14 // Make up for header deficiencies.
17 #define RAMFS_MAGIC 0x858458f6
21 #define TMPFS_MAGIC 0x01021994
30 // Recursively delete contents of rootfs.
32 static void delete_contents(char *directory)
38 // Don't descend into other filesystems
39 if (stat(directory,&st) || st.st_dev != rootdev) return;
41 // Recursively delete the contents of directories.
42 if (S_ISDIR(st.st_mode)) {
43 if((dir = opendir(directory))) {
44 while ((d = readdir(dir))) {
45 char *newdir=d->d_name;
48 if(*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2])))
51 // Recurse to delete contents
52 newdir = alloca(strlen(directory) + strlen(d->d_name) + 2);
53 sprintf(newdir, "%s/%s", directory, d->d_name);
54 delete_contents(newdir);
58 // Directory should now be empty. Zap it.
62 // It wasn't a directory. Zap it.
64 } else unlink(directory);
67 int switch_root_main(int argc, char *argv[])
69 char *newroot, *console=NULL;
73 // Parse args (-c console)
75 bb_opt_complementally="-2";
76 bb_getopt_ulflags(argc,argv,"c:",&console);
78 // Change to new root directory and verify it's a different fs.
80 newroot=argv[optind++];
82 if (chdir(newroot) || stat(".", &st1) || stat("/", &st2) ||
83 st1.st_dev == st2.st_dev)
85 bb_error_msg_and_die("bad newroot %s",newroot);
89 // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE
90 // we mean it. (I could make this a CONFIG option, but I would get email
91 // from all the people who WILL eat their filesystemss.)
93 if (stat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) ||
94 (stfs.f_type != RAMFS_MAGIC && stfs.f_type != TMPFS_MAGIC) ||
97 bb_error_msg_and_die("not rootfs");
100 // Zap everything out of rootdev
102 delete_contents("/");
104 // Overmount / with newdir and chroot into it. The chdir is needed to
105 // recalculate "." and ".." links.
107 if (mount(".", "/", NULL, MS_MOVE, NULL) || chroot(".") || chdir("/"))
108 bb_error_msg_and_die("moving root");
110 // If a new console specified, redirect stdin/stdout/stderr to that.
114 if(open(console, O_RDWR) < 0)
115 bb_error_msg_and_die("Bad console '%s'",console);
120 // Exec real init. (This is why we must be pid 1.)
121 execv(argv[optind],argv+optind+1);
122 bb_error_msg_and_die("Bad init '%s'",argv[optind]);