diff --git a/sc2/src/sc2code/libs/uio/debug.c b/sc2/src/sc2code/libs/uio/debug.c
index e416968fd..6b1d170ae 100644
--- a/sc2/src/sc2code/libs/uio/debug.c
+++ b/sc2/src/sc2code/libs/uio/debug.c
@@ -63,6 +63,7 @@ static int debugCmdLs(DebugContext *debugContext, int argc, char *argv[]);
 static int debugCmdMem(DebugContext *debugContext, int argc, char *argv[]);
 static int debugCmdMkDir(DebugContext *debugContext, int argc, char *argv[]);
 static int debugCmdMount(DebugContext *debugContext, int argc, char *argv[]);
+static int debugCmdMv(DebugContext *debugContext, int argc, char *argv[]);
 static int debugCmdPwd(DebugContext *debugContext, int argc, char *argv[]);
 static int debugCmdRm(DebugContext *debugContext, int argc, char *argv[]);
 static int debugCmdRmDir(DebugContext *debugContext, int argc, char *argv[]);
@@ -92,6 +93,7 @@ DebugCommand debugCommands[] = {
 	{ "mem", debugCmdMem },
 	{ "mkdir", debugCmdMkDir },
 	{ "mount", debugCmdMount },
+	{ "mv", debugCmdMv },
 	{ "pwd", debugCmdPwd },
 	{ "rm", debugCmdRm },
 	{ "rmdir", debugCmdRmDir },
@@ -634,6 +636,24 @@ debugCmdMount(DebugContext *debugContext, int argc, char *argv[]) {
 	return 0;
 }
 
+static int
+debugCmdMv(DebugContext *debugContext, int argc, char *argv[]) {
+	int retVal;
+	
+	if (argc != 3) {
+		fprintf(debugContext->err, "Invalid number of arguments.\n");
+		return 1;
+	}
+	
+	retVal = uio_rename(debugContext->cwd, argv[1],
+			debugContext->cwd, argv[2]);
+	if (retVal == -1) {
+		fprintf(debugContext->err, "Could not rename: %s\n", strerror(errno));
+		return 1;
+	}
+	return 0;
+}
+
 static int
 debugCmdPwd(DebugContext *debugContext, int argc, char *argv[]) {
 	uio_DirHandle_print(debugContext->cwd, debugContext->out);
diff --git a/sc2/src/sc2code/libs/uio/doc/todo b/sc2/src/sc2code/libs/uio/doc/todo
index d3c3de46e..dae859a1c 100644
--- a/sc2/src/sc2code/libs/uio/doc/todo
+++ b/sc2/src/sc2code/libs/uio/doc/todo
@@ -35,6 +35,9 @@ Bugs:
 - uio_Stream file might get unaligned (not sure).
 - 'openDir(repository, "dir/")' will have the trailing '/'
   in the dirHandle, which will cause problems.
+- uio_rename() doesn't work on directories
+  uio_GetPhysicalAccess() needs to be changed so that it works the same on
+  dirs as on files. stat() can be cleaned up too then.
 
 Extra features (not necessary for UQM):
 - Make functions to use for uio_malloc, uio_free and uio_realloc
@@ -56,6 +59,11 @@ Extra features (not necessary for UQM):
   is accessed with the long vs the short ("PROGRA~1") name, or when
   capitalisation is involved.
 - accept non-dir, non-regular-file dir entries in stdio.
+- Add non-merging mounts. Make 'merging' an option for the mount.
+- make uio_rename() work cross-fs, or provide a wrapper which does that.
+  (the system rename() doesn't work cross-fs either, so keeping uio_rename()
+  as it is makes sense, as I'm trying to stay close to the system functions,
+  even though hiding file systems from the user would be nicer)
 
 Optimisations (not necessary for UQM):
 - use mmap for fileBlocks
diff --git a/sc2/src/sc2code/libs/uio/fstypes.h b/sc2/src/sc2code/libs/uio/fstypes.h
index 8a7416e54..27986d6fe 100644
--- a/sc2/src/sc2code/libs/uio/fstypes.h
+++ b/sc2/src/sc2code/libs/uio/fstypes.h
@@ -65,10 +65,12 @@ struct uio_FileSystemHandler {
 	int               (*fstat)    (uio_Handle *, struct stat *);
 	int               (*stat)     (uio_PDirHandle *, const char *,
 			struct stat *);
-	uio_PDirHandle *   (*mkdir)    (uio_PDirHandle *, const char *, mode_t);
-	uio_Handle *       (*open)     (uio_PDirHandle *, const char *, int,
+	uio_PDirHandle *  (*mkdir)    (uio_PDirHandle *, const char *, mode_t);
+	uio_Handle *      (*open)     (uio_PDirHandle *, const char *, int,
 			mode_t);
 	ssize_t           (*read)     (uio_Handle *, void *, size_t);
+	int               (*rename)   (uio_PDirHandle *, const char *,
+			uio_PDirHandle *, const char *);
 	int               (*rmdir)    (uio_PDirHandle *, const char *);
 	off_t             (*seek)     (uio_Handle *, off_t, int);
 	ssize_t           (*write)    (uio_Handle *, const void *, size_t);
diff --git a/sc2/src/sc2code/libs/uio/io.c b/sc2/src/sc2code/libs/uio/io.c
index f895fe436..c5c8fb5af 100644
--- a/sc2/src/sc2code/libs/uio/io.c
+++ b/sc2/src/sc2code/libs/uio/io.c
@@ -329,6 +329,81 @@ uio_close(uio_Handle *handle) {
 	return 0;
 }
 
+int
+uio_rename(uio_DirHandle *oldDir, const char *oldPath,
+		uio_DirHandle *newDir, const char *newPath) {
+	uio_PDirHandle *oldPReadDir, *newPReadDir, *newPWriteDir;
+	uio_MountInfo *oldReadMountInfo, *newReadMountInfo, *newWriteMountInfo;
+	char *oldName, *newName;
+	int retVal;
+
+	if (uio_getPhysicalAccess(oldDir, oldPath, O_RDONLY, 0,
+			&oldReadMountInfo, &oldPReadDir,
+			NULL, NULL, &oldName) == -1) {
+		// errno is set
+		return -1;
+	}
+
+	if (uio_getPhysicalAccess(newDir, newPath, O_WRONLY | O_CREAT | O_EXCL,
+			uio_GPA_NOWRITE, &newReadMountInfo, &newPReadDir,
+			&newWriteMountInfo, &newPWriteDir, &newName) == -1) {
+		int saveErrno = errno;
+		uio_PDirHandle_unref(oldPReadDir);
+		uio_free(oldName);
+		errno = saveErrno;
+		return -1;
+	}
+
+	if (oldReadMountInfo != newWriteMountInfo) {
+		uio_PDirHandle_unref(oldPReadDir);
+		uio_PDirHandle_unref(newPReadDir);
+		uio_PDirHandle_unref(newPWriteDir);
+		uio_free(oldName);
+		uio_free(newName);
+		errno = EXDEV;
+		return -1;
+	}
+
+	if (uio_mountInfoIsReadOnly(oldReadMountInfo)) {
+		uio_PDirHandle_unref(oldPReadDir);
+		uio_PDirHandle_unref(newPReadDir);
+		uio_PDirHandle_unref(newPWriteDir);
+		uio_free(oldName);
+		uio_free(newName);
+		errno = EROFS;
+		return -1;
+	}
+	
+	if (oldReadMountInfo->pDirHandle->pRoot->handler->rename == NULL) {
+		uio_PDirHandle_unref(oldPReadDir);
+		uio_PDirHandle_unref(newPReadDir);
+		uio_PDirHandle_unref(newPWriteDir);
+		uio_free(oldName);
+		uio_free(newName);
+		errno = ENOSYS;
+		return -1;
+	}
+	retVal = oldReadMountInfo->pDirHandle->pRoot->handler->rename(
+			oldPReadDir, oldName, newPReadDir, newName);
+	if (retVal == -1) {
+		int saveErrno = errno;
+		uio_PDirHandle_unref(oldPReadDir);
+		uio_PDirHandle_unref(newPReadDir);
+		uio_PDirHandle_unref(newPWriteDir);
+		uio_free(oldName);
+		uio_free(newName);
+		errno = saveErrno;
+		return -1;
+	}
+
+	uio_PDirHandle_unref(oldPReadDir);
+	uio_PDirHandle_unref(newPReadDir);
+	uio_PDirHandle_unref(newPWriteDir);
+	uio_free(oldName);
+	uio_free(newName);
+	return 0;
+}
+
 int
 uio_fstat(uio_Handle *handle, struct stat *statBuf) {
 	if (handle->root->handler->fstat == NULL) {
@@ -345,7 +420,7 @@ uio_stat(uio_DirHandle *dir, const char *path, struct stat *statBuf) {
 	char *name;
 	int result;
 
-	if (uio_getPhysicalAccess(dir, path, O_RDONLY,
+	if (uio_getPhysicalAccess(dir, path, O_RDONLY, 0,
 			&readMountInfo, &pReadDir,
 			NULL, NULL, &name) == -1) {
 		if (uio_statDir(dir, path, statBuf) == -1) {
@@ -435,7 +510,7 @@ uio_mkdir(uio_DirHandle *dir, const char *path, mode_t mode) {
 	char *name;
 	uio_PDirHandle *newDirHandle;
 
-	if (uio_getPhysicalAccess(dir, path, O_WRONLY | O_CREAT | O_EXCL,
+	if (uio_getPhysicalAccess(dir, path, O_WRONLY | O_CREAT | O_EXCL, 0,
 			&readMountInfo, &pReadDir,
 			&writeMountInfo, &pWriteDir, &name) == -1) {
 		// errno is set
@@ -474,7 +549,7 @@ uio_open(uio_DirHandle *dir, const char *path, int flags, mode_t mode) {
 	char *name;
 	uio_Handle *handle;
 	
-	if (uio_getPhysicalAccess(dir, path, flags,
+	if (uio_getPhysicalAccess(dir, path, flags, 0,
 			&readMountInfo, &readPDirHandle,
 			&writeMountInfo, &writePDirHandle, &name) == -1) {
 		// errno is set
diff --git a/sc2/src/sc2code/libs/uio/io.h b/sc2/src/sc2code/libs/uio/io.h
index 036b8c0af..6ab56dafe 100644
--- a/sc2/src/sc2code/libs/uio/io.h
+++ b/sc2/src/sc2code/libs/uio/io.h
@@ -94,6 +94,10 @@ uio_Handle *uio_open(uio_DirHandle *dir, const char *file, int flags,
 // Close a file descriptor for a file opened by uio_open
 int uio_close(uio_Handle *handle);
 
+// Rename or move a file or directory.
+int uio_rename(uio_DirHandle *oldDir, const char *oldPath,
+		uio_DirHandle *newDir, const char *newPath);
+
 // Fstat a file descriptor
 int uio_fstat(uio_Handle *handle, struct stat *statBuf);
 
diff --git a/sc2/src/sc2code/libs/uio/ioaux.c b/sc2/src/sc2code/libs/uio/ioaux.c
index e5d9ce0f8..deebdc8a3 100644
--- a/sc2/src/sc2code/libs/uio/ioaux.c
+++ b/sc2/src/sc2code/libs/uio/ioaux.c
@@ -257,6 +257,12 @@ copyError(int error,
  *              		Either O_RDONLY, O_RDWR, O_WRONLY. They may be
  *              		OR'd with other values accepted by open(). These
  *              		are ignored.
+ *              extraFlags - either 0 or uio_GPA_NOWRITE
+ *              		When 0, the path will be created if it doesn't
+ *              		exist in the writing location, but does exist
+ *                      in the reading location. With uio_GPA_NOWRITE, it
+ *                      won't be created, and -1 will be returned and errno
+ *                      will be set to ENOENT.
  *              mountInfoReadPtr - pointer to location where the pointer
  *              		to the MountInfo structure for the reading location
  *              		should be stored.
@@ -272,8 +278,8 @@ copyError(int error,
  *                      to by readPDirHandlePtr, the handles will be the
  *                      same too.
  *              restPtr - pointer to a newly created string with as contents
- *                        the last component of 'path'.
- *                        The caller is responsible for freeing this.
+ *              		the last component of 'path'.
+ *              		The caller is responsible for freeing this.
  * Returns:     0 - success
  *              -1 - failure (errno set)
  * NB:          This is the function that would most benefit from
@@ -283,7 +289,7 @@ copyError(int error,
  */
 int
 uio_getPhysicalAccess(uio_DirHandle *dirHandle, const char *path,
-		int flags,
+		int flags, int extraFlags,
 		uio_MountInfo **mountInfoReadPtr, uio_PDirHandle **readPDirHandlePtr,
 		uio_MountInfo **mountInfoWritePtr, uio_PDirHandle **writePDirHandlePtr,
 		char **restPtr) {
@@ -433,6 +439,15 @@ uio_getPhysicalAccess(uio_DirHandle *dirHandle, const char *path,
 
 	// There exists no path for a write dir, so it will have to be created.
 	// writeMountInfo indicates the physical tree where it should end up.
+
+	if (extraFlags & uio_GPA_NOWRITE) {
+		// The caller has specified that the path should not be created.
+		uio_PDirHandle_unref(readPDirHandle);
+		uio_free(fullPath);
+		errno = ENOENT;
+		return -1;
+	}
+	
 	pRootPath = uio_mountTreeItemRestPath(writeItem, tree->lastComp,
 			fullPath);
 
diff --git a/sc2/src/sc2code/libs/uio/ioaux.h b/sc2/src/sc2code/libs/uio/ioaux.h
index 68093631a..5a2e7e3a1 100644
--- a/sc2/src/sc2code/libs/uio/ioaux.h
+++ b/sc2/src/sc2code/libs/uio/ioaux.h
@@ -33,9 +33,10 @@ uio_PDirHandle *uio_makePath(uio_PDirHandle *pDirHandle, const char *path,
 int uio_copyFilePhysical(uio_PDirHandle *fromDir, const char *fromName,
 		uio_PDirHandle *toDir, const char *toName);
 int uio_getPhysicalAccess(uio_DirHandle *dirHandle, const char *path,
-		int flags, uio_MountInfo **mountInfoReadPtr,
+		int flags, int extraFlags, uio_MountInfo **mountInfoReadPtr,
 		uio_PDirHandle **readPDirHandlePtr, uio_MountInfo **mountInfoWritePtr,
 		uio_PDirHandle **writePDirHandlePtr, char **restPtr);
+#define uio_GPA_NOWRITE 1
 int uio_getPathPhysicalDirs(uio_DirHandle *dirHandle, const char *path,
 		size_t pathLen, uio_PDirHandle ***resPDirHandles,
 		int *resNumPDirHandles, uio_MountTreeItem ***resItems);
diff --git a/sc2/src/sc2code/libs/uio/stdio/stdio.c b/sc2/src/sc2code/libs/uio/stdio/stdio.c
index dbc0d0a9b..cc85e47f3 100644
--- a/sc2/src/sc2code/libs/uio/stdio/stdio.c
+++ b/sc2/src/sc2code/libs/uio/stdio/stdio.c
@@ -18,6 +18,9 @@
  *
  */
 
+// The GPDir structures and functions are used for caching only.
+
+
 #include "./stdio.h"
 
 #ifdef WIN32
@@ -71,6 +74,7 @@ uio_FileSystemHandler stdio_fileSystemHandler = {
 	/* .mkdir  = */  stdio_mkdir,
 	/* .open   = */  stdio_open,
 	/* .read   = */  stdio_read,
+	/* .rename = */  stdio_rename,
 	/* .rmdir  = */  stdio_rmdir,
 	/* .seek   = */  stdio_seek,
 	/* .write  = */  stdio_write,
@@ -201,10 +205,12 @@ stdio_open(uio_PDirHandle *pDirHandle, const char *file, int flags,
 	}
 	uio_free(path);
 
+#if 0
 	if (flags & O_CREAT) {
 		if (uio_GPDir_getGPDirEntry(pDirHandle->extra, file) == NULL)
 			stdio_addFile(pDirHandle->extra, file);
 	}
+#endif
 
 	handle = uio_malloc(sizeof (stdio_Handle));
 	handle->fd = fd;
@@ -217,6 +223,53 @@ stdio_read(uio_Handle *handle, void *buf, size_t count) {
 	return read(handle->native->fd, buf, count);
 }
 
+int
+stdio_rename(uio_PDirHandle *oldPDirHandle, const char *oldName,
+		uio_PDirHandle *newPDirHandle, const char *newName) {
+	char *newPath, *oldPath;
+	int result;
+
+	oldPath = joinPaths(stdio_getPath(oldPDirHandle->extra), oldName);
+	if (oldPath == NULL) {
+		// errno is set
+		return -1;
+	}
+	
+	newPath = joinPaths(stdio_getPath(newPDirHandle->extra), newName);
+	if (newPath == NULL) {
+		// errno is set
+		uio_free(oldPath);
+		return -1;
+	}
+	
+	result = rename(oldPath, newPath);
+	if (result == -1) {
+		int saveErrno = errno;
+		uio_free(oldPath);
+		uio_free(newPath);
+		errno = saveErrno;
+		return -1;
+	}
+
+	uio_free(oldPath);
+	uio_free(newPath);
+
+	{
+		// update the GPDir structure
+		uio_GPDirEntry *entry;
+
+		// TODO: add locking
+		entry = uio_GPDir_getGPDirEntry(oldPDirHandle->extra, oldName);
+		if (entry != NULL) {
+			uio_GPDirEntries_remove(oldPDirHandle->extra->entries, oldName);
+			uio_GPDirEntries_add(newPDirHandle->extra->entries, newName,
+					entry);
+		}
+	}
+		
+	return result;
+}
+
 int
 stdio_rmdir(uio_PDirHandle *pDirHandle, const char *name) {
 	char *path;
diff --git a/sc2/src/sc2code/libs/uio/stdio/stdio.h b/sc2/src/sc2code/libs/uio/stdio/stdio.h
index a1145fd29..a5a16735b 100644
--- a/sc2/src/sc2code/libs/uio/stdio/stdio.h
+++ b/sc2/src/sc2code/libs/uio/stdio/stdio.h
@@ -87,6 +87,8 @@ int stdio_fstat(uio_Handle *handle, struct stat *statBuf);
 int stdio_stat(uio_PDirHandle *pDirHandle, const char *name,
 		struct stat *statBuf);
 ssize_t stdio_read(uio_Handle *handle, void *buf, size_t count);
+int stdio_rename(uio_PDirHandle *oldPDirHandle, const char *oldName,
+		uio_PDirHandle *newPDirHandle, const char *newName);
 int stdio_rmdir(uio_PDirHandle *pDirHandle, const char *name);
 off_t stdio_seek(uio_Handle *handle, off_t offset, int whence);
 ssize_t stdio_write(uio_Handle *handle, const void *buf, size_t count);
diff --git a/sc2/src/sc2code/libs/uio/zip/zip.c b/sc2/src/sc2code/libs/uio/zip/zip.c
index fa975c08a..6c273a1b7 100644
--- a/sc2/src/sc2code/libs/uio/zip/zip.c
+++ b/sc2/src/sc2code/libs/uio/zip/zip.c
@@ -102,6 +102,7 @@ uio_FileSystemHandler zip_fileSystemHandler = {
 	/* .mkdir  = */  NULL,
 	/* .open   = */  zip_open,
 	/* .read   = */  zip_read,
+	/* .rename = */  NULL,
 	/* .rmdir  = */  NULL,
 	/* .seek   = */  zip_seek,
 	/* .write  = */  NULL,