1PIVOT_ROOT(8)                Maintenance Commands                PIVOT_ROOT(8)
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NAME

6       pivot_root - change the root file system
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SYNOPSIS

9       pivot_root new_root put_old
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DESCRIPTION

12       pivot_root  moves  the  root  file system of the current process to the
13       directory put_old and makes new_root the new root file  system.   Since
14       pivot_root(8)  simply  calls pivot_root(2), we refer to the man page of
15       the latter for further details.
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17       Note that, depending on the implementation of pivot_root, root and  cwd
18       of  the  caller  may or may not change. The following is a sequence for
19       invoking pivot_root that works in either case, assuming that pivot_root
20       and chroot are in the current PATH:
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22       cd new_root
23       pivot_root . put_old
24       exec chroot . command
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26       Note that chroot must be available under the old root and under the new
27       root, because pivot_root may or may not  have  implicitly  changed  the
28       root directory of the shell.
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30       Note  that  exec chroot changes the running executable, which is neces‐
31       sary if the old root directory should be  unmounted  afterwards.   Also
32       note that standard input, output, and error may still point to a device
33       on the old root file system,  keeping  it  busy.  They  can  easily  be
34       changed  when  invoking  chroot (see below; note the absence of leading
35       slashes to make it work whether pivot_root has changed the shell's root
36       or not).
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EXAMPLES

39       Change the root file system to /dev/hda1 from an interactive shell:
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41       mount /dev/hda1 /new-root
42       cd /new-root
43       pivot_root . old-root
44       exec chroot . sh <dev/console >dev/console 2>&1
45       umount /old-root
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47       Mount  the new root file system over NFS from 10.0.0.1:/my_root and run
48       init:
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50       ifconfig lo 127.0.0.1 up   # for portmap
51       # configure Ethernet or such
52       portmap   # for lockd (implicitly started by mount)
53       mount -o ro 10.0.0.1:/my_root /mnt
54       killall portmap   # portmap keeps old root busy
55       cd /mnt
56       pivot_root . old_root
57       exec chroot . sh -c 'umount /old_root; exec /sbin/init' \
58         <dev/console >dev/console 2>&1
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SEE ALSO

61       chroot(1), mount(8), pivot_root(2), umount(8)
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AVAILABILITY

64       The pivot_root command is part of  the  util-linux-ng  package  and  is
65       available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
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69Linux                            Feb 23, 2000                    PIVOT_ROOT(8)
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