Unattended Boot and Install

Introduction

This wiki describes a modified version of the original method I posted for Headless installation on a Raspberry Pi. While the original version worked for other architectures, like x86_64, it was targeted at and posted in the Raspberry Pi section since that was my primary focus at the time. Revisions to that page by other authors removed the mention of x86_64 altogether so this version will be more generally written in the hopes that it will be easier to find and that it's applicability will be clearer.

Additionally, this version improves upon the original (in my opinion) by automatically logging in the root user and optionally running a shell script. This provides a means to perform unattended installations or other scripted tasks and does not require modification of the stock Alpine installation media / files.

The following functionality is provided:

• Automatic DHCP configuration of a network interface, either wired or wireless
• Automatic configuration of sshd with password-less root login enabled
• Automatic login of the root user on tty7
• Automatic script execution (optional)

This is accomplished by using an overlay file that Alpine extracts at boot. Download a pre-built overlay file here.

Note: I've removed the draft notice from the top of this page but additional testing is needed. Use at your own risk.

Basic Use

For Alpine supported Raspberry Pi models:

1. Download the applicable Alpine installation tarball and extract it to an SD card formatted with a single FAT partition.
2. Copy the headless.apkovl.tar.gz file to the root of the SD card.
3. Optionally, create a file named wifi.txt in the root of the SD card. See below for file format.
4. Optionally, create a file named unattended.sh in the root of the SD card. See below for an example.
5. Boot the Pi with the SD card.

For other architectures (tested on various x86_64 hardware and a Qemu VM)

1. Download the applicable Alpine installation file and write it to usb stick or other media as needed.
2. Copy the headless.apkovl.tar.gz file to a second usb stick or other media separate from the installation media.
3. Optionally, create a file named wifi.txt in the root of second media. See below for file format.
4. Optionally, create a file named unattended.sh in the root of the second media. See below for an example.
5. Boot the device with both the installation and the secondary media connected.

For basic interactive ssh access, only the headless.apkovl.tar.gz file is required. The wifi.txt file can be omitted if wired ethernet is used. The unattended.sh file can be omitted.

Wifi Support

Create a text file named wifi.txt with the SSID and Password on the first line of the file:

SSID Password

Example Scripts

If a shell script named unattended.sh is found in the root of the same media that contains the headless.apkovl.tar.gz file, it will be executed (sourced) by the root user after the auto login occurs on tty7. This can be used to script the installation of Alpine to local disk for example. Note too, that since network is available, the unattended.sh script can also just fetch and execute another script from the local network or internet, if available.

I've experimented with different installation scripts. The first is derived from the setup-alpine script. It skips the sshd and network interface setup scripts as they are already configured and running.

Contents of unattended.sh

KEYMAPOPTS="us us" HOSTNAMEOPTS="-n alpine-test" TIMEZONEOPTS="-z UTC" NTPOPTS="-c busybox" APKREPOSOPTS="-r" DISKOPTS="-m sys /dev/mmcblk0" source /lib/libalpine.sh setup-keymap ${KEYMAPOPTS} setup-hostname ${HOSTNAMEOPTS} setup-timezone ${TIMEZONEOPTS} rc-update add networking boot rc-update add urandom boot for svc in acpid cron crond; do if rc-service --exists $svc; then rc-update add $svc fi done rc-service hostname restart _dn=$(sed -n \ -e '/^domain[[:space:]][[:space:]]*/{s///;s/\([^[:space:]]*\).*$/\1/;h;}' \ -e '/^search[[:space:]][[:space:]]*/{s///;s/\([^[:space:]]*\).*$/\1/;h;}' \ -e '${g;p;}' /etc/resolv.conf 2>/dev/null) _hn=$(hostname) _hn=${_hn%%.*} sed -i -e "s/^127\.0\.0\.1.*/127.0.0.1\t${_hn}.${_dn:-$(get_fqdn my.domain)} ${_hn} localhost.localdomain localhost/" /etc/hosts setup-ntp ${NTPOPTS} setup-apkrepos ${APKREPOSOPTS} yes | setup-disk -q ${DISKOPTS} poweroff

The next one creates an answer file and runs setup-alpine. Note that sshd and network interface setup are included this time, even though they are both already up. It seems to work but not without complaint. More experimentation is required.

Contents of unattended.sh

cat <<-EOF > /root/answerfile KEYMAPOPTS="us us" HOSTNAMEOPTS="-n alpine-test" TIMEZONEOPTS="-z UTC" PROXYOPTS="none" NTPOPTS="-c busybox" APKREPOSOPTS="-r" SSHDOPTS="-c openssh" DISKOPTS="-m sys /dev/vda" INTERFACESOPTS="auto lo iface lo inet loopback auto eth0 iface eth0 inet dhcp " empty_root_password="true" EOF yes | setup-alpine -f /root/answerfile

The third is like the second except without the separate answer file and using cat to set the INTERFACEOPTS variable based on the interface currently in use.

Contents of unattended.sh

set -a KEYMAPOPTS="us us" HOSTNAMEOPTS="-n alpine-test" TIMEZONEOPTS="-z UTC" PROXYOPTS="none" NTPOPTS="-c busybox" APKREPOSOPTS="-r" SSHDOPTS="-c openssh" DISKOPTS="-m sys /dev/mmcblk0" #INTERFACESOPTS="auto lo #iface lo inet loopback # #auto eth0 #iface eth0 inet dhcp #" INTERFACESOPTS=$(cat /etc/network/interfaces) empty_root_password="true" yes | setup-alpine

The above scripts need to be improved, tested, and tailored for your own use. Edits welcome!

Overlay File Reference

The headless.apkovl.tar.gz file has the following structure:

└── etc ├── .default_boot_services ├── local.d │ └── headless.start └── runlevels └── default └── local -> /etc/init.d/local

Contents of headless.start

#!/bin/sh __clean_up() { rc-update del local rm /etc/local.d/headless.start } __config_net() { if [ ${ssid} ] then for dev in /sys/class/net/* do if [ -e "${dev}"/wireless -o -e "${dev}"/phy80211 ] then iface="${dev##*/}" fi done apk add wpa_supplicant cat <<-EOF > /etc/wpa_supplicant/wpa_supplicant.conf ap_scan=1 autoscan=periodic:10 disable_scan_offload=1 network={ ssid="${ssid}" psk="${psk}" } EOF rc-service wpa_supplicant start else iface="eth0" fi cat <<-EOF > /etc/network/interfaces auto lo iface lo inet loopback auto ${iface} iface ${iface} inet dhcp EOF rc-service networking start } __enable_ssh() { setup-sshd -c openssh cp /etc/ssh/sshd_config /etc/ssh/sshd_config.orig echo "PermitEmptyPasswords yes" >> /etc/ssh/sshd_config echo "PermitRootLogin yes" >> /etc/ssh/sshd_config rc-service sshd restart mv /etc/ssh/sshd_config.orig /etc/ssh/sshd_config } __login_root() { cat <<-EOF > /root/.profile rm -f /root/.profile if [ -e ${ovlpath}/unattended.sh ] && [ \$(tty) = /dev/tty7 ] then source ${ovlpath}/unattended.sh fi EOF openvt -s -c 7 -- /bin/login -f root } ovlpath=$(find /media -name *.apkovl.tar.gz -exec dirname {} \;) read ssid psk < "${ovlpath}/wifi.txt" __config_net __enable_ssh __clean_up __login_root