commands/simple/newroot.c

   1 /*
   2 newroot.c
   3
   4 Replace the current root with a new one
   5 */
   6
   7 #include <errno.h>
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <sys/mount.h>
  12
  13 void usage(void) {
  14         fprintf(stderr, "Usage: newroot [-i] <block-special>\n");
  15         fprintf(stderr, "-i: copy mfs binary from boot image to memory\n");
  16         exit(1);
  17 }
  18
  19 int main(int argc, char *argv[])
  20 {
  21         int r;
  22         char *dev;
  23         int mountflags;
  24
  25         r = 0;
  26         mountflags = 0; /* !read-only */
  27
  28         if (argc != 2 && argc != 3) usage();
  29         if(argc == 2) {
  30                 dev = argv[1];
  31         } else if(argc == 3) {
  32                 /* -i flag was supposedly entered. Verify.*/
  33                 if(strcmp(argv[1], "-i") != 0) usage();
  34                 mountflags |= MS_REUSE;
  35                 dev = argv[2];
  36         }
  37
  38         r = mount(dev, "/", mountflags, NULL, NULL);
  39         if (r != 0) {
  40                 fprintf(stderr, "newroot: mount failed: %s\n",strerror(errno));
  41                 exit(1);
  42         }
  43
  44         return 0;
  45 }