Alpine Linux 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. The guide can also be used to install Alpine Linux from a non-Alpine Linux livecd such as Ubuntu or System rescue CD. This example installation of Alpine Linux in a chroot will work with the lastest release. But it's also possible to make a chroot with edge or older releases of Alpine Linux to test backports.
Requirements
For the base Alpine Linux you will only need around 6MB of free space; though to build packages you'll need at least 500 MB.
Prerequisites
The variables below:
- ${chroot_dir} = Should point to the chroot directory where you
- ${mirror} = Should be replaced with one of the available Alpine Linux mirrors.
Set up APK
Download the latest apk static package:
wget http://dl-3.alpinelinux.org/alpine/v3.0/main/x86_64/apk-tools-static-2.4.4-r0.apk
.apk packages are just gzipped tarballs, unpack using:
mkdir apk-tools-static tar -xzf apk-tools-static-2.4.4-r0.apk -C apk-tools-static
Install the alpine base installation onto the chroot
./apk-tools-static/sbin/apk.static -X ${mirror}/v3.0/main -U --allow-untrusted --root ${chroot_dir} --initdb add alpine-base
Set up the chroot
Set up some devices in the chroot
mknod -m 666 ${chroot_dir}/dev/full c 1 7 mknod -m 666 ${chroot_dir}/dev/ptmx c 5 2 mknod -m 644 ${chroot_dir}/dev/random c 1 8 mknod -m 644 ${chroot_dir}/dev/urandom c 1 9 mknod -m 666 ${chroot_dir}/dev/zero c 1 5 mknod -m 666 ${chroot_dir}/dev/tty c 5 0
If you need SCSI disc access:
mknod -m 666 ${chroot_dir}/dev/sda b 8 0 mknod -m 666 ${chroot_dir}/dev/sda1 b 8 1 mknod -m 666 ${chroot_dir}/dev/sda2 b 8 2 mknod -m 666 ${chroot_dir}/dev/sda3 b 8 3 mknod -m 666 ${chroot_dir}/dev/sda4 b 8 4 mknod -m 666 ${chroot_dir}/dev/sda5 b 8 5 mknod -m 666 ${chroot_dir}/dev/sda6 b 8 6 mknod -m 666 ${chroot_dir}/dev/sdb b 8 16 mknod -m 666 ${chroot_dir}/dev/sda1 b 8 17 mknod -m 666 ${chroot_dir}/dev/sda2 b 8 18 mknod -m 666 ${chroot_dir}/dev/sda3 b 8 19 mknod -m 666 ${chroot_dir}/dev/sda4 b 8 20 mknod -m 666 ${chroot_dir}/dev/sda5 b 8 21 mknod -m 666 ${chroot_dir}/dev/sda6 b 8 22
A resolv.conf is needed for name resolution:
cp /etc/resolv.conf ${chroot_dir}/etc/ mkdir -p ${chroot_dir}/root
If you don't want to copy the resolv.conf from the local machine, you can create a new one using Googles DNS servers:
echo 'nameserver 8.8.8.8' > ${chroot_dir}/etc/resolv.conf
Set up APK mirror:
mkdir -p ${chroot_dir}/etc/apk echo "${mirror}/v3.0/main" > ${chroot_dir}/etc/apk/repositories
Entering your chroot
At this point, Alpine has been succesfully installed onto the chroot directory. Before you chroot in you will probably want to mount /proc and /sys in the chroot:
mount -t proc none ${chroot_dir}/proc mount -o bind /sys ${chroot_dir}/sys
If you don't want to create special device files yourself, mount the hosts device directory onto the chroot:
mount -o bind /dev ${chroot_dir}/dev
You can now chroot:
chroot ${chroot_dir} /bin/sh -l
Alpine Linux has a great meta-package for building Alpine packages from source available called alpine-sdk. To install, run:
apk add alpine-sdk
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
Alpine Linux in a chroot on Fedora
If you want to generate a chroot on a Fedora based system, you can use this script.