1 /* vi: set sw=4 ts=4: */
2 /* Copyright 2005 Rob Landley <rob@landley.net>
4 * Switch from rootfs to another filesystem as the root of the mount tree.
6 * Licensed under GPL version 2, see file LICENSE in this tarball for details.
12 // Make up for header deficiencies.
14 #define RAMFS_MAGIC ((unsigned)0x858458f6)
18 #define TMPFS_MAGIC ((unsigned)0x01021994)
25 // Recursively delete contents of rootfs.
26 static void delete_contents(const char *directory, dev_t rootdev)
32 // Don't descend into other filesystems
33 if (lstat(directory, &st) || st.st_dev != rootdev)
36 // Recursively delete the contents of directories.
37 if (S_ISDIR(st.st_mode)) {
38 dir = opendir(directory);
40 while ((d = readdir(dir))) {
41 char *newdir = d->d_name;
44 if (DOT_OR_DOTDOT(newdir))
47 // Recurse to delete contents
48 newdir = concat_path_file(directory, newdir);
49 delete_contents(newdir, rootdev);
54 // Directory should now be empty. Zap it.
58 // It wasn't a directory. Zap it.
59 } else unlink(directory);
62 int switch_root_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
63 int switch_root_main(int argc UNUSED_PARAM, char **argv)
65 char *newroot, *console = NULL;
70 // Parse args (-c console)
71 opt_complementary = "-2"; // minimum 2 params
72 getopt32(argv, "+c:", &console); // '+': stop parsing at first non-option
75 // Change to new root directory and verify it's a different fs.
79 if (lstat(".", &st1) || lstat("/", &st2) || st1.st_dev == st2.st_dev) {
80 bb_error_msg_and_die("bad newroot %s", newroot);
84 // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE
85 // we mean it. (I could make this a CONFIG option, but I would get email
86 // from all the people who WILL eat their filesystems.)
87 if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs)
88 || (((unsigned)stfs.f_type != RAMFS_MAGIC) && ((unsigned)stfs.f_type != TMPFS_MAGIC))
91 bb_error_msg_and_die("not rootfs");
94 // Zap everything out of rootdev
95 delete_contents("/", rootdev);
97 // Overmount / with newdir and chroot into it. The chdir is needed to
98 // recalculate "." and ".." links.
99 if (mount(".", "/", NULL, MS_MOVE, NULL))
100 bb_perror_msg_and_die("error moving root");
104 // If a new console specified, redirect stdin/stdout/stderr to that.
107 xopen(console, O_RDWR);
112 // Exec real init. (This is why we must be pid 1.)
113 execv(argv[0], argv);
114 bb_perror_msg_and_die("bad init %s", argv[0]);