diff --git a/gpu_detector.yml b/gpu_detector.yml
new file mode 100644
index 0000000..502024c
--- /dev/null
+++ b/gpu_detector.yml
@@ -0,0 +1,5 @@
+---
+- hosts: scheduler
+  become: true
+  roles:
+    - gpu_detector
diff --git a/roles/gpu_detector/files/warn_gpu_not_used b/roles/gpu_detector/files/warn_gpu_not_used
new file mode 100755
index 0000000..e6ba0a9
--- /dev/null
+++ b/roles/gpu_detector/files/warn_gpu_not_used
@@ -0,0 +1,242 @@
+#!/bin/env python3
+
+from collections import namedtuple
+import datetime
+import json
+import os
+import pynumparser
+import re
+import requests
+import smtplib
+import subprocess
+import time
+
+EMAIL_MESSAGE = """
+Dear Peregrine user.
+
+A script detected that one of your jobs on peregrine in the GPU queue is not using the GPU.
+
+If they should be using the GPU could you please look into your code?
+If you need help with that, we can recommend the walk in sessions of the support team.
+https://wiki.hpc.rug.nl/peregrine/additional_information/walk-in_sessions
+
+If the jobs are not supposed to use the gpu, please submit them to one of the other queues.
+
+Yours sincerely,
+
+Team HPC
+
+ps: The following job was canceled:
+
+"""
+
+
+def line_to_job(line):
+    """
+    Convert a sring containing <job-id>,<h-mm:ss>
+    to a named tuple, containing id and seconds.
+
+    Args:
+        line (string): line from squeue
+    Returns:
+        Job or None
+    """
+    Job = namedtuple('Job', ['id', 'delta', 'node', 'user'])
+    params = line.split(',')
+    timestring = params[1]
+    if '-' in timestring:
+        days, remainder = timestring.split('-')
+        days = int(days)
+    else:
+        days = 0
+        remainder = timestring
+
+    values = [0, 0, 0] + [int(i) for i in remainder.split(':')]
+    hours, minutes, seconds = values[-3:]
+
+    delta = datetime.timedelta(
+        days=days, hours=hours, minutes=minutes, seconds=seconds)
+    params[1] = delta
+    try:
+        return Job(*params)
+    except:
+        return None
+
+
+def parse_gpu_string(node_string):
+    """
+    Parses a string in the format of.
+    pg-gpu[1-3] or pg-gpu[2,4,5]
+
+    Args:
+      node_string (string): The GPU node(s) in slurm format.
+      end (int): end of measurements timestamp.
+    Returns: list: A list of hostnames.
+    """
+    match = re.search('(.+\[)([0-9]|-|,)+?(?=\])', node_string)
+    if match is None:
+        return [node_string]
+
+    base, sequence = match.group().split('[')
+    parser = pynumparser.NumberSequence(int)
+    return ['{}{:02d}'.format(base, i) for i in parser.parse(sequence)]
+
+
+def get_gpus_usage(nodes, start, end):
+    """
+    Calculate the average GPU usage between begin and end stamps.
+    of a sequence of gpus.
+    Args:
+        nodes (list): The GPU node(s) in slurm format.
+        start (int): start of measurements timestamp.
+        end (int): end of measurements timestamp.
+    Returns:
+        list: A list of tuples [(<hostname>, <percentage>)]
+    """
+    usages = [(gpu, get_gpu_usage(gpu, start, end)) for gpu in parse_gpu_string(nodes)]
+    return usages
+
+def get_gpu_usage(node, start, end):
+    """
+    Calculate the average GPU usage between begin and end stamps.
+    Args:
+        node (string): The GPU node
+        start (int): start of measurements timestamp.
+        end (int): end of measurements timestamp.
+    Returns:
+        float: The average usage (%)
+    """
+    payload = {
+        'query':
+        'utilization_gpu{{env="peregrine",instance="{}:9101",job="gpu"}}'.
+        format(node),
+        'start':
+        start,
+        'end':
+        end,
+        'step':
+        '60s'
+    }
+    try:
+        data = requests.get(
+            'https://knyft.hpc.rug.nl:9091/api/v1/query_range', params=payload)
+
+        values = json.loads(data.content.decode())['data']['result'][0]['values']
+        average = sum([int(i[1]) for i in values]) / len(values)
+    except:
+        import ipdb; ipdb.set_trace()
+
+    return average
+
+
+def gpu_load(job):
+    """
+    Calculate the GPU load of a RUNNING job.
+    Args:
+        job (Job)
+    Returns:
+        list: A list of tuples [(<hostname>, <percentage>)]
+
+    """
+    end = time.time()
+    start = end - job.delta.total_seconds()
+    return get_gpus_usage(job.node, start, end)
+
+
+def post_to_slack(message: str, slack_url: str):
+    """
+    Post a message to slack.
+
+    Args:
+        message (str): Message to post
+        slack_url (str): url to post message to
+    """
+    data = json.dumps({
+        'channel': '#peregrine-alerts',
+        'username': 'kill-hogs',
+        'text': message,
+        'icon_emoji': ':scales:'
+    }).encode('utf-8')
+    response = requests.post(
+        slack_url, data=data, headers={'Content-Type': 'application/json'})
+
+
+def find_email(username):
+    """
+    Return the email adress of <username> as reported by finger.
+
+    Args:
+      username (string): the username of the account.
+
+    Returns:
+      string: email adress or None
+
+    """
+    finger = subprocess.run(
+        'finger {} -l -m'.format(username),
+        shell=True,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE)
+    try:
+        data = finger.stdout.decode("utf-8").split('\n')
+        # Basic check: exactly one `@` and at least one `.` after the `@`.
+        match = re.search(r'(?<=Name: )[^@]+@[^@]+\.[^@]+$', data[0])
+        return match.group(0)
+
+    except IndexError:
+        # a more explicit pass
+        return None
+
+
+def send_mail(sender: str, receiver: str, message: str, port: int = 25):
+    """
+    Send a message to a user whose processes have been killed.
+    """
+
+    message = f"""From: "(Kill Hogs)" <{sender}>
+To: <{receiver}>
+Subject: GPU job canceled.
+
+{message}
+    """
+
+    try:
+        smtpObj = smtplib.SMTP('localhost', port=port)
+        smtpObj.sendmail(sender, [receiver], message)
+        print(f"Successfully sent email to {receiver}.")
+    except Exception as e:
+        print("Error: unable to send email.\nThe error was:\n{}".format(e))
+
+
+def main():
+    jobs = subprocess.check_output([
+        'squeue', '--partition', 'gpu', '--state=R', '-h', '-o', '%i,%M,%N,%u'
+    ])
+    jobs = [line_to_job(l) for l in jobs.decode().split('\n') if l != '']
+    jobs = list(filter(lambda a: a != None, jobs))
+    long_jobs = filter(lambda j: j.delta.total_seconds() > 3600, jobs)
+    message = []
+    for job in long_jobs:
+        gpus_usage = gpu_load(job)
+        for entry in gpus_usage:
+            gpu, usage = entry
+            job_info = f'Job id:  {job.id:10}  User: {job.user:9} Gpu usage: {usage:5.1f} ({gpu})'
+            print(job_info)
+
+            if usage == 0.0:
+                message.append(job_info)
+                subprocess.check_output(['scancel', str(job.id)])
+                send_mail(
+                    sender='root@peregrine.hpc.rug.nl',
+                    receiver=find_email(job.user),
+                    message=EMAIL_MESSAGE + job_info)
+
+    slack_url = os.environ.get('SLACK_URL')
+    if message != [] and slack_url is not None:
+        message = ['The following jobs are canceled:'] + message
+        post_to_slack(message='\n'.join(message), slack_url=slack_url)
+        print(message)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/roles/gpu_detector/tasks/main.yml b/roles/gpu_detector/tasks/main.yml
new file mode 100644
index 0000000..e6b6401
--- /dev/null
+++ b/roles/gpu_detector/tasks/main.yml
@@ -0,0 +1,27 @@
+---
+- name: Install yum dependencies
+  yum:
+    state: latest
+    update_cache: yes
+    disable_gpg_check: yes
+    name:
+      - python3-pynumparser
+
+- name: install the script.
+  copy:
+    src: files/warn_gpu_not_used
+    dest: /sbin/warn_gpu_not_used
+    mode: 0755
+
+- cron:
+    name: Cancel gpu jobs not using any gpu.
+    minute: '*/15'
+    user: root
+    job: 'SLACK_URL={{ slack_url }} /usr/bin/python3 /sbin/warn_gpu_not_used'
+    cron_file: warn_gpu_not_used
+
+# Don't buzz the whole team... yet
+- cronvar:
+    name: MAILTO
+    value: e.m.a.rijpkema@rug.nl
+    cron_file: warn_gpu_not_used
diff --git a/roles/gpu_detector/vars/main.yml b/roles/gpu_detector/vars/main.yml
new file mode 100644
index 0000000..c48c2c7
--- /dev/null
+++ b/roles/gpu_detector/vars/main.yml
@@ -0,0 +1,10 @@
+$ANSIBLE_VAULT;1.1;AES256
+64653062613335636139663930383861366163626366393034383436663264626266326138353461
+3236633634366335663530643934333634376264663330660a356161333937356464353635363165
+31613530313765373435383334393335666632666661636538393361303862663562383832383565
+3962363636663437620a633039343431623138376162656336396666316530376466633363323734
+33373137336233346261636366343264316636623732313965616535356366633139313939343966
+34386366323863396162366630353537353061306233313531663236613131346334376432346535
+30613937356565396131373462323762363935343764373264666661313065626538643832663435
+39303931656166646362386636373466323333313363323234323866333662373830363365616663
+3236