source: chapter07/introduction.xml

Last change on this file was a8f3814a, checked in by Xi Ruoyao <xry111@…>, 14 months ago

kernfs: technically, they are not needed for chroot

Chroot command itself does not require kernel VFS mounted. You can mount
/proc, /sys, and /run after entering chroot with
"mount -v -t proc proc /proc" etc. For /dev, if the host kernel
supports devtmpfs, you can also mount /dev in chroot with
"mount -v -t devtmpfs devtmpfs /dev". Even if the host does not support
devtmpfs, it's still possible to mount /proc in chroot, then use
"mount --bind /proc/1/dev /dev".

It's just LFS editors decide to mount them before chroot. So reword
some untrue assertions.

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[673b0d8]1<?xml version="1.0" encoding="ISO-8859-1"?>
[b06ca36]2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "" [
[673b0d8]4 <!ENTITY % general-entities SYSTEM "../general.ent">
5 %general-entities;
[ce335792]8<sect1 id="ch-tools-introduction-chroot">
[d781ffb]9 <?dbhtml filename="introduction.html"?>
[d781ffb]11 <title>Introduction</title>
[387a32af]13 <para>This chapter shows how to build the last missing bits of the temporary
[52ddd6c]14 system: the tools needed to build the various packages. Now
[305c970]15 that all circular dependencies have been resolved, a <quote>chroot</quote>
16 environment, completely isolated from the host operating system (except for
17 the running kernel), can be used for the build.</para>
19 <para>For proper operation of the isolated environment, some communication
[52ddd6c]20 with the running kernel must be established. This is done via the
[a8f3814a]21 so-called <emphasis>Virtual Kernel File Systems</emphasis>, which will be
[52ddd6c]22 mounted before entering the chroot environment. You may want to verify
23 that they are mounted by issuing the <command>findmnt</command> command.</para>
25 <para>Until <xref linkend="ch-tools-chroot"/>, the commands must be
26 run as <systemitem class="username">root</systemitem>, with the
27 <envar>LFS</envar> variable set. After entering chroot, all commands
[e286d8db]28 are run as &root;, fortunately without access to the OS of the computer
[387a32af]29 you built LFS on. Be careful anyway, as it is easy to destroy the whole
[52ddd6c]30 LFS system with bad commands.</para>
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