pivot_root.c 1.7 KB

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  1. /* vi: set sw=4 ts=4: */
  2. /*
  3. * pivot_root.c - Change root file system. Based on util-linux 2.10s
  4. *
  5. * busyboxed by Evin Robertson
  6. * pivot_root syscall stubbed by Erik Andersen, so it will compile
  7. * regardless of the kernel being used.
  8. *
  9. * Licensed under GPLv2, see file LICENSE in this source tree.
  10. */
  11. //config:config PIVOT_ROOT
  12. //config: bool "pivot_root (1.1 kb)"
  13. //config: default y
  14. //config: select PLATFORM_LINUX
  15. //config: help
  16. //config: The pivot_root utility swaps the mount points for the root filesystem
  17. //config: with some other mounted filesystem. This allows you to do all sorts
  18. //config: of wild and crazy things with your Linux system and is far more
  19. //config: powerful than 'chroot'.
  20. //config:
  21. //config: Note: This is for initrd in linux 2.4. Under initramfs (introduced
  22. //config: in linux 2.6) use switch_root instead.
  23. //applet:IF_PIVOT_ROOT(APPLET_NOFORK(pivot_root, pivot_root, BB_DIR_SBIN, BB_SUID_DROP, pivot_root))
  24. //kbuild:lib-$(CONFIG_PIVOT_ROOT) += pivot_root.o
  25. //usage:#define pivot_root_trivial_usage
  26. //usage: "NEW_ROOT PUT_OLD"
  27. //usage:#define pivot_root_full_usage "\n\n"
  28. //usage: "Move the current root file system to PUT_OLD and make NEW_ROOT\n"
  29. //usage: "the new root file system"
  30. #include "libbb.h"
  31. extern int pivot_root(const char *new_root, const char *put_old);
  32. int pivot_root_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  33. int pivot_root_main(int argc, char **argv)
  34. {
  35. if (argc != 3)
  36. bb_show_usage();
  37. /* NOFORK applet. Hardly matters wrt performance, but code is trivial */
  38. if (pivot_root(argv[1], argv[2]) < 0) {
  39. /* prints "pivot_root: <strerror text>" */
  40. bb_perror_nomsg_and_die();
  41. }
  42. return EXIT_SUCCESS;
  43. }