Adding source for rootdev utility.
diff --git a/files/rootdev.c b/files/rootdev.c
new file mode 100644
index 0000000..053745d
--- /dev/null
+++ b/files/rootdev.c
@@ -0,0 +1,69 @@
+/* Taken from util-linux source. GPLv2.
+ * Emits the current rootfs device.
+ * Works by searching /dev recursively for a BLK device with the same device
+ * number as '/'.
+ */
+
+#include <stdio.h>
+#include <err.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <sys/stat.h>
+#include <string.h>
+
+
+static int
+find_dev_recursive(char *dirnamebuf, int number) {
+ DIR *dp;
+ struct dirent *dir;
+ struct stat s;
+ int dirnamelen = 0;
+
+ if ((dp = opendir(dirnamebuf)) == NULL)
+ err(1, "can't read directory %s", dirnamebuf);
+ dirnamelen = strlen(dirnamebuf);
+ while ((dir = readdir(dp)) != NULL) {
+ if (!strcmp(dir->d_name, ".") || !strcmp(dir->d_name, ".."))
+ continue;
+ if (dirnamelen + 1 + strlen(dir->d_name) > PATH_MAX)
+ continue;
+ dirnamebuf[dirnamelen] = '/';
+ strcpy(dirnamebuf+dirnamelen+1, dir->d_name);
+ if (lstat(dirnamebuf, &s) < 0)
+ continue;
+ if ((s.st_mode & S_IFMT) == S_IFBLK && s.st_rdev == number)
+ return 1;
+ if ((s.st_mode & S_IFMT) == S_IFDIR &&
+ find_dev_recursive(dirnamebuf, number))
+ return 1;
+ }
+ dirnamebuf[dirnamelen] = 0;
+ closedir(dp);
+ return 0;
+}
+
+int main(int argc, char *argv[]) {
+ struct stat s;
+ char *file = "/";
+ static char name[PATH_MAX+1];
+
+ if (argc > 1)
+ file = argv[1];
+
+ if (stat(file, &s) < 0)
+ err(1, "unable to stat %s", file);
+
+ if (!s.st_dev)
+ err(1, "unknown device number 0");
+
+ strcpy(name, "/dev");
+
+ if (!find_dev_recursive(name, s.st_dev)) {
+ fprintf(stderr, "unable to find match\n");
+ return 1;
+ }
+
+ printf("%s\n", name);
+
+ return 0;
+}