Alpine Linux in a chroot

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Setting up a 'edge' build environment in a chroot

This document explains how to set up an Alpine build environment in a chroot under a "normal" Linux distro, such as Arch, Debian, Fedora, Gentoo, or Ubuntu. Once inside the chroot environment, you can build, debug and run alpine packages.

Introduction

You will need a few Gigabytes to have enough pace for kernel compiling and storing all the binary packages and iso image.

Create a build environment

We are setting up our Build Environment in chroot.

Note: The variables below:

  • ${build_dir} = You can name it whatever you like.
  • ${mirror} = Should be replaced with one of the available alpine-mirrors:



Lets start by geting the latest apk static binary:

wget ${mirror}/v1.9/apk.static
chmod +x ./apk.static

Verify you have apk-tools 2.0_rc1 or later:

./apk.static --version
  apk-tools 2.0_rc1

We are setting up a basic chroot:

mkdir ${build_dir}
sudo ./apk.static --repo ${mirror}/v1.9/packages/main -U --allow-untrusted --root ${build_dir} --initdb add alpine-base alpine-sdk
mkdir -p ./${build_dir}/proc
sudo mount --bind /proc ./${build_dir}/proc

Lets setup our needed devices:

sudo mknod -m 666 ./${build_dir}/dev/full c 1 7
sudo mknod -m 666 ./${build_dir}/dev/ptmx c 5 2
sudo mknod -m 644 ./${build_dir}/dev/random c 1 8
sudo mknod -m 644 ./${build_dir}/dev/urandom c 1 9
sudo mknod -m 666 ./${build_dir}/dev/zero c 1 5
sudo mknod -m 666 ./${build_dir}/dev/tty c 5 0

We need or dns servers and root dir:

sudo cp /etc/resolv.conf ./${build_dir}/etc/
mkdir -p ./${build_dir}/root

We are setting up apk mirrors:

sudo mkdir -p ./${build_dir}/etc/apk
sudo su
echo "${mirror}/v1.9/packages/main" > ./${build_dir}/etc/apk/repositories
exit

At this point you should be able to enter your chroot:

sudo chroot ./${build_dir} /bin/sh -l

If you are using Alpine as a Native build system you will have to make sure that chroot can run chmod. Add following to /etc/sysctl.conf

kernel.grsecurity.chroot_deny_chmod = 0

Then run the following command

sysctl -p


Now you can move on to creating packages for Alpine.