anchor.diff:    };
   
     config = {
  -    system.activationScripts = {
  -      inherit ec2-autohostname;
  -    };
  -
       systemd.services.ec2-autohostname = {
         description = "EC2: apply dynamic hostname";
   
  -      wantedBy = [ "multi-user.target" "sshd.service" ];
  -      before = [ "sshd.service" ];
         after = [ "fetch-ec2-data.service" ];
   
         script = ec2-autohostname;
   
         serviceConfig.Type = "oneshot";
         serviceConfig.RemainAfterExit = true;
  +      unitConfig.X-StopOnReconfiguration = true;
       };
     };
   }
  
positive.code:     hostname=$(${hostname}).${zone}
      record_value=$(${wget} http://169.254.169.254/latest/meta-data/${query})
  
      ${retry} ${curl-nofail} -d @/dev/stdin \
            -H "Content-Type: text/xml" \
            -H "x-amz-date: $date" \
            -H "$auth_header" \
  
negative.code:   bash = "${pkgs.bash}/bin/bash";
    xargs = "${pkgs.findutils}/bin/xargs";
  
    retry-wrapper = script: pkgs.writeScript "retry-${script.name}" ''
      ${retry} ${script}
    '';
  
    register-hostname = {
      zoneId, zone, iamCredentialName,
      useLocalHostname,
      query ? if useLocalHostname then "local-ipv4" else "public-hostname",
      recordType ? if useLocalHostname then "A" else "CNAME"
    }: pkgs.writeScript "ec2-register-hostname-${zone}" ''
      #!${bash}
      date=$(${curl} -I https://route53.amazonaws.com/date | ${awk} '/^Date: / {sub("Date: ", "", $0); sub("\\r", "", $0); print $0}')
  
      iam="${iamCredentialName}"
  