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Re: question of chroot

From: Bob Proulx
Subject: Re: question of chroot
Date: Sat, 11 Jan 2003 11:04:20 -0700
User-agent: Mutt/1.4i

mydownload my <address@hidden> [2003-01-12 00:12:18 +0800]:
> I am a linux user.I want to ask a question about "chroot".
> When I use "chroot" command(for example:chroot /root),a error display:
> chroot: cannot execute /bin/bash: No such file or directory

       Run COMMAND with root directory set to NEWROOT.
       If no command is  given,  run  ``${SHELL}  -i''  (default:

The chroot command changes the root of your filesystem to the
specified location.  If you are not specifying a command then the
default is /bin/sh.

  chroot /root

Is equivalent to:

  chroot /root /bin/sh -i

Do you have a file '/root/bin/sh' and all of the shared libraries and
support filesystem needed to allow that to work?  One would not
normally create a filesystem at /root.  That is a terrible location
for that purpose.

The chroot command has very specific behavior which people can use for
many different purposes.  Such as creating an area for another
operating system on the same disk as your present operating system.
You can chroot to the other system and perform testing and other uses.

If you wanted to create a chroot area, here is one method.  As one
example, once in this area one could update their operating system
components in the chroot, without affecting the outer filesystem, and
experiment with new commands and functionality.  For example, if one
of my install packages had a really bad bug and did 'rm -rf /' this
would only affect the chroot area and my underlying system hosting it
would be unaffected.

  mkdir -p /chrootarea
  cp -av /bin /dev /etc /home /lib /root /sbin /tmp /usr /var /chrootarea/
  chroot /chrootarea su -

But don't confuse the idea of a chroot area as a security area.  Root
processes in the chroot area can easily escape the chroot jail.


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