+ guestfs_error_handler_cb old_error_cb = g->error_cb;
+ g->error_cb = NULL;
+
+ const char *groups[] = { feature, NULL };
+ int r = guestfs_available (g, (char * const *) groups);
+
+ g->error_cb = old_error_cb;
+
+ return r == 0 ? 1 : 0;
+}
+
+/* Download a guest file to a local temporary file. The file is
+ * cached in the temporary directory, and is not downloaded again.
+ *
+ * The name of the temporary (downloaded) file is returned. The
+ * caller must free the pointer, but does *not* need to delete the
+ * temporary file. It will be deleted when the handle is closed.
+ *
+ * Refuse to download the guest file if it is larger than max_size.
+ * On this and other errors, NULL is returned.
+ *
+ * There is actually one cache per 'struct inspect_fs *' in order
+ * to handle the case of multiple roots.
+ */
+char *
+guestfs___download_to_tmp (guestfs_h *g, struct inspect_fs *fs,
+ const char *filename,
+ const char *basename, int64_t max_size)
+{
+ char *r;
+ int fd;
+ char devfd[32];
+ int64_t size;
+
+ /* Make the basename unique by prefixing it with the fs number. */
+ if (asprintf (&r, "%s/%ld-%s", g->tmpdir, fs - g->fses, basename) == -1) {
+ perrorf (g, "asprintf");
+ return NULL;
+ }
+
+ /* If the file has already been downloaded, return. */
+ if (access (r, R_OK) == 0)
+ return r;
+
+ /* Check size of remote file. */
+ size = guestfs_filesize (g, filename);
+ if (size == -1)
+ /* guestfs_filesize failed and has already set error in handle */
+ goto error;
+ if (size > max_size) {
+ error (g, _("size of %s is unreasonably large (%" PRIi64 " bytes)"),
+ filename, size);
+ goto error;
+ }
+
+ fd = open (r, O_WRONLY|O_CREAT|O_TRUNC|O_NOCTTY, 0600);
+ if (fd == -1) {
+ perrorf (g, "open: %s", r);
+ goto error;
+ }
+
+ snprintf (devfd, sizeof devfd, "/dev/fd/%d", fd);
+
+ if (guestfs_download (g, filename, devfd) == -1) {
+ unlink (r);
+ close (fd);
+ goto error;
+ }
+
+ if (close (fd) == -1) {
+ perrorf (g, "close: %s", r);
+ unlink (r);
+ goto error;
+ }
+
+ return r;
+
+ error:
+ free (r);
+ return NULL;
+}
+
+struct inspect_fs *
+guestfs___search_for_root (guestfs_h *g, const char *root)
+{
+ if (g->nr_fses == 0) {
+ error (g, _("no inspection data: call guestfs_inspect_os first"));