else {
+      s_cfg.block_count = (lfs_size_t) (size / s_cfg.block_size);
+      if (s_cfg.block_count == 0) {
+        MG_ERROR(("blk_count == 0"));
+      } else {
+        if (lfs_mount(&s_lfs, &s_cfg) != 0) lfs_format(&s_lfs, &s_cfg);
+        if (lfs_mount(&s_lfs, &s_cfg) != 0) {
+          MG_ERROR(("lfs_mount"));
+        } else {
+          s_lfs_ready = true;
+        }
+      }
+    }
   }
-  s_cfg.block_count = (lfs_size_t) (size / s_cfg.block_size);
-  if (s_cfg.block_count == 0) return false;
-  if (lfs_mount(&s_lfs, &s_cfg) != 0) {
-    lfs_format(&s_lfs, &s_cfg);
-    if (lfs_mount(&s_lfs, &s_cfg) != 0) result = -1;
-  }
-  s_lfs_ready = result == 0;
   return s_lfs_ready;
 }
 
@@ -6504,6 +6515,7 @@ static struct mg_lfs_fd *find_fd(int fd) {
 
 static struct mg_lfs_fd *open_fd(void) {
   struct mg_lfs_fd *f = NULL;
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   if (s_lfs_ready) {
     f = (struct mg_lfs_fd *) mg_calloc(1, sizeof(*f));
     if (f != NULL) {
@@ -6531,6 +6543,7 @@ int _open(const char *path, int flags, mode_t mode) {
   int err, lfs_flags = 0, fd = -1;
   struct mg_lfs_fd *f = open_fd();
   (void) mode;
+  MG_DEBUG(("%s -> %p, lfs_ready %d", path, f, s_lfs_ready));
   if (f == NULL) return -1;
   fd = f->fd;
   if ((flags & 3) == O_RDONLY) lfs_flags |= LFS_O_RDONLY;
@@ -6572,11 +6585,21 @@ int _lseek(int fd, int offset, int whence) {
 }
 
 int _rename(const char *oldname, const char *newname) {
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   return s_lfs_ready ? lfs_rename(&s_lfs, oldname, newname) : -1;
 }
 
-int _unlink_r(void *r, const char *a) {
-  (void) r;
+// Some libc rename() implementations have no atomic rename syscall and emulate
+// it as link() + unlink() instead of calling _rename() directly. LittleFS has
+// no real hard links, but forwarding to _rename() gives the same end result
+// (oldname becomes newname), which is all mg_file_write()'s atomic-write
+// pattern (write to a temp file, then rename it into place) needs
+int _link(const char *oldname, const char *newname) {
+  return _rename(oldname, newname);
+}
+
+int _unlink(const char *a) {
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   return s_lfs_ready ? lfs_remove(&s_lfs, a) : -1;
 }
 
@@ -6585,7 +6608,7 @@ DIR *opendir(const char *name) {
   if (f == NULL) return NULL;
   if (lfs_dir_open(&s_lfs, &f->dir, name) != 0) {
     close_fd(f);
-    return NULL;
+    f = NULL;
   }
   return (DIR *) f;
 }
@@ -6612,7 +6635,9 @@ struct dirent *readdir(DIR *dir) {
 
 int _stat(const char *path, struct stat *st) {
   struct lfs_info info;
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   if (!s_lfs_ready || lfs_stat(&s_lfs, path, &info) != 0) return -1;
+  memset(st, 0, sizeof(*st));
   st->st_mode = info.type == LFS_TYPE_DIR ? S_IFDIR : S_IFREG;
   st->st_size = info.size;
   return 0;
@@ -6626,9 +6651,9 @@ int _fstat(int fd, struct stat *st) {
 
 int mkdir(const char *path, mode_t mode) {
   (void) mode;
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   return s_lfs_ready ? lfs_mkdir(&s_lfs, path) : -1;
 }
-
 #endif
 
 #ifdef MG_ENABLE_LINES
diff --git a/mongoose.h b/mongoose.h
index 99e4e992..f1d02ed3 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -103,8 +103,9 @@ extern "C" {
 #include <sys/types.h>
 #include <time.h>
 
+#ifndef MG_PATH_MAX
 #define MG_PATH_MAX 100
-#define MG_ENABLE_DIRLIST 0
+#endif
 
 #endif
 
@@ -127,8 +128,9 @@ extern "C" {
 #include <time.h>
 #include <unistd.h>
 
+#ifndef MG_PATH_MAX
 #define MG_PATH_MAX 100
-#define MG_ENABLE_DIRLIST 0
+#endif
 
 #endif
 
@@ -158,10 +160,6 @@ extern "C" {
 #define MG_PATH_MAX 100
 #endif
 
-#ifndef MG_ENABLE_DIRLIST
-#define MG_ENABLE_DIRLIST 0
-#endif
-
 
 #ifndef MG_ENABLE_TCPIP
 #define MG_ENABLE_TCPIP 1  // Enable built-in TCP/IP stack
@@ -1364,7 +1362,7 @@ struct timeval {
 #endif
 
 #ifndef MG_ENABLE_DIRLIST
-#define MG_ENABLE_DIRLIST 0
+#define MG_ENABLE_DIRLIST MG_ENABLE_LFS
 #endif
 
 #ifndef MG_ENABLE_CUSTOM_RANDOM
@@ -1416,7 +1414,7 @@ struct timeval {
 #endif
 
 #ifndef MG_ENABLE_POSIX_FS
-#define MG_ENABLE_POSIX_FS 0
+#define MG_ENABLE_POSIX_FS MG_ENABLE_LFS
 #endif
 
 #ifndef MG_INVALID_SOCKET
@@ -1929,6 +1927,7 @@ void mg_timer_poll(struct mg_timer **head, uint64_t new_ms);
 
 
 
+
 // Flags returned by mg_fs.st() and passed to mg_fs.open().
 enum { MG_FS_READ = 1, MG_FS_WRITE = 2, MG_FS_DIR = 4, MG_FS_EXCL = 8 };
 
@@ -1966,6 +1965,7 @@ void mg_fs_close(struct mg_fd *fd);
 
 // Sequential directory iterator. Call repeatedly with the same buf/len;
 // each call fills buf with the next entry name. Returns false when done.
+// Note: make sure buf[0] == 0 before the first call
 bool mg_fs_ls(struct mg_fs *fs, const char *path, char *buf, size_t len);
 
 // Reads the entire file into a heap-allocated buffer. The returned mg_str is
@@ -2005,6 +2005,26 @@ struct mg_str mg_unpacked(const char *path);
 extern const struct mg_mem_file mg_packed_files[];
 
 
+#if MG_ENABLE_LFS
+#include <fcntl.h>
+#include <littlefs/lfs.h>
+
+#ifndef DT_DIR
+#define DT_DIR 4
+#endif
+#ifndef DT_REG
+#define DT_REG 8
+#endif
+
+struct dirent {
+  char d_name[LFS_NAME_MAX + 1];
+  unsigned char d_type;
+};
+
+typedef struct mg_lfs_fd  DIR;
+#endif
+
+
 
 
 
diff --git a/src/arch_armcgt.h b/src/arch_armcgt.h
index 100d5da3..a582aa1d 100644
--- a/src/arch_armcgt.h
+++ b/src/arch_armcgt.h
@@ -12,7 +12,8 @@
 #include <sys/types.h>
 #include <time.h>
 
+#ifndef MG_PATH_MAX
 #define MG_PATH_MAX 100
-#define MG_ENABLE_DIRLIST 0
+#endif
 
 #endif
diff --git a/src/arch_armgcc.h b/src/arch_armgcc.h
index cd2ffee4..d9aff5e5 100644
--- a/src/arch_armgcc.h
+++ b/src/arch_armgcc.h
@@ -18,7 +18,8 @@
 #include <time.h>
 #include <unistd.h>
 
+#ifndef MG_PATH_MAX
 #define MG_PATH_MAX 100
-#define MG_ENABLE_DIRLIST 0
+#endif
 
 #endif
diff --git a/src/arch_cube.h b/src/arch_cube.h
index 5b9f9250..6a69701e 100644
--- a/src/arch_cube.h
+++ b/src/arch_cube.h
@@ -25,10 +25,6 @@
 #define MG_PATH_MAX 100
 #endif
 
-#ifndef MG_ENABLE_DIRLIST
-#define MG_ENABLE_DIRLIST 0
-#endif
-
 
 #ifndef MG_ENABLE_TCPIP
 #define MG_ENABLE_TCPIP 1  // Enable built-in TCP/IP stack
diff --git a/src/config.h b/src/config.h
index 3681f524..f45b7b4b 100644
--- a/src/config.h
+++ b/src/config.h
@@ -83,7 +83,7 @@
 #endif
 
 #ifndef MG_ENABLE_DIRLIST
-#define MG_ENABLE_DIRLIST 0
+#define MG_ENABLE_DIRLIST MG_ENABLE_LFS
 #endif
 
 #ifndef MG_ENABLE_CUSTOM_RANDOM
@@ -135,7 +135,7 @@
 #endif
 
 #ifndef MG_ENABLE_POSIX_FS
-#define MG_ENABLE_POSIX_FS 0
+#define MG_ENABLE_POSIX_FS MG_ENABLE_LFS
 #endif
 
 #ifndef MG_INVALID_SOCKET
diff --git a/src/dash.c b/src/dash.c
index cb7cc83c..d17a66e1 100644
--- a/src/dash.c
+++ b/src/dash.c
@@ -580,7 +580,6 @@ void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
     // Received headers - check authentication and possibly start uploads/ota
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     struct mg_dash_user *u = mg_dash_authenticate(c, hm, dash);
-
     if (mg_match(hm->uri, mg_str("/api/hi"), NULL) ||
         mg_match(hm->uri, mg_str("/api/logout"), NULL)) {
       // Do nothing, handle them MG_EV_HTTP_MSG. We bypass auth for those
@@ -653,7 +652,7 @@ void mg_dash_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
           break;
         }
       }
-      if (ch == NULL) mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found");
+      if (ch == NULL) mg_http_reply(c, 404, MG_JSON_HEADERS, "Not Found\n");
       mg_log_http_req(c, hm);
     }
   }
diff --git a/src/fs.c b/src/fs.c
index 6df00c4a..7d67d102 100644
--- a/src/fs.c
+++ b/src/fs.c
@@ -1,4 +1,5 @@
 #include "fs.h"
+#include "log.h"
 #include "printf.h"
 #include "str.h"
 #include "util.h"
@@ -47,6 +48,7 @@ bool mg_file_write(struct mg_fs *fs, const char *path, const void *buf,
   char tmp[MG_PATH_MAX], rnd[10];
   size_t path_len = mg_snprintf(tmp, sizeof(tmp), "%s..%s", path,
                                 mg_random_str(rnd, sizeof(rnd)));
+  fs->rm(tmp);
   if (path_len < sizeof(tmp) &&
       (fd = mg_fs_open(fs, tmp, MG_FS_WRITE | MG_FS_EXCL)) != NULL) {
     result = fs->wr(fd->fd, buf, len) == len;
@@ -54,8 +56,11 @@ bool mg_file_write(struct mg_fs *fs, const char *path, const void *buf,
     if (result) {
       fs->rm(path);
       result = fs->mv(tmp, path);
+      MG_DEBUG(("mv %s -> %s result=%d", tmp, path, result));
     }
     fs->rm(tmp);
+  } else {
+    MG_ERROR(("mg_fs_open(%s) failed, path_len=%zu", tmp, path_len));
   }
   return result;
 }
diff --git a/src/fs.h b/src/fs.h
index 326e86f3..da4ff591 100644
--- a/src/fs.h
+++ b/src/fs.h
@@ -2,6 +2,7 @@
 
 #include "arch.h"
 #include "config.h"
+#include "lfs.h"
 
 // Flags returned by mg_fs.st() and passed to mg_fs.open().
 enum { MG_FS_READ = 1, MG_FS_WRITE = 2, MG_FS_DIR = 4, MG_FS_EXCL = 8 };
@@ -40,6 +41,7 @@ void mg_fs_close(struct mg_fd *fd);
 
 // Sequential directory iterator. Call repeatedly with the same buf/len;
 // each call fills buf with the next entry name. Returns false when done.
+// Note: make sure buf[0] == 0 before the first call
 bool mg_fs_ls(struct mg_fs *fs, const char *path, char *buf, size_t len);
 
 // Reads the entire file into a heap-allocated buffer. The returned mg_str is
diff --git a/src/fs_posix.c b/src/fs_posix.c
index 064dc381..8a2e58a6 100644
--- a/src/fs_posix.c
+++ b/src/fs_posix.c
@@ -10,6 +10,10 @@
 #define MG_STAT_FUNC stat
 #endif
 
+#if MG_ENABLE_LFS
+#include <dirent.h>
+#endif
+
 static int p_stat(const char *path, size_t *size, time_t *mtime) {
 #if !defined(S_ISDIR)
   MG_ERROR(("stat() API is not supported. %p %p %p", path, size, mtime));
@@ -161,7 +165,6 @@ struct dirent *readdir(DIR *d) {
 
 static void p_list(const char *dir, void (*fn)(const char *, void *),
                    void *userdata) {
-#if MG_ENABLE_DIRLIST
   struct dirent *dp;
   DIR *dirp;
   if ((dirp = (opendir(dir))) == NULL) return;
@@ -170,9 +173,6 @@ static void p_list(const char *dir, void (*fn)(const char *, void *),
     fn(dp->d_name, userdata);
   }
   closedir(dirp);
-#else
-  (void) dir, (void) fn, (void) userdata;
-#endif
 }
 
 static void *p_open(const char *path, int flags) {
diff --git a/src/lfs.c b/src/lfs.c
index e4b2c44f..28dc6d65 100644
--- a/src/lfs.c
+++ b/src/lfs.c
@@ -3,19 +3,18 @@
 
 #include "flash.h"
 #include "util.h"
+#include "lfs.h"
 
 #if MG_ENABLE_LFS
 
-#include <fcntl.h>
-#include <littlefs/lfs.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-
 #ifndef LFS_USE_RAM
 #define LFS_USE_RAM 0  // If 1, use RAM FS. If 0, use flash
 #endif
 
+#ifndef MG_LFS_SIZE
+#define MG_LFS_SIZE (64 * 1024)
+#endif
+
 #ifndef MG_LFS_BUF_SIZE
 #define MG_LFS_BUF_SIZE 64  // Buffer size used for reads, writes, and cache
 #endif
@@ -28,19 +27,6 @@
 #define MG_LFS_BLOCK_SIZE 8192
 #endif
 
-#ifndef DT_DIR
-#define DT_DIR 4
-#endif
-#ifndef DT_REG
-#define DT_REG 8
-#endif
-
-typedef struct mg_lfs_fd DIR;
-struct dirent {
-  char d_name[LFS_NAME_MAX + 1];
-  unsigned char d_type;
-};
-
 struct mg_lfs_fd {
   struct mg_lfs_fd *next;
   bool isopen;
@@ -110,29 +96,50 @@ static int lfs_driver_sync(const struct lfs_config *cfg) {
 }
 
 bool mg_lfs_init(size_t size) {
-  int result = 0;
+  //bool ok = false;
+  MG_DEBUG(("size: %zu", size));
   if (s_lfs_ready) return true;
-  if (size == 0) return false;
+  if (size == 0) {
+    MG_ERROR(("invalidsize = 0"));
+  } else {
 #if LFS_USE_RAM
-  s_cfg.block_size = MG_LFS_BLOCK_SIZE;
-  if (s_ram_fs == NULL) s_ram_fs = (uint8_t *) mg_calloc(1, size);
-  s_fs = s_ram_fs;
+    s_cfg.block_size = MG_LFS_BLOCK_SIZE;
+    if (s_ram_fs == NULL) s_ram_fs = (uint8_t *) mg_calloc(1, size);
+    s_fs = s_ram_fs;
 #else
-  if (mg_flash == NULL || mg_flash->secsz == 0 || mg_flash->size < size) return false;
-  if (mg_flash->write_fn == NULL) return false;
-  s_cfg.block_size = mg_flash->secsz;
-  s_fs = (uint8_t *) mg_flash->start + mg_flash->size - size;
+    {
+      // Some flash attributes may be initialised on ota_begin
+      int lev = mg_log_level;
+      mg_log_level = MG_LL_NONE;
+      mg_ota_begin(1);
+      mg_ota_end();
+      mg_log_set(lev);
+    }
+    if (mg_flash == NULL || mg_flash->secsz == 0 || mg_flash->size < size) {
+      MG_ERROR(("mg_flash %p secsz %zu flash_size %zu < size %zu", mg_flash, mg_flash->secsz, mg_flash->size, size));
+    } else if (mg_flash->write_fn == NULL) {
+      MG_ERROR(("flash write_fn == NULL"));
+    } else {
+      s_cfg.block_size = mg_flash->secsz;
+      s_fs = (uint8_t *) mg_flash->start + mg_flash->size - size;
+    }
 #endif
-  if (s_fs == NULL || s_cfg.block_size == 0 || size % s_cfg.block_size != 0) {
-    return false;
+    if (s_fs == NULL || s_cfg.block_size == 0 || size % s_cfg.block_size != 0) {
+      MG_ERROR(("s_fs %p blk_size %zu size %zu", s_fs, s_cfg.block_size));
+    } else {
+      s_cfg.block_count = (lfs_size_t) (size / s_cfg.block_size);
+      if (s_cfg.block_count == 0) {
+        MG_ERROR(("blk_count == 0"));
+      } else {
+        if (lfs_mount(&s_lfs, &s_cfg) != 0) lfs_format(&s_lfs, &s_cfg);
+        if (lfs_mount(&s_lfs, &s_cfg) != 0) {
+          MG_ERROR(("lfs_mount"));
+        } else {
+          s_lfs_ready = true;
+        }
+      }
+    }
   }
-  s_cfg.block_count = (lfs_size_t) (size / s_cfg.block_size);
-  if (s_cfg.block_count == 0) return false;
-  if (lfs_mount(&s_lfs, &s_cfg) != 0) {
-    lfs_format(&s_lfs, &s_cfg);
-    if (lfs_mount(&s_lfs, &s_cfg) != 0) result = -1;
-  }
-  s_lfs_ready = result == 0;
   return s_lfs_ready;
 }
 
@@ -146,6 +153,7 @@ static struct mg_lfs_fd *find_fd(int fd) {
 
 static struct mg_lfs_fd *open_fd(void) {
   struct mg_lfs_fd *f = NULL;
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   if (s_lfs_ready) {
     f = (struct mg_lfs_fd *) mg_calloc(1, sizeof(*f));
     if (f != NULL) {
@@ -173,6 +181,7 @@ int _open(const char *path, int flags, mode_t mode) {
   int err, lfs_flags = 0, fd = -1;
   struct mg_lfs_fd *f = open_fd();
   (void) mode;
+  MG_DEBUG(("%s -> %p, lfs_ready %d", path, f, s_lfs_ready));
   if (f == NULL) return -1;
   fd = f->fd;
   if ((flags & 3) == O_RDONLY) lfs_flags |= LFS_O_RDONLY;
@@ -214,11 +223,21 @@ int _lseek(int fd, int offset, int whence) {
 }
 
 int _rename(const char *oldname, const char *newname) {
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   return s_lfs_ready ? lfs_rename(&s_lfs, oldname, newname) : -1;
 }
 
-int _unlink_r(void *r, const char *a) {
-  (void) r;
+// Some libc rename() implementations have no atomic rename syscall and emulate
+// it as link() + unlink() instead of calling _rename() directly. LittleFS has
+// no real hard links, but forwarding to _rename() gives the same end result
+// (oldname becomes newname), which is all mg_file_write()'s atomic-write
+// pattern (write to a temp file, then rename it into place) needs
+int _link(const char *oldname, const char *newname) {
+  return _rename(oldname, newname);
+}
+
+int _unlink(const char *a) {
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   return s_lfs_ready ? lfs_remove(&s_lfs, a) : -1;
 }
 
@@ -227,7 +246,7 @@ DIR *opendir(const char *name) {
   if (f == NULL) return NULL;
   if (lfs_dir_open(&s_lfs, &f->dir, name) != 0) {
     close_fd(f);
-    return NULL;
+    f = NULL;
   }
   return (DIR *) f;
 }
@@ -254,7 +273,9 @@ struct dirent *readdir(DIR *dir) {
 
 int _stat(const char *path, struct stat *st) {
   struct lfs_info info;
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   if (!s_lfs_ready || lfs_stat(&s_lfs, path, &info) != 0) return -1;
+  memset(st, 0, sizeof(*st));
   st->st_mode = info.type == LFS_TYPE_DIR ? S_IFDIR : S_IFREG;
   st->st_size = info.size;
   return 0;
@@ -268,7 +289,7 @@ int _fstat(int fd, struct stat *st) {
 
 int mkdir(const char *path, mode_t mode) {
   (void) mode;
+  if (s_lfs_ready == false) mg_lfs_init(MG_LFS_SIZE);
   return s_lfs_ready ? lfs_mkdir(&s_lfs, path) : -1;
 }
-
 #endif
diff --git a/src/lfs.h b/src/lfs.h
new file mode 100644
index 00000000..6c29b3f8
--- /dev/null
+++ b/src/lfs.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#if MG_ENABLE_LFS
+#include <fcntl.h>
+#include <littlefs/lfs.h>
+
+#ifndef DT_DIR
+#define DT_DIR 4
+#endif
+#ifndef DT_REG
+#define DT_REG 8
+#endif
+
+struct dirent {
+  char d_name[LFS_NAME_MAX + 1];
+  unsigned char d_type;
+};
+
+typedef struct mg_lfs_fd  DIR;
+#endif
diff --git a/test/Makefile b/test/Makefile
index 94800a37..92d5c83f 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -106,7 +106,7 @@ mongoose.c: Makefile $(wildcard ../src/*.c) $(wildcard ../src/drivers/*.c)
 	cd .. && (export LC_ALL=C ; cat src/license.h; echo; echo '#include "mongoose.h"' ; (for F in src/*.c src/drivers/*.c ; do echo; echo '#ifdef MG_ENABLE_LINES'; echo "#line 1 \"$$F\""; echo '#endif'; cat $$F | sed -e 's,#include ".*,,'; done))> $@
 
 mongoose.h: $(HDRS) Makefile
-	cd .. && (export LC_ALL=C ; cat src/license.h; echo; echo '#ifndef MONGOOSE_H'; echo '#define MONGOOSE_H'; echo; cat src/version.h ; echo; echo '#ifdef __cplusplus'; echo 'extern "C" {'; echo '#endif'; cat src/arch.h src/arch_*.h src/os_*.h src/net_ft.h src/net_lwip.h src/net_rl.h src/config.h src/profile.h src/str.h src/queue.h src/fmt.h src/printf.h src/log.h src/timer.h src/fs.h src/util.h src/url.h src/iobuf.h src/base64.h src/md5.h src/sha1.h src/sha256.h src/event.h src/net.h src/http.h src/ssi.h src/tls.h src/tls_x25519.h src/tls_aes128.h src/tls_uecc.h src/tls_chacha20.h src/tls_rsa.h src/tls_mbed.h src/tls_openssl.h src/ws.h src/sntp.h src/mqtt.h src/dns.h src/modbus.h src/json.h src/jwt.h src/rpc.h src/dash.h src/ota.h src/health.h src/mdash.h src/flash.h src/wifi.h src/l2.h src/net_builtin.h src/bsd.h src/drivers/*.h | sed -e '/keep/! s,#include ".*,,' -e 's,^#pragma once,,'; echo; echo '#ifdef __cplusplus'; echo '}'; echo '#endif'; echo '#endif  // MONGOOSE_H')> $@
+	cd .. && (export LC_ALL=C ; cat src/license.h; echo; echo '#ifndef MONGOOSE_H'; echo '#define MONGOOSE_H'; echo; cat src/version.h ; echo; echo '#ifdef __cplusplus'; echo 'extern "C" {'; echo '#endif'; cat src/arch.h src/arch_*.h src/os_*.h src/net_ft.h src/net_lwip.h src/net_rl.h src/config.h src/profile.h src/str.h src/queue.h src/fmt.h src/printf.h src/log.h src/timer.h src/fs.h src/lfs.h src/util.h src/url.h src/iobuf.h src/base64.h src/md5.h src/sha1.h src/sha256.h src/event.h src/net.h src/http.h src/ssi.h src/tls.h src/tls_x25519.h src/tls_aes128.h src/tls_uecc.h src/tls_chacha20.h src/tls_rsa.h src/tls_mbed.h src/tls_openssl.h src/ws.h src/sntp.h src/mqtt.h src/dns.h src/modbus.h src/json.h src/jwt.h src/rpc.h src/dash.h src/ota.h src/health.h src/mdash.h src/flash.h src/wifi.h src/l2.h src/net_builtin.h src/bsd.h src/drivers/*.h | sed -e '/keep/! s,#include ".*,,' -e 's,^#pragma once,,'; echo; echo '#ifdef __cplusplus'; echo '}'; echo '#endif'; echo '#endif  // MONGOOSE_H')> $@
 
 # Check that all external (exported) symbols have "mg_" prefix
 mg_prefix: mongoose.c mongoose.h
diff --git a/tutorials/device-dashboard/full/dashboard.c b/tutorials/device-dashboard/full/dashboard.c
index fff14bca..eabbf6be 100644
--- a/tutorials/device-dashboard/full/dashboard.c
+++ b/tutorials/device-dashboard/full/dashboard.c
@@ -150,7 +150,7 @@ static bool graph1_fn(enum mg_dash_op op, struct mg_dash_user *u) {
   return true;
 }
 static struct mg_field_set set_graph1 = {"graph1", fields_graph1, graph1_fn,
-                                         NULL,     NULL};
+                                         NULL, NULL};
 
 #define NUM_POINTS_GRAPH2 100  // How many graph2 data points to send
 static char s_graph2_data[NUM_POINTS_GRAPH2 * 4 + 2 + 1];
@@ -218,6 +218,7 @@ void mg_dash_init(struct mg_mgr *mgr) {
 
 #if MG_ARCH == MG_ARCH_UNIX
   // Create demo files in the upload directory
+  mkdir("/tmp", 0755);
   mkdir("/tmp/dashboard", 0755);
   mg_file_printf(&mg_fs_posix, "/tmp/dashboard/device-config.json",
                  "{\"model\":\"example\",\"fw\":\"1.0\"}");
diff --git a/tutorials/device-dashboard/full/dashboard.html b/tutorials/device-dashboard/full/dashboard.html
index 3fb3562b..faa67da1 100644
--- a/tutorials/device-dashboard/full/dashboard.html
+++ b/tutorials/device-dashboard/full/dashboard.html
@@ -778,15 +778,22 @@ a, a:visited, a:link { text-decoration: none; }
           </div>
 
           <div class="note">
-            <p>The two default files are fake - you can delete them</p>
-            <p>However the manager works - you can upload new files. They
-              are uploaded to /tmp/ directory on the device.
-              This requires stdio (fopen/fread/...) implemeneted.</p>
-            <p>The easiest way to implement it is to use a filesystem like
-              LittleFS on your internal or external flash
-              and retarget the standard library to use it.</p>
-            <p>See <a href="https://github.com/cpq/bare-metal-programming-guide/tree/main/templates/lfs/nucleo-h563zi">this example</a> on how LittleFS can be implemented on
-              Nucleo-H563ZI internal flash partition.</p>
+            <p>This file manager uses /tmp/dashboard/ directory.
+              It works on any platform that supports
+              standard file IO: fopen, fread, fwrite, fclose.
+              This includes Linux/Mac/Windows.</p>
+            <p>
+              Mongoose provides a built-in LittleFS integration that
+              makes stadard file IO work on embedded systems like STM32.
+              For that, add "#define MG_ENABLE_LFS 1" to your
+              mongoose_config.h
+            </p>
+            <p>See
+              <a href="https://github.com/cesanta/embedded-web-file-manager">this ready-to-build example</a>
+              which implements LittleFS on Nucleo-H563ZI internal flash. You
+              can upload, delete and serve files on STM32 - which is
+              a perfect use case for confuration files, keeping and viewing logs, etc.
+            </p>
           </div>
 
         </div>
diff --git a/tutorials/stm32/nucleo-h563zi/minimal/Makefile b/tutorials/stm32/nucleo-h563zi/minimal/Makefile
index 9045ed37..8d543933 100644
--- a/tutorials/stm32/nucleo-h563zi/minimal/Makefile
+++ b/tutorials/stm32/nucleo-h563zi/minimal/Makefile
@@ -1,23 +1,26 @@
 # Copyright (c) 2026 Cesanta Software Limited
 # Environment setup: https://mongoose.ws/docs/getting-started/build-environment/
 
+MGDIR = ../../../..
+
 CFLAGS  = -W -Wall -Wextra -Wundef -Wshadow -Wdouble-promotion
 CFLAGS += -Wformat-truncation -fno-common -Wconversion -Wno-sign-conversion
 CFLAGS += -g3 -Os -ffunction-sections -fdata-sections
-CFLAGS += -I. -Icmsis_core/CMSIS/Core/Include -Icmsis_h5/Include -Imongoose
+CFLAGS += -I. -I$(MGDIR) -Icmsis_core/CMSIS/Core/Include -Icmsis_h5/Include -Imongoose
 CFLAGS += -mcpu=cortex-m33 -mthumb -mfpu=fpv5-sp-d16 -mfloat-abi=hard $(CFLAGS_EXTRA)
 LDFLAGS ?= -Tlink.ld -nostdlib -nostartfiles --specs nosys.specs -lc -lgcc -Wl,--gc-sections -Wl,-Map=$@.map
 
 SOURCES = main.c hal.c
+SOURCES += littlefs/lfs.c littlefs/lfs_util.c
 SOURCES += cmsis_h5/Source/Templates/gcc/startup_stm32h563xx.s
-SOURCES += mongoose/mongoose.c
+SOURCES += $(MGDIR)/mongoose.c
+
+# Disabled for littlefs/lfs.c
+CFLAGS += -Wno-conversion -Wno-shadow
 
 all build example: firmware.bin
 
-mongoose/mongoose.c mongoose/mongoose.h:
-	cp ../../../../mongoose.[ch] mongoose/
-
-firmware.elf: cmsis_core cmsis_h5 hal.h link.ld Makefile $(SOURCES) mongoose/mongoose.h
+firmware.elf: cmsis_core cmsis_h5 littlefs hal.h link.ld Makefile $(SOURCES) $(MGDIR)/mongoose.h
 	arm-none-eabi-gcc $(SOURCES) $(CFLAGS) $(CFLAGS_EXTRA) $(LDFLAGS) -o $@
 
 firmware.bin: firmware.elf
@@ -42,6 +45,10 @@ cmsis_core:
 cmsis_h5:
 	git clone -q -c advice.detachedHead=false --depth 1 -b v1.6.0 https://github.com/STMicroelectronics/cmsis-device-h5 $@
 
+littlefs/lfs.c littlefs/lfs_util.c: littlefs
+littlefs:
+	git clone -q -c advice.detachedHead=false --depth 1 -b v2.11.3 https://github.com/littlefs-project/littlefs $@
+
 clean:
 	rm -rf firmware.* cmsis_* mongoose/mongoose.*
 
diff --git a/tutorials/stm32/nucleo-h563zi/minimal/main.c b/tutorials/stm32/nucleo-h563zi/minimal/main.c
index cea2a7a6..b94e82a2 100644
--- a/tutorials/stm32/nucleo-h563zi/minimal/main.c
+++ b/tutorials/stm32/nucleo-h563zi/minimal/main.c
@@ -45,8 +45,20 @@ static void http_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
     struct mg_http_message *hm = (struct mg_http_message *) ev_data;
     if (mg_match(hm->uri, mg_str("/api/tick"), NULL)) {
       mg_http_reply(c, 200, "", "{%m:%llu}\n", MG_ESC("tick"), hal_get_tick());
+    } else if (mg_match(hm->uri, mg_str("/files/#"), NULL)) {
+      struct mg_http_serve_opts opts = {
+          .root_dir = "/files/=/fs/",
+          .allow_delete = true,
+          .allow_upload = true,
+      };
+      mg_http_serve_dir(c, hm, &opts);
     } else {
-      mg_http_reply(c, 200, "", "Hi from Mongoose, tick %llu\n", hal_get_tick());
+      size_t u = hal_ram_used(), t = u + hal_ram_free();
+      mg_http_reply(c, 200, "",
+                    "Hi from Mongoose!\n"
+                    "Tick %llu\n"
+                    "RAM usage: %zu / %zu (%zu %%)\n",
+                    hal_get_tick(), u, t, (size_t) (100 * u / t));
     }
   }
 }
@@ -67,6 +79,14 @@ int main(void) {
   mg_mgr_init(&mgr);
   mg_http_listen(&mgr, "http://0.0.0.0", http_ev_handler, NULL);
 
+  // Create directory for Web file manager. Will be mapped to /files/ URL
+  mkdir("/fs", 0755);
+  MG_INFO(("File manager operations:"));
+  MG_INFO(("Upload: curl IP/files/NAME --data-binary @FILE"));
+  MG_INFO(("Delete: curl IP/files/NAME -X DELETE"));
+  MG_INFO(("Show:   curl IP/files/NAME"));
+  MG_INFO(("List:   curl IP/files/"));
+
   for (;;) {
     mg_mgr_poll(&mgr, 0);
     blink_task();
diff --git a/tutorials/stm32/nucleo-h563zi/minimal/mongoose/mongoose_config.h b/tutorials/stm32/nucleo-h563zi/minimal/mongoose_config.h
similarity index 81%
rename from tutorials/stm32/nucleo-h563zi/minimal/mongoose/mongoose_config.h
rename to tutorials/stm32/nucleo-h563zi/minimal/mongoose_config.h
index cdc861c4..d1a9dff6 100644
--- a/tutorials/stm32/nucleo-h563zi/minimal/mongoose/mongoose_config.h
+++ b/tutorials/stm32/nucleo-h563zi/minimal/mongoose_config.h
@@ -12,6 +12,11 @@
 #define MG_ENABLE_PACKED_FS 1
 #define MG_ENABLE_DRIVER_STM32H 1
 
+#define MG_ENABLE_LFS 1  // Enable POSIX filesystem on interfal flash using LFS
+#define MG_LFS_SIZE (1024 * 128)  // Must be multiple of H5 8Kb sectors
+#define MG_OTA MG_OTA_STM32H5     // MG_OTA required for LFS, for flash usage
+#define MG_ENABLE_LINES 1
+
 // #define MG_DRIVER_MDC_CR 4   // RMII MDC clock divider, from 0 to 4
 // #define MG_TCPIP_PHY_ADDR 0  // PHY address
 
diff --git a/tutorials/stm32/nucleo-h563zi/minimal/sys/dirent.h b/tutorials/stm32/nucleo-h563zi/minimal/sys/dirent.h
new file mode 100644
index 00000000..e69de29b