create-dev-container.sh

containerName=dev
dir=/tmp/$containerName

if [[ $EUID != 0 ]]; then
   echo "This script must be run as root"
   exit 1
fi

nixos-container create $containerName

mkdir -p $dir
service=$dir/container@$containerName.service

cp /etc/systemd/system/container@.service $service
chmod a+w $service

mkdir -p /etc/systemd-mutable/system
ln -s $service /etc/systemd-mutable/system

# Copy the service scripts to $dir and replace the paths in $service with the copies
$(nix-build --no-out-link '<nixpkgs>' -A ruby)/bin/ruby - $service $dir <<'EOF'
require 'fileutils'

service, dir = ARGV
src = File.read(service)

['ExecStart', 'ExecStartPre', 'ExecStartPost', 'ExecStop'].each do |script|
  src = src.gsub(/^(#{script}=)(\S+)/) do |_|
    prefix = $1
    script_source = $2
    mutable_source = File.join(dir, script)
    FileUtils.cp(script_source, mutable_source)
    FileUtils.chmod('+w', mutable_source)
    "#{prefix}#{mutable_source}"
  end
end

File.write(service, src)
EOF

systemctl daemon-reload

echo "You can now edit these files to change the service"
printf '%s\n' $dir/*