view toys/other/switch_root.c @ 1539:3e85af1f7e22 draft

First batch of sed tests. Only good for TEST_HOST=1 at the moment because the test infrastructure itself depends on sed, so if an unfinished sed is in the $PATH it goes boing. But hey, corner cases! I have... more.
author Rob Landley <>
date Wed, 29 Oct 2014 18:44:33 -0500
parents ffc7f606ce5b
line wrap: on
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/* switch_root.c - Switch from rootfs/initramfs to another filesystem
 * Copyright 2005 Rob Landley <>


  bool "switch_root"
  default y
    usage: switch_root [-c /dev/console] NEW_ROOT NEW_INIT...

    Use from PID 1 under initramfs to free initramfs, chroot to NEW_ROOT,
    and exec NEW_INIT.

    -c	Redirect console to device in NEW_ROOT
    -h	Hang instead of exiting on failure (avoids kernel panic)

#define FOR_switch_root
#include "toys.h"
#include <sys/vfs.h>

  char *console;

  dev_t rootdev;

static int del_node(struct dirtree *node)
  if (node->st.st_dev == TT.rootdev && dirtree_notdotdot(node)) {
    int flag = 0;
    if (S_ISDIR(node->st.st_mode)) {
      if (!node->again) return DIRTREE_COMEAGAIN;
      flag = AT_REMOVEDIR;
    unlinkat(dirtree_parentfd(node), node->name, flag);

  return 0;

void switch_root_main(void)
  char *newroot = *toys.optargs, **cmdline = toys.optargs+1;
  struct stat st1, st2;
  struct statfs stfs;
  int console = console; // gcc's "may be used" warnings are broken.

  if (getpid() != 1) error_exit("not pid 1");

  // Root filesystem we're leaving must be ramfs or tmpfs
  if (statfs("/", &stfs) ||
    (stfs.f_type != 0x858458f6 && stfs.f_type != 0x01021994))
    error_msg("not ramfs");
    goto panic;

  // New directory must be different filesystem instance
  if (chdir(newroot) || stat(".", &st1) || stat("/", &st2) ||
    st1.st_dev == st2.st_dev)
    error_msg("bad newroot '%s'", newroot);
    goto panic;

  // init program must exist and be an executable file
  if (stat("init", &st1) || !S_ISREG(st1.st_mode) || !(st1.st_mode&0100)) {
    error_msg("bad init");
    goto panic;

  if (TT.console && -1 == (console = open(TT.console, O_RDWR))) {
    perror_msg("bad console '%s'", TT.console);
    goto panic;
  // Ok, enough safety checks: wipe root partition.
  dirtree_read("/", del_node);

  if (TT.console) {
    int i;
    for (i=0; i<3; i++) if (console != i) dup2(console, i);
    if (console>2) close(console);
  execv(*cmdline, cmdline);
  perror_msg("Failed to exec '%s'", *cmdline);
  if (toys.optflags & FLAG_h) for (;;) wait(NULL);