// Recursively delete contents of rootfs. static void delete_contents(const char *directory, dev_t rootdev) { DIR *dir; struct dirent *d; struct stat st; // Don't descend into other filesystems if (lstat(directory, &st) || st.st_dev != rootdev) return; // Recursively delete the contents of directories. if (S_ISDIR(st.st_mode)) { dir = opendir(directory); if (dir) { while ((d = readdir(dir))) { char *newdir = d->d_name; // Skip . and .. if (DOT_OR_DOTDOT(newdir)) continue; // Recurse to delete contents newdir = concat_path_file(directory, newdir); delete_contents(newdir, rootdev); free(newdir); } closedir(dir); // Directory should now be empty. Zap it. rmdir(directory); } // It wasn't a directory. Zap it. } else unlink(directory); }
static void delete_contents(const char *directory) { DIR *dir; struct dirent *d; struct stat st; // Don't descend into other filesystems if (lstat(directory, &st) || st.st_dev != rootdev) return; // Recursively delete the contents of directories. if (S_ISDIR(st.st_mode)) { dir = opendir(directory); if (dir) { while ((d = readdir(dir))) { char *newdir = d->d_name; // Skip . and .. if (*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2]))) continue; // Recurse to delete contents newdir = alloca(strlen(directory) + strlen(d->d_name) + 2); sprintf(newdir, "%s/%s", directory, d->d_name); delete_contents(newdir); } closedir(dir); // Directory should now be empty. Zap it. rmdir(directory); } // It wasn't a directory. Zap it. } else unlink(directory); }
int switch_root_main(int argc, char **argv) { char *newroot, *console = NULL; struct stat st1, st2; struct statfs stfs; // Parse args (-c console) opt_complementary = "-2"; getopt32(argv, "c:", &console); argv += optind; // Change to new root directory and verify it's a different fs. newroot = *argv++; xchdir(newroot); if (lstat(".", &st1) || lstat("/", &st2) || st1.st_dev == st2.st_dev) { bb_error_msg_and_die("bad newroot %s", newroot); } rootdev = st2.st_dev; // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE // we mean it. (I could make this a CONFIG option, but I would get email // from all the people who WILL eat their filesystems.) if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) || (stfs.f_type != RAMFS_MAGIC && stfs.f_type != TMPFS_MAGIC) || getpid() != 1) { bb_error_msg_and_die("not rootfs"); } // Zap everything out of rootdev delete_contents("/"); // Overmount / with newdir and chroot into it. The chdir is needed to // recalculate "." and ".." links. if (mount(".", "/", NULL, MS_MOVE, NULL) || chroot(".")) bb_error_msg_and_die("error moving root"); xchdir("/"); // If a new console specified, redirect stdin/stdout/stderr to that. if (console) { close(0); xopen(console, O_RDWR); dup2(0, 1); dup2(0, 2); } // Exec real init. (This is why we must be pid 1.) execv(argv[0], argv); bb_perror_msg_and_die("bad init %s", argv[0]); }
int switch_root_main(int argc UNUSED_PARAM, char **argv) { char *newroot, *console = NULL; struct stat st; struct statfs stfs; dev_t rootdev; // Parse args (-c console) opt_complementary = "-2"; // minimum 2 params getopt32(argv, "+c:", &console); // '+': stop at first non-option argv += optind; newroot = *argv++; // Change to new root directory and verify it's a different fs xchdir(newroot); xstat("/", &st); rootdev = st.st_dev; xstat(".", &st); if (st.st_dev == rootdev || getpid() != 1) { // Show usage, it says new root must be a mountpoint // and we must be PID 1 bb_show_usage(); } // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE // we mean it. I could make this a CONFIG option, but I would get email // from all the people who WILL destroy their filesystems. if (stat("/init", &st) != 0 || !S_ISREG(st.st_mode)) { bb_error_msg_and_die("/init is not a regular file"); } statfs("/", &stfs); // this never fails if ((unsigned)stfs.f_type != RAMFS_MAGIC && (unsigned)stfs.f_type != TMPFS_MAGIC ) { bb_error_msg_and_die("root filesystem is not ramfs/tmpfs"); } // Zap everything out of rootdev delete_contents("/", rootdev); // Overmount / with newdir and chroot into it if (mount(".", "/", NULL, MS_MOVE, NULL)) { // For example, fails when newroot is not a mountpoint bb_perror_msg_and_die("error moving root"); } xchroot("."); // The chdir is needed to recalculate "." and ".." links /*xchdir("/"); - done in xchroot */ // If a new console specified, redirect stdin/stdout/stderr to it if (console) { close(0); xopen(console, O_RDWR); xdup2(0, 1); xdup2(0, 2); } // Exec real init execv(argv[0], argv); bb_perror_msg_and_die("can't execute '%s'", argv[0]); }