Part 6: Entering Chroot and Building Additional Tools

Overview

You'll now enter a chroot (change root) environment to build additional temporary tools. The chroot isolates the build environment from the host system.

Prerequisites

Completed Part 5 (temporary tools)
Working as lfs user
$LFS variable set

Chroot Preparation

1. Change Ownership to Root

# Exit lfs user if logged in
exit

# As root, change ownership
sudo chown -R root:root $LFS/{usr,lib,var,etc,bin,sbin,tools}

# For 64-bit systems
sudo chown -R root:root $LFS/lib64

2. Create Virtual Filesystem Mount Points

# As root
sudo mkdir -pv $LFS/{dev,proc,sys,run}

3. Create Initial Device Nodes

# As root
sudo mknod -m 600 $LFS/dev/console c 5 1
sudo mknod -m 666 $LFS/dev/null c 1 3

4. Mount Virtual Filesystems

# As root
sudo mount -v --bind /dev $LFS/dev
sudo mount -vt devpts devpts -o gid=5,mode=0620 $LFS/dev/pts
sudo mount -vt proc proc $LFS/proc
sudo mount -vt sysfs sysfs $LFS/sys
sudo mount -vt tmpfs tmpfs $LFS/run

# If /dev/shm is a symlink
if [ -h $LFS/dev/shm ]; then
  install -v -d -m 1777 $LFS$(realpath /dev/shm)
else
  sudo mount -vt tmpfs -o nosuid,nodev tmpfs $LFS/dev/shm
fi

Enter Chroot

Enter Chroot Environment

# As root
sudo chroot "$LFS" /usr/bin/env -i \
    HOME=/root \
    TERM="$TERM" \
    PS1='(lfs chroot) \u:\w\$ ' \
    PATH=/usr/bin:/usr/sbin \
    MAKEFLAGS="-j$(nproc)" \
    TESTSUITEFLAGS="-j$(nproc)" \
    /bin/bash --login

You are now inside the LFS chroot environment!

Create Essential Directories

# Inside chroot
mkdir -pv /{boot,home,mnt,opt,srv}

mkdir -pv /etc/{opt,sysconfig}
mkdir -pv /lib/firmware
mkdir -pv /media/{floppy,cdrom}
mkdir -pv /usr/{,local/}{include,src}
mkdir -pv /usr/local/{bin,lib,sbin}
mkdir -pv /usr/{,local/}share/{color,dict,doc,info,locale,man}
mkdir -pv /usr/{,local/}share/{misc,terminfo,zoneinfo}
mkdir -pv /usr/{,local/}share/man/man{1..8}
mkdir -pv /var/{cache,local,log,mail,opt,spool}
mkdir -pv /var/lib/{color,misc,locate}

ln -sfv /run /var/run
ln -sfv /run/lock /var/lock

install -dv -m 0750 /root
install -dv -m 1777 /tmp /var/tmp

Create Essential Files and Symlinks

# Create mtab symlink
ln -sv /proc/self/mounts /etc/mtab

# Create /etc/hosts
cat > /etc/hosts << "EOF"
127.0.0.1  localhost localhost.localdomain
::1        localhost ip6-localhost ip6-loopback
ff02::1    ip6-allnodes
ff02::2    ip6-allrouters
EOF

# Create /etc/passwd
cat > /etc/passwd << "EOF"
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/dev/null:/usr/bin/false
daemon:x:6:6:Daemon User:/dev/null:/usr/bin/false
messagebus:x:18:18:D-Bus Message Daemon User:/run/dbus:/usr/bin/false
systemd-journal-gateway:x:73:73:systemd Journal Gateway:/:/usr/bin/false
systemd-journal-remote:x:74:74:systemd Journal Remote:/:/usr/bin/false
systemd-journal-upload:x:75:75:systemd Journal Upload:/:/usr/bin/false
systemd-network:x:76:76:systemd Network Management:/:/usr/bin/false
systemd-resolve:x:77:77:systemd Resolver:/:/usr/bin/false
systemd-timesync:x:78:78:systemd Time Synchronization:/:/usr/bin/false
systemd-coredump:x:79:79:systemd Core Dumper:/:/usr/bin/false
uuidd:x:80:80:UUID Generation Daemon User:/dev/null:/usr/bin/false
systemd-oom:x:81:81:systemd Out Of Memory Daemon:/:/usr/bin/false
nobody:x:65534:65534:Unprivileged User:/dev/null:/usr/bin/false
EOF

# Create /etc/group
cat > /etc/group << "EOF"
root:x:0:
bin:x:1:daemon
sys:x:2:
kmem:x:3:
tape:x:4:
tty:x:5:
daemon:x:6:
floppy:x:7:
disk:x:8:
lp:x:9:
dialout:x:10:
audio:x:11:
video:x:12:
utmp:x:13:
cdrom:x:15:
adm:x:16:
messagebus:x:18:
systemd-journal:x:23:
input:x:24:
mail:x:34:
kvm:x:61:
systemd-journal-gateway:x:73:
systemd-journal-remote:x:74:
systemd-journal-upload:x:75:
systemd-network:x:76:
systemd-resolve:x:77:
systemd-timesync:x:78:
systemd-coredump:x:79:
uuidd:x:80:
systemd-oom:x:81:
wheel:x:97:
users:x:999:
nogroup:x:65534:
EOF

# Initialize log files
touch /var/log/{btmp,lastlog,faillog,wtmp}
chgrp -v utmp /var/log/lastlog
chmod -v 664  /var/log/lastlog
chmod -v 600  /var/log/btmp

Build Additional Temporary Tools (Chapter 7)

Now build these tools inside chroot:

Gettext-0.26
Bison-3.8.2
Perl-5.42.0
Python-3.13.7
Texinfo-7.2
Util-linux-2.41.1

1. Gettext-0.26

cd /sources
tar -xf gettext-0.26.tar.xz
cd gettext-0.26

./configure --disable-shared

make
cp -v gettext-tools/src/{msgfmt,msgmerge,xgettext} /usr/bin

cd /sources
rm -rf gettext-0.26

2. Bison-3.8.2

cd /sources
tar -xf bison-3.8.2.tar.xz
cd bison-3.8.2

./configure --prefix=/usr \
            --docdir=/usr/share/doc/bison-3.8.2

make
make install

cd /sources
rm -rf bison-3.8.2

3. Perl-5.42.0

cd /sources
tar -xf perl-5.42.0.tar.xz
cd perl-5.42.0

sh Configure -des \
             -D prefix=/usr \
             -D vendorprefix=/usr \
             -D useshrplib \
             -D privlib=/usr/lib/perl5/5.42/core_perl \
             -D archlib=/usr/lib/perl5/5.42/core_perl \
             -D sitelib=/usr/lib/perl5/5.42/site_perl \
             -D sitearch=/usr/lib/perl5/5.42/site_perl \
             -D vendorlib=/usr/lib/perl5/5.42/vendor_perl \
             -D vendorarch=/usr/lib/perl5/5.42/vendor_perl

make
make install

cd /sources
rm -rf perl-5.42.0

4. Python-3.13.7

cd /sources
tar -xf Python-3.13.7.tar.xz
cd Python-3.13.7

./configure --prefix=/usr \
            --enable-shared \
            --without-ensurepip

make
make install

cd /sources
rm -rf Python-3.13.7

5. Texinfo-7.2

cd /sources
tar -xf texinfo-7.2.tar.xz
cd texinfo-7.2

./configure --prefix=/usr

make
make install

cd /sources
rm -rf texinfo-7.2

6. Util-linux-2.41.1

cd /sources
tar -xf util-linux-2.41.1.tar.xz
cd util-linux-2.41.1

mkdir -pv /var/lib/hwclock

./configure --libdir=/usr/lib \
            --runstatedir=/run \
            --disable-chfn-chsh \
            --disable-login \
            --disable-nologin \
            --disable-su \
            --disable-setpriv \
            --disable-runuser \
            --disable-pylibmount \
            --disable-liblastlog2 \
            --disable-static \
            --without-python \
            ADJTIME_PATH=/var/lib/hwclock/adjtime \
            --docdir=/usr/share/doc/util-linux-2.41.1

make
make install

cd /sources
rm -rf util-linux-2.41.1

Clean Up and Backup

Strip Debug Symbols

# Save space by stripping debugging symbols
strip --strip-debug /usr/lib/*
strip --strip-unneeded /usr/{,s}bin/*
strip --strip-unneeded /tools/bin/*

# Remove documentation (optional - saves space)
rm -rf /usr/share/{info,man,doc}/*

Clean Up

# Remove temporary files
find /usr/{lib,libexec} -name \*.la -delete
rm -rf /tools

Create Backup (Recommended)

Exit chroot and create a backup:

# Exit chroot
exit

# As root on host
cd $LFS
sudo tar -cJpf $HOME/lfs-temp-tools-12.4.tar.xz .

# Later, to restore:
# cd $LFS
# sudo rm -rf ./*
# sudo tar -xpf $HOME/lfs-temp-tools-12.4.tar.xz

Re-entering Chroot

If you need to exit and re-enter chroot:

# Remount virtual filesystems
sudo mount -v --bind /dev $LFS/dev
sudo mount -vt devpts devpts -o gid=5,mode=0620 $LFS/dev/pts
sudo mount -vt proc proc $LFS/proc
sudo mount -vt sysfs sysfs $LFS/sys
sudo mount -vt tmpfs tmpfs $LFS/run

# Enter chroot
sudo chroot "$LFS" /usr/bin/env -i \
    HOME=/root \
    TERM="$TERM" \
    PS1='(lfs chroot) \u:\w\$ ' \
    PATH=/usr/bin:/usr/sbin \
    MAKEFLAGS="-j$(nproc)" \
    TESTSUITEFLAGS="-j$(nproc)" \
    /bin/bash --login

Verification

Verify you're in chroot:

# Should show only chroot environment
echo $PATH
# Output: /usr/bin:/usr/sbin

# Verify tools exist
which bash gcc make

Next Steps

Chroot environment ready! Proceed to:

Part 7: Build complete LFS system (70+ packages)
Part 8: System configuration
Part 9: Kernel and bootloader

Important Notes

Always work inside chroot from now on
Don't exit chroot until Part 9 complete
If you must exit, remember to remount virtual filesystems
Backup regularly

Part 06 Chroot Environment