Alpine Linux in a chroot: Difference between revisions

From Alpine Linux
(List default initscripts to add to make the system bootable)
Line 82: Line 82:
You can now chroot:
You can now chroot:
{{Cmd|chroot ${chroot_dir} /bin/sh -l}}
{{Cmd|chroot ${chroot_dir} /bin/sh -l}}
To make the system actually bootable, we need to add some initscripts to appropriate runlevels:
{{Cmd|rc-update add devfs sysinit
rc-update add dmesg sysinit
rc-update add mdev sysinit
rc-update add hwclock boot
rc-update add modules boot
rc-update add sysctl boot
rc-update add hostname boot
rc-update add bootmisc boot
rc-update add syslog boot
rc-update add mount-ro shutdown
rc-update add killprocs shutdown
rc-update add savecache shutdown}}


Alpine Linux has a great meta-package for building Alpine packages from source available called alpine-sdk. To install, run:
Alpine Linux has a great meta-package for building Alpine packages from source available called alpine-sdk. To install, run:

Revision as of 13:49, 3 October 2014

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:

Set up APK

Download the latest apk static package:

Tip: In the command below, replace x86_64 with x86 if running on a 32 bit installation
Warning: You will need Kernel version 2.6.22 or later to use apk-tools-static


wget ${mirror}/v3.0/main/x86_64/apk-tools-static-2.4.4-r0.apk

.apk packages are just gzipped tarballs, unpack using:

tar -xzf apk-tools-static-2.4.4-r0.apk

Install the alpine base installation onto the chroot

./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

Tip: Manually creating devices is not needed if you choose to mount /dev of the hosts in the chroot described later.

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

To make the system actually bootable, we need to add some initscripts to appropriate runlevels:

rc-update add devfs sysinit rc-update add dmesg sysinit rc-update add mdev sysinit rc-update add hwclock boot rc-update add modules boot rc-update add sysctl boot rc-update add hostname boot rc-update add bootmisc boot rc-update add syslog boot rc-update add mount-ro shutdown rc-update add killprocs shutdown rc-update add savecache shutdown

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.

Note: Maybe you are able to use this script on other distribution but this is not tested.

Troubleshooting

WARNING: Ignoring APKINDEX.xxxx.tar.gz

Make sure ${chroot_dir}/etc/apk/repositories is valid and inside the chroot run:

apk update