Is it possible to script starting up a FreeBSD VM, running a program in it, and fetching the result?

Question

I have a library that I'd like to test on FreeBSD. My CI setup doesn't have any FreeBSD systems, and adding them would be difficult, but I can spin up a VM inside my CI script. (In fact, I already do this to test on more exotic Linux kernel versions.)

For Linux, this is pretty easy: grab a pre-built machine image from some distro site, and use cloud-init to inject a first-run script, done.

Is it possible to do the same thing with FreeBSD? I'm looking for an automated way to take a standard FreeBSD machine image (e.g. downloaded from https://freebsd.org), boot it, and inject a program to run. The tricky part is that it should be entirely automated – I don't want to have to manually click through an installer ever time FreeBSD makes a new release.

Answer 1

Out of the box, there is no option like cloud-init but you could create your own image and use firstboot for example, this script is used to bootstrap a VM with saltstack in AWS:

#!/bin/sh

# KEYWORD: firstboot
# PROVIDE: set_hostname
# REQUIRE: NETWORKING
# BEFORE:  login

. /etc/rc.subr

name="set_hostname"
rcvar=set_hostname_enable
start_cmd="set_hostname_run"
stop_cmd=":"

export AWS_ACCESS_KEY_ID=key
export AWS_SECRET_ACCESS_KEY=secret
export AWS_DEFAULT_REGION=region

TAG_NAME="Salt"
INSTANCE_ID=$(/usr/local/bin/curl -s http://169.254.169.254/latest/meta-data/instance-id)
REGION=$(/usr/local/bin/curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone | sed 's/.$//')
TAG_VALUE=$(/usr/local/bin/aws ec2 describe-tags --filters "Name=resource-id,Values=${INSTANCE_ID}" "Name=key,Values=$TAG_NAME" --region ${REGION} --output=text | cut -f5)

set_hostname_run()
{
    hostname ${INSTANCE_ID}
    sysrc hostname="${INSTANCE_ID}"
    sysrc salt_minion_enable="YES"
    echo ${INSTANCE_ID} > /usr/local/etc/salt/minion_id
    pw usermod root -c "root on ${INSTANCE_ID}"
    if [ ! -z "${TAG_VALUE}" ]; then
        echo "node_type: ${TAG_VALUE}" > /usr/local/etc/salt/grains
    fi
    service salt_minion start
}

load_rc_config $name
run_rc_command "$1"

To create your own images you could use this script as a starting point: https://github.com/fabrik-red/images/blob/master/fabrik.sh#L124, more info here: https://fabrik.red/post/creating-the-image/

You can also simply install FreeBSD in Virtualbox, configure scripts related to firstboot, test and when you are happy with the results, export it, just be careful before exporting it that /firstboot exists (touch /firstboot) since after the first boot it will be removed and it could happen that after you export it if is not present it will not call the scripts.

After you have created the image you can use it multiple times, no need to create a new "custom" VM every time, it all depends on the scripts you use to bootstrap and load the scripts on the "firstboot".