diff --git a/src/trace.c b/src/trace.c
index 240a17f..bb4d696 100644
--- a/src/trace.c
+++ b/src/trace.c
@@ -31,6 +31,7 @@
 #include <sys/types.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
+#include <sys/param.h>
 
 #include <errno.h>
 #include <fcntl.h>
@@ -88,6 +89,7 @@
 /* Prototypes for static functions */
 static int       read_trace        (const void *parent,
 				    int dfd, const char *path,
+				    const PathPrefixOption *path_prefix,
 				    PackFile **files, size_t *num_files);
 static void      fix_path          (char *pathname);
 static int       trace_add_path    (const void *parent, const char *pathname,
@@ -114,7 +116,9 @@ sig_interrupt (int signum)
 
 int
 trace (int daemonise,
-       int timeout)
+       int timeout,
+       const char *filename_to_replace,
+       const PathPrefixOption *path_prefix)
 {
 	int                 dfd;
 	FILE                *fp;
@@ -248,7 +252,7 @@ trace (int daemonise,
 		;
 
 	/* Read trace log */
-	if (read_trace (NULL, dfd, "trace", &files, &num_files) < 0)
+	if (read_trace (NULL, dfd, "trace", path_prefix, &files, &num_files) < 0)
 		goto error;
 
 	/*
@@ -284,6 +288,15 @@ trace (int daemonise,
 			continue;
 		}
 
+		/* If filename_to_replace is not NULL, only write out the
+		 * file and skip others.
+		 */
+		if (filename_to_replace &&
+		    strcmp (filename_to_replace, filename)) {
+			nih_info ("Skipping %s", filename);
+			continue;
+		}
+
 		nih_info ("Writing %s", filename);
 
 		/* We only need to apply additional sorting to the
@@ -320,6 +333,7 @@ static int
 read_trace (const void *parent,
 	    int         dfd,
 	    const char *path,
+	    const PathPrefixOption *path_prefix,
 	    PackFile ** files,
 	    size_t *    num_files)
 {
@@ -328,6 +342,7 @@ read_trace (const void *parent,
 	char *line;
 
 	nih_assert (path != NULL);
+	nih_assert (path_prefix != NULL);
 	nih_assert (files != NULL);
 	nih_assert (num_files != NULL);
 
@@ -373,9 +388,22 @@ read_trace (const void *parent,
 		*end = '\0';
 
 		fix_path (ptr);
+		if (path_prefix->st_dev != NODEV && ptr[0] == '/') {
+			struct stat stbuf;
+			char *rewritten = nih_sprintf (
+			    line, "%s%s", path_prefix->prefix, ptr);
+			if (! lstat (rewritten, &stbuf) &&
+			    stbuf.st_dev == path_prefix->st_dev) {
+				/* If |rewritten| exists on the same device as
+				 * path_prefix->st_dev, record the rewritten one
+				 * instead of the original path.
+				 */
+				ptr = rewritten;
+			}
+		}
 		trace_add_path (parent, ptr, files, num_files);
 
-		nih_free (line);
+		nih_free (line);  /* also frees |rewritten| */
 	}
 
 	if (fclose (fp) < 0)
diff --git a/src/trace.h b/src/trace.h
index 8e10890..986b10c 100644
--- a/src/trace.h
+++ b/src/trace.h
@@ -19,6 +19,7 @@
 #ifndef UREADAHEAD_TRACE_H
 #define UREADAHEAD_TRACE_H
 
+#include <limits.h>
 #include <sys/types.h>
 
 #include <nih/macros.h>
@@ -27,7 +28,14 @@
 
 NIH_BEGIN_EXTERN
 
-int trace (int daemonise, int timeout);
+typedef struct path_prefix_option {
+        dev_t st_dev;
+        char prefix[PATH_MAX];
+} PathPrefixOption;
+
+int trace (int daemonise, int timeout,
+           const char *filename_to_replace,
+           const PathPrefixOption *path_prefix);
 
 NIH_END_EXTERN
 
diff --git a/src/ureadahead.c b/src/ureadahead.c
index 0cd4994..0e91693 100644
--- a/src/ureadahead.c
+++ b/src/ureadahead.c
@@ -30,6 +30,7 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/param.h>
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -86,6 +87,47 @@ static int dump_pack = FALSE;
  **/
 static SortOption sort_pack = SORT_OPEN;
 
+/**
+ * path_prefix:
+ *
+ * path_prefix.st_dev is set to >=0 if we should prepend path_prefix.prefix
+ * to all path names on the device.
+ **/
+static PathPrefixOption path_prefix = { NODEV };
+
+static int
+path_prefix_option (NihOption  *option,
+                    const char *arg)
+{
+	PathPrefixOption *value;
+	struct stat st;
+	dev_t st_dev;
+
+	nih_assert (option != NULL);
+	nih_assert (option->value != NULL);
+	nih_assert (arg != NULL);
+
+	value = (PathPrefixOption *)option->value;
+
+	if (strlen (arg) >= PATH_MAX) {
+		goto error;
+	}
+
+	if (lstat (arg, &st) < 0 || !S_ISDIR (st.st_mode)) {
+		goto error;
+	}
+
+	value->st_dev = st.st_dev;
+	strcpy (value->prefix, arg);
+
+	return 0;
+
+error:
+	fprintf (stderr, _("%s: illegal argument: %s\n"),
+		 program_name, arg);
+	nih_main_suggest_help ();
+	return -1;
+}
 
 static int
 sort_option (NihOption  *option,
@@ -134,6 +176,8 @@ static NihOption options[] = {
 	  NULL, NULL, &dump_pack, NULL },
 	{ 0, "sort", N_("how to sort the pack file when dumping [default: path]"),
 	  NULL, "SORT", &sort_pack, sort_option },
+	{ 0, "path-prefix", N_("pathname to prepend for files on the device"),
+	  NULL, "PREFIX", &path_prefix, path_prefix_option },
 
 	NIH_OPTION_LAST
 };
@@ -165,13 +209,14 @@ main (int   argc,
 	if (! args)
 		exit (1);
 
+	/* Lookup the filename for the pack based on the path given
+	 * (if any).
+	 */
+	filename = pack_file_name (NULL, args[0]);
+
 	if (! force_trace) {
 		NihError *err;
 
-		/* Lookup the filename for the pack based on the path given
-		 * (if any).
-		 */
-		filename = pack_file_name (NULL, args[0]);
 		if (! filename) {
 			NihError *err;
 
@@ -220,7 +265,7 @@ main (int   argc,
 	}
 
 	/* Trace to generate new pack files */
-	if (trace (daemonise, timeout) < 0) {
+	if (trace (daemonise, timeout, filename, &path_prefix) < 0) {
 		NihError *err;
 
 		err = nih_error_get ();