sys-utils/pivot_root.8.adoc

   1 //po4a: entry man manual
   2 = pivot_root(8)
   3 :doctype: manpage
   4 :man manual: System Administration
   5 :man source: util-linux {release-version}
   6 :page-layout: base
   7 :command: pivot_root
   8
   9 == NAME
  10
  11 pivot_root - change the root filesystem
  12
  13 == SYNOPSIS
  14
  15 *pivot_root* _new_root_ _put_old_
  16
  17 == DESCRIPTION
  18
  19 *pivot_root* moves the root file system of the current process to the directory _put_old_ and makes _new_root_ the new root file system. Since *pivot_root*(8) simply calls *pivot_root*(2), we refer to the man page of the latter for further details.
  20
  21 Note that, depending on the implementation of *pivot_root*, root and current working directory of the caller may or may not change. The following is a sequence for invoking *pivot_root* that works in either case, assuming that *pivot_root* and *chroot* are in the current *PATH*:
  22
  23 ....
  24 cd new_root
  25 pivot_root . put_old
  26 exec chroot . command
  27 ....
  28
  29 Note that *chroot* must be available under the old root and under the new root, because *pivot_root* may or may not have implicitly changed the root directory of the shell.
  30
  31 Note that *exec chroot* changes the running executable, which is necessary if the old root directory should be unmounted afterwards. Also note that standard input, output, and error may still point to a device on the old root file system, keeping it busy. They can easily be changed when invoking *chroot* (see below; note the absence of leading slashes to make it work whether *pivot_root* has changed the shell's root or not).
  32
  33 == OPTIONS
  34
  35 include::man-common/help-version.adoc[]
  36
  37 == EXAMPLE
  38
  39 Change the root file system to _/dev/hda1_ from an interactive shell:
  40
  41 ....
  42 mount /dev/hda1 /new-root
  43 cd /new-root
  44 pivot_root . old-root
  45 exec chroot . sh <dev/console >dev/console 2>&1
  46 umount /old-root
  47 ....
  48
  49 Mount the new root file system over NFS from 10.0.0.1:/my_root and run *init*:
  50
  51 ....
  52 ifconfig lo 127.0.0.1 up   # for portmap
  53 # configure Ethernet or such
  54 portmap   # for lockd (implicitly started by mount)
  55 mount -o ro 10.0.0.1:/my_root /mnt
  56 killall portmap   # portmap keeps old root busy
  57 cd /mnt
  58 pivot_root . old_root
  59 exec chroot . sh -c 'umount /old_root; exec /sbin/init' \
  60   <dev/console >dev/console 2>&1
  61 ....
  62
  63 == SEE ALSO
  64
  65 *chroot*(1),
  66 *pivot_root*(2),
  67 *mount*(8),
  68 *switch_root*(8),
  69 *umount*(8)
  70
  71 include::man-common/bugreports.adoc[]
  72
  73 include::man-common/footer.adoc[]
  74
  75 ifdef::translation[]
  76 include::man-common/translation.adoc[]
  77 endif::[]