diff --git a/sys/fs/constfs/constfs.c b/sys/fs/constfs/constfs.c
index f3fcbe1c8f..3152db1b4d 100644
--- a/sys/fs/constfs/constfs.c
+++ b/sys/fs/constfs/constfs.c
@@ -33,46 +33,34 @@
 #include "debug.h"
 
 /* File system operations */
-static int constfs_mount(vfs_mount_t *mountp);
-static int constfs_umount(vfs_mount_t *mountp);
-static int constfs_unlink(vfs_mount_t *mountp, const char *name);
 static int constfs_stat(vfs_mount_t *mountp, const char *restrict name, struct stat *restrict buf);
 static int constfs_statvfs(vfs_mount_t *mountp, const char *restrict path, struct statvfs *restrict buf);
 
 /* File operations */
-static int constfs_close(vfs_file_t *filp);
 static int constfs_fstat(vfs_file_t *filp, struct stat *buf);
 static off_t constfs_lseek(vfs_file_t *filp, off_t off, int whence);
 static int constfs_open(vfs_file_t *filp, const char *name, int flags, mode_t mode, const char *abs_path);
 static ssize_t constfs_read(vfs_file_t *filp, void *dest, size_t nbytes);
-static ssize_t constfs_write(vfs_file_t *filp, const void *src, size_t nbytes);
 
 /* Directory operations */
 static int constfs_opendir(vfs_DIR *dirp, const char *dirname, const char *abs_path);
 static int constfs_readdir(vfs_DIR *dirp, vfs_dirent_t *entry);
-static int constfs_closedir(vfs_DIR *dirp);
 
 static const vfs_file_system_ops_t constfs_fs_ops = {
-    .mount = constfs_mount,
-    .umount = constfs_umount,
-    .unlink = constfs_unlink,
     .statvfs = constfs_statvfs,
     .stat = constfs_stat,
 };
 
 static const vfs_file_ops_t constfs_file_ops = {
-    .close = constfs_close,
     .fstat = constfs_fstat,
     .lseek = constfs_lseek,
     .open  = constfs_open,
     .read  = constfs_read,
-    .write = constfs_write,
 };
 
 static const vfs_dir_ops_t constfs_dir_ops = {
     .opendir = constfs_opendir,
     .readdir = constfs_readdir,
-    .closedir = constfs_closedir,
 };
 
 const vfs_file_system_t constfs_file_system = {
@@ -91,28 +79,6 @@ const vfs_file_system_t constfs_file_system = {
  */
 static void _constfs_write_stat(const constfs_file_t *fp, struct stat *restrict buf);
 
-static int constfs_mount(vfs_mount_t *mountp)
-{
-    /* perform any extra initialization here */
-    (void) mountp; /* prevent warning: unused parameter */
-    return 0;
-}
-
-static int constfs_umount(vfs_mount_t *mountp)
-{
-    /* free resources and perform any clean up here */
-    (void) mountp; /* prevent warning: unused parameter */
-    return 0;
-}
-
-static int constfs_unlink(vfs_mount_t *mountp, const char *name)
-{
-    /* Removing files is prohibited */
-    (void) mountp; /* prevent warning: unused parameter */
-    (void) name; /* prevent warning: unused parameter */
-    return -EROFS;
-}
-
 static int constfs_stat(vfs_mount_t *mountp, const char *restrict name, struct stat *restrict buf)
 {
     (void) name;
@@ -162,13 +128,6 @@ static int constfs_statvfs(vfs_mount_t *mountp, const char *restrict path, struc
     return 0;
 }
 
-static int constfs_close(vfs_file_t *filp)
-{
-    /* perform any necessary clean ups */
-    (void) filp; /* prevent warning: unused parameter */
-    return 0;
-}
-
 static int constfs_fstat(vfs_file_t *filp, struct stat *buf)
 {
     constfs_file_t *fp = filp->private_data.ptr;
@@ -244,18 +203,6 @@ static ssize_t constfs_read(vfs_file_t *filp, void *dest, size_t nbytes)
     return nbytes;
 }
 
-static ssize_t constfs_write(vfs_file_t *filp, const void *src, size_t nbytes)
-{
-    DEBUG("constfs_write: %p, %p, %lu\n", (void *)filp, src, (unsigned long)nbytes);
-    /* Read only file system */
-    DEBUG("constfs_write: read only FS\n");
-    /* prevent warning: unused parameter */
-    (void) filp;
-    (void) src;
-    (void) nbytes;
-    return -EBADF;
-}
-
 static int constfs_opendir(vfs_DIR *dirp, const char *dirname, const char *abs_path)
 {
     (void) abs_path;
@@ -298,14 +245,6 @@ static int constfs_readdir(vfs_DIR *dirp, vfs_dirent_t *entry)
     return 1;
 }
 
-static int constfs_closedir(vfs_DIR *dirp)
-{
-    /* Just an example, it's not necessary to define closedir if there is
-     * nothing to clean up */
-    (void) dirp;
-    return 0;
-}
-
 static void _constfs_write_stat(const constfs_file_t *fp, struct stat *restrict buf)
 {
     /* buffer is cleared by vfs already */
diff --git a/sys/vfs/vfs.c b/sys/vfs/vfs.c
index 90fbbf9aef..6a9a7f549e 100644
--- a/sys/vfs/vfs.c
+++ b/sys/vfs/vfs.c
@@ -609,7 +609,7 @@ int vfs_rename(const char *from_path, const char *to_path)
         DEBUG("vfs_rename: rename not supported by fs!\n");
         /* remember to decrement the open_files count */
         atomic_fetch_sub(&mountp->open_files, 1);
-        return -EPERM;
+        return -EROFS;
     }
     const char *rel_to;
     vfs_mount_t *mountp_to;
@@ -668,7 +668,7 @@ int vfs_unlink(const char *name)
         DEBUG("vfs_unlink: unlink not supported by fs!\n");
         /* remember to decrement the open_files count */
         atomic_fetch_sub(&mountp->open_files, 1);
-        return -EPERM;
+        return -EROFS;
     }
     res = mountp->fs->fs_op->unlink(mountp, rel_path);
     DEBUG("vfs_unlink: unlink %p, \"%s\"", (void *)mountp, rel_path);
@@ -705,7 +705,7 @@ int vfs_mkdir(const char *name, mode_t mode)
         DEBUG("vfs_mkdir: mkdir not supported by fs!\n");
         /* remember to decrement the open_files count */
         atomic_fetch_sub(&mountp->open_files, 1);
-        return -EPERM;
+        return -EROFS;
     }
     res = mountp->fs->fs_op->mkdir(mountp, rel_path, mode);
     DEBUG("vfs_mkdir: mkdir %p, \"%s\"", (void *)mountp, rel_path);
@@ -742,7 +742,7 @@ int vfs_rmdir(const char *name)
         DEBUG("vfs_rmdir: rmdir not supported by fs!\n");
         /* remember to decrement the open_files count */
         atomic_fetch_sub(&mountp->open_files, 1);
-        return -EPERM;
+        return -EROFS;
     }
     res = mountp->fs->fs_op->rmdir(mountp, rel_path);
     DEBUG("vfs_rmdir: rmdir %p, \"%s\"", (void *)mountp, rel_path);
diff --git a/tests/unittests/tests-vfs/tests-vfs-file-system-ops.c b/tests/unittests/tests-vfs/tests-vfs-file-system-ops.c
index 91da825557..05070109a4 100644
--- a/tests/unittests/tests-vfs/tests-vfs-file-system-ops.c
+++ b/tests/unittests/tests-vfs/tests-vfs-file-system-ops.c
@@ -96,28 +96,28 @@ static void test_vfs_null_fs_ops_rename(void)
 {
     TEST_ASSERT_EQUAL_INT(0, _test_vfs_fs_op_mount_res);
     int res = vfs_rename("/test/foo", "/test/bar");
-    TEST_ASSERT_EQUAL_INT(-EPERM, res);
+    TEST_ASSERT_EQUAL_INT(-EROFS, res);
 }
 
 static void test_vfs_null_fs_ops_unlink(void)
 {
     TEST_ASSERT_EQUAL_INT(0, _test_vfs_fs_op_mount_res);
     int res = vfs_unlink("/test/foo");
-    TEST_ASSERT_EQUAL_INT(-EPERM, res);
+    TEST_ASSERT_EQUAL_INT(-EROFS, res);
 }
 
 static void test_vfs_null_fs_ops_mkdir(void)
 {
     TEST_ASSERT_EQUAL_INT(0, _test_vfs_fs_op_mount_res);
     int res = vfs_mkdir("/test/foodir", 0);
-    TEST_ASSERT_EQUAL_INT(-EPERM, res);
+    TEST_ASSERT_EQUAL_INT(-EROFS, res);
 }
 
 static void test_vfs_null_fs_ops_rmdir(void)
 {
     TEST_ASSERT_EQUAL_INT(0, _test_vfs_fs_op_mount_res);
     int res = vfs_rmdir("/test/foodir");
-    TEST_ASSERT_EQUAL_INT(-EPERM, res);
+    TEST_ASSERT_EQUAL_INT(-EROFS, res);
 }
 
 static void test_vfs_null_fs_ops_stat(void)