Installing a 32bit build chroot

By cormander

Sometimes it’s just easier to have a 32bit system to build 32bit packages on, but we don’t always have that option. And creating a virtual machine may just be too much overhead. After all, you just want some 32bit packages to be built on your 64bit system and not have to worry about multi-arch problems at build time. Here is how I usually solve the problem.

First, fool rpm into thinking this is a 32bit system:

mv /etc/rpm/platform /etc/rpm/platform.orig

echo i686-redhat-linux > /etc/rpm/platform

Then make your target directory. In this case I’m doing Fedora 11:

mkdir -p /var/distro/Fedora11.i386
cd /var/distro/Fedora11.i386

Now you’re in the directory you’re going to install in. This is important as I reference this directory throughout this tutorial as $(pwd). If you cd out of this directory in the middle of these steps, you’re bound to run into problems.

Setup some basic items:

mkdir -p dev proc sys root etc var/{log/yum,lib/rpm}

mount -t proc none proc
mount -t sysfs none sys

cp /etc/resolv.conf etc/

You don’t need an fstab, but no harm in creating one. You’ll actually avoid some meaningless errors by creating it:

cat << EOF > etc/fstab
/dev/xvda2              /                       ext3    defaults        1 1
/dev/xvda1              /boot                   ext2    defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
EOF

Create your /dev/null device and give it the mark of the beast:

mknod dev/null c 1 3
chmod 666 dev/null

For Fedora 11:

rpm --root $(pwd) --import http://mirrors.kernel.org/fedora/releases/11/Fedora/i386/os/RPM-GPG-KEY-fedora
wget http://mirrors.kernel.org/fedora/releases/11/Fedora/i386/os/Packages/fedora-release-11-1.noarch.rpm
rpm --root $(pwd) --nodeps -ivh fedora-release-11-1.noarch.rpm

For CentOS 5:

rpm --root $(pwd) --import http://mirrors.kernel.org/centos/5/os/i386/RPM-GPG-KEY-CentOS-5
wget http://mirrors.kernel.org/centos/5/os/i386/CentOS/centos-release-5-3.el5.centos.1.i386.rpm
rpm --root $(pwd) --nodeps -ivh centos-release-5-3.el5.centos.1.i386.rpm

Now install. This may take a while, depending on your internet connection speed.

yum --installroot=$(pwd) -y install kernel rootfiles passwd vim-enhanced wget strace grub \
    openssh-server openssh-clients gcc patchutils diffutils gcc make rpm-build rpmdevtools sudo yum

Now wipe out the rpm db, it’ll get rebuilt next time it’s used:

rm -f var/lib/rpm/__db.00*

Lastly, don’t forget to restore your rpm arch configuration:

mv /etc/rpm/platform.orig /etc/rpm/platform

Now you can do this:

setarch i686 chroot $(pwd)

Anything you build while in this chroot is guaranteed to be completely 32bit and have no 64bit related build problems.