source: BOOK/temp-system/common/choose.xml@ 39c0cd7

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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../../general.ent">
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<sect1 id="ch-temp-system-choose">
  <?dbhtml filename="choose.html"?>

  <title>To Boot or to Chroot?</title>

  <para os="a"> There are two different ways you can proceed from this point
  to build the final system. You can build a kernel, a bootloader, and
  a few other utilities, boot into the temporary system, and build the
  rest there. Alternatively, you can chroot into the temporary system.</para>

  <para os="b">The <command>chroot</command> (change root) program is used to enter
  a virtual environment and start a new shell whose root directory will be set
  to the CLFS partition. This is very similar to rebooting and instructing the
  kernel to mount the CLFS partition as the root partition.
  The major advantage is that <quote>chrooting</quote> allows the builder to
  continue using the host while CLFS is being built. While waiting for package
  compilation to complete, a user can switch to a different virtual console
  (VC) or X desktop and continue using the computer as normal.</para>

  <para os="c">Some systems cannot be built by chrooting so they must be
  booted instead. Generally, if you building for a different arch than
  the host system, you must reboot because the kernel will likely not
  support the target machine. Booting involves installing a few
  additional packages that are needed for bootup, installing
  boot-scripts, and building a miminal kernel.<!-- We also describe some
  alternative booting methods in <xref linkend="ch-boot-whatnext"/> -->
  The boot method is needed when you are building on a different
  architecture. For example, if you are building a PowerPC system from
  an x86, you can't chroot. The chroot method is for when you are
  building on the same architecture. If you are building on, and for,
  an x86 system, you can simply chroot. The rule of thumb here is if
  the architectures match and you are running the same series kernel
  you can just chroot. If you aren't running the same series kernel, or are
  wanting to run a different ABI, you will need to use the boot option.</para>

  <para os="d">If you are in any doubt about this, you can try the following
 commands to see if you can chroot:</para>

<screen os="e"><userinput>/tools/lib/libc.so.6
/tools/bin/gcc -v</userinput></screen>

  <para os="f">If either of these commands fail, you will have to follow the boot
  method.</para>

  <para os="g">To chroot, you will also need a Linux Kernel-2.6.32 or greater
  (having been compiled with GCC-4.1.2 or greater). The reason for the
  kernel version requirement is that Glibc is built to generate the library
  for the smallest version of the Linux kernel expected to be supported.</para>

  <para os="h">To check your kernel version, run <command>cat /proc/version</command>
  - if it does not say that you are running a 2.6.32 or later Linux kernel,
  compiled with GCC 4.1.2 or later, you cannot chroot.</para>

  <para os="i">For the boot method, follow <xref linkend="chapter-boot"/>.</para>

  <para os="j">For the chroot method, follow <xref linkend="chapter-chroot"/>.</para>

</sect1>