Proxmox: OpenCTI in a Linux Container (LXC)

In this post, I walk you through steps of running an OpenCTI server in an unprivileged Linux Container in Proxmox to aggregate threat intelligence into a single interface.
Proxmox: OpenCTI in a Linux Container (LXC)
In: Proxmox, Home Lab, Defend, Threat Hunting, Threat Intel, OpenCTI

OpenCTI Project Links

System Requirements


Increase the virtual memory that can be allocated by processes, as Elasticsearch will require a higher amount than is the default value. Since the Linux Container uses the host's kernel, these values will be inherited.

sysctl -w vm.max_map_count=262144
sysctl -p
echo -e '\n# Increase virtual memory (e.g. Elasticsearch)' >> /etc/sysctl.conf
echo 'vm.max_map_count=262144' >> /etc/sysctl.conf

Run the pveversion command to ensure that your Proxmox environment conforms to that shown just below:

pve-manager/8.1.3/b46aac3b42da5d15 (running kernel: 6.5.11-7-pve)

Reference my guide on installing Docker on Linux Containers in Proxmox.

Proxmox: Run Docker on Linux Containers (LXC)
In this post, I show you how to run Docker in your Linux Containers (LXC), allowing you to save on resource requirements typically required by a VM.


Note that these are the recommended system specifications:
CPU RAM Disk Space
6 Cores 16GiB >32GB

I'll be running my Linux Container with:

Monitor the performance of your OpenCTI container after you deploy the entire tech stack with some connectors. You may be able to decrease the CPU and RAM values to save resources, but this will depend greatly on the number of connectors you have running concurrently.
  • 8 Cores
  • 16 GiB RAM
  • 128 GB disk

Creating the Container


Note that the network values are specific to my environment! Change accordingly.
Do not start the container yet!

Updating some Options

Adding Additional Features

  1. Click your container
  2. Go to the Options menu
  3. Double-click on Features and ensure yours matches

Allow the Container to Increase Memory

For more information, see here: and reference RLIMIT_MEMLOCK

Since we are running these docker images in an unpriviliged Linux Container, we have to allow the LXC to increase memory as needed to run elasticsearch.

  1. Open a shell on the PVE node
  2. Execute the following commands
echo 'lxc.prlimit.memlock: unlimited' >> "/etc/pve/lxc/$container_id.conf"
Any time you take a snapshot, you will need to append this line to the bottom of the snapshot, so that it will rollback with these configurations intact anytime you restore said snapshot.

Installing OpenCTI

  1. Start your Linux Container
  2. SSH or open a terminal via some other means on the host
  3. Follow along with the instructions below

The official documentation states that Docker is the recommended method to run the OpenCTI components, so that's what we'll be doing in this write-up.

Install Docker Engine

If you haven't yet, follow along with my guide to install Docker Engine on your Linux Container.

Proxmox: Run Docker on Linux Containers (LXC)
In this post, I show you how to run Docker in your Linux Containers (LXC), allowing you to save on resource requirements typically required by a VM.

Install OpenCTI Stack

Create a Non-Root User

apt install -y sudo
useradd -r -s /bin/bash -m -d /opt/opencti -G sudo,docker opencti_svc
passwd opencti_svc

Log in as Non-Root User

Docker Compose File

When logging in as the opencti_svc user, you should be operating in /opt/opencti as the home directory. The first thing we'll do is grab the docker-compose.yml contents from this GitHub repository.

docker/docker-compose.yml at master · OpenCTI-Platform/docker
OpenCTI Docker deployment helpers. Contribute to OpenCTI-Platform/docker development by creating an account on GitHub.
wget -O docker-compose.yml
I prefer to serve OpenCTI over TCP/80, as opposed to TCP/8080 in the default installation. If you'd like to change it as well, follow along or skip to the next part.
nano docker-compose.yml

Environment Variables

Generate some environment variables by running this command:

cat << EOF > .env
CONNECTOR_EXPORT_FILE_CSV_ID=$(cat /proc/sys/kernel/random/uuid)
CONNECTOR_EXPORT_FILE_STIX_ID=$(cat /proc/sys/kernel/random/uuid)
CONNECTOR_HISTORY_ID=$(cat /proc/sys/kernel/random/uuid)
CONNECTOR_IMPORT_FILE_STIX_ID=$(cat /proc/sys/kernel/random/uuid)
CONNECTOR_IMPORT_REPORT_ID=$(cat /proc/sys/kernel/random/uuid)
MINIO_ROOT_PASSWORD=$(cat /proc/sys/kernel/random/uuid)
MINIO_ROOT_USER=$(cat /proc/sys/kernel/random/uuid)
OPENCTI_ADMIN_TOKEN=$(cat /proc/sys/kernel/random/uuid)

At this point you should have the following files in /opt/opencti

  • docker-compose.yml
  • .env
Some variables are just placeholders and need to be changed. Please update the variables shown below.
nano .env
    • Used to log into OpenCTI
    • Also, used for system and other alerts
    • Password to log into OpenCTI
    • Change this and store in a password vault
    • Change localhost to your FQDN or IP address
    • Example: or http://opencti.home.lab
    • Change this and store in a password vault
    • Change this and store in a password vault

Launch the OpenCTI Stack

At your initial deployment of the stack -- and with any subsequent updates to the stack -- you may need to wait a several minutes for all of the Docker components to initialize.

If the OpenCTI interface is not immediately available, be patient.
docker-compose up -d

To monitor any docker container logs after the stack is fully deployed, run the command docker-compose logs -f.

Logging into OpenCTI

In your web browser, navigate to http://ipaddress or http://fqdn. Remember, we configured the application to be served over TCP port 80, whereas most documentation references TCP port 8080.

The username and password were set by you in the .env variables file in OPENCTI_ADMIN_EMAIL and OPENCTI_ADMIN_PASSWORD respectively.

Upon first glance, the empty canvas on the OpenCTI UI can be a little underwhelming. OpenCTI does not ship with any data, so you either have to import it manually or use connectors to programmatically pull data.

Configuring OpenCTI Connectors

A list of officially supported connectors (and their configurations) is available on their GitHub repo.

GitHub - OpenCTI-Platform/connectors: OpenCTI Connectors
OpenCTI Connectors. Contribute to OpenCTI-Platform/connectors development by creating an account on GitHub.

Connectors are divided into several categories:

External ImportInternal EnrichmentInternal Export FileInternal Import FileStream

Configure an External Import Connector

AlienVault OTX

For the sake of this walkthrough, let's configure the AlienVault OTX external connector, since this is a very powerful and widely used threat intel exchange.

Connector Roles and Permissions

According to the official documentation, the proper way to add connectors to OpenCTI is:

Create a specific role for connectorsCreate an account per connector and attach the role to it

Click 'Settings' in the bottom-left

Create the Connector Account

We're still working in the Accesses tab from above.

Click the 'Users' tab
Click the 'Create a user' button
Fill out the details of the user

Specify a password for the connector account and click Create.

Update the Account Roles

Click on the account name
While you're here, make a note of the API token

Click anywhere outside of the pane to return to the main view.

Update the Docker-Compose Configuration

We are going to use the docker-compose.yml template for the AlienVault connector directly from the project GitHub. We'll be borrowing a portion of this file and injecting into the main docker-compose.yml.

connectors/docker-compose.yml at master · OpenCTI-Platform/connectors
OpenCTI Connectors. Contribute to OpenCTI-Platform/connectors development by creating an account on GitHub.
Indentation is very important for YAML, so please be sure to maintain the indentation when pasting into your docker-compose.yml file.

I'm going to copy and paste only the text highlighted in the screenshot:

I like to put the connector configurations at the top, since it's easier to find them there.
cd /opt/opencti
nano docker-compose.yml

The screenshot below indicates how I copied and pasted the YAML syntax right above the redis and below the services keywords in the original file. I've also appended the following YAML syntax to the connector:

      - opencti

This causes Docker Compose to pause initialization of the connector until the opencti container has been brought up. Add this to all of your connector YAML syntax.

Before you save the changes to the file, we need to make some changes.
      - OPENCTI_TOKEN=ChangeMe


      - OPENCTI_TOKEN=connector-api-token-here

After: paste your API token for the AlienVault user here

      - CONNECTOR_ID=ChangeMe


Every connector must have a unique CONNECTOR_ID. There are UUID4 random generators on the web that you can use. Or, you can generate them in PowerShell or bash.

Bash: echo $(cat /proc/sys/kernel/random/uuid)

PowerShell: [Guid]::NewGuid().Guid

Then paste the output into the CONNECTOR_ID variable.

      - CONNECTOR_ID=random-uuid-v4-here




      - ALIENVAULT_API_KEY=alienvault-otx-api-key

After: log into your AlienVault account and retrieve this

You can now save the changes to your docker-compose.yml file. Once you've done that, you'll need to restart the OpenCTI stack by issuing these commands.

cd /opt/opencti
docker-compose down && docker-compose up -d

Again, you can watch the Docker container logs by running:

docker-compose logs -f
It can take a few minutes for everything to fully initialize after stack updates. Please be patient before panicking, because your OpenCTI web interface isn't coming up.

Exploring the Platform

In this tutorial, we got the platform installed and configured with a single external connector, the AlienVault connector. That is only scratching the surface in terms of available connectors and information you can import to the platform. Some other recommended external connectors to check out:

  • abuse-ssl
  • abuseipdb-ipblacklist
  • cve
  • mitre
  • opencti (yes, that is the name of the connector)
  • urlhaus

That is just to name a few. Remember the process generally follows these steps:

  1. Take the docker-compose.yml contents from the connector on GitHub
  2. Plug them into /opt/opencti/docker-compose.yml while being sure to maintain the indentation.
Please note that some connectors may require additional information such as API keys.
The walkthrough video below shows an OpenCTI environment that has been configured with information from various sources. So, please don't be surprised if your environment doesn't compare, as we have just gotten started.

Upgrading OpenCTI

Make a Snapshot of Your Container

Log into Proxmox and click on your OpenCTI Linux Container. Click on Snapshots > Take Snapshot. You could name it something like pre_upgrade_YYYYMMdd. You should see TASK OK in the output when the snapshot has been successfully created.

Update the OpenCTI Stack

cd /opt/opencti
docker-compose down && docker-compose pull && docker-compose up -d

Serving OpenCTI over TLS

Stop the OpenCTI Stack

cd /opt/opencti
docker-compose down

Create a Local Volume to Store TLS Cert and Key

nano docker-compose.yml

Append the 'opencti_https' volume to the list

    image: opencti/platform:5.12.15
      # ...
      # Removed by author for brevity
      # ...
      - "80:8080"
      - opencti_https:/certs
    # ...
      # ...

Run these chained commands to start the stack and create the volume, then shut it down, so we can add our certificates there.

docker-compose up -d && docker-compose down

This will create the following path /var/lib/docker/volumes/opencti_opencti_https/_data/. Once created, place your .crt and .key TLS files in this directory, which will require root privileges.

Update the OpenCTI Stack

Update the Environment Variables

This is just an example TLS configuration. Use the correct domain name for your environment.

Let's say you got a TLS certificate for your OpenCTI instance with the hostname, opencti.domain.tld. This is the hostname we'll be referencing throughout this configuration example.

cd /opt/opencti
nano .env




Save your changes.

Update Docker Compose

Let's use sed to easily update the OPENCTI_URL variable in the docker-compose.yml file. The command below, will do the following.

  • Backup the original docker-compose.yml to docker-compose.yml.bak
  • Update the OPENCTI_URL variable with your https://opencti.domain.tld URL
Be sure change opencti.domain.tld according to your domain!
sed -i.bak -e 's/OPENCTI_URL=http:\/\/opencti\:8080/OPENCTI_URL=https:\/\/opencti\.domain\.tld/g' docker-compose.yml

Change 'opencti\.domain\.tld' accordingly

nano docker-compose.yml
This assumes that you've saved your certificate files in /var/lib/docker/volumes/opencti_opencti_https/_data/ as opencti.key and opencti.crt respectively.
    image: opencti/platform:5.12.15
      # ...
      # ...
      # ...
      - APP__HTTPS_CERT__KEY=/certs/opencti.key
      - APP__HTTPS_CERT__CRT=/certs/opencti.crt
      - "443:8080"

Change '80:8080' to '443:8080'

Effectively, what we're doing is this:

  • Map /var/lib/docker/volumes/opencti_opencti_https/_data/opencti.key to /certs/opencti.key internally to the container
  • Map /var/lib/docker/volumes/opencti_opencti_https/_data/opencti.crt to /certs/opencti.crt internally to the container
  • Listen on TCP/443 — the default port for HTTP over TLS
  • Uncomment APP__HTTPS_CERT__REJECT_UNAUTHORIZED if you're testing with a self-signed certificate that does not have a valid CA.

Bring up the Stack

docker-compose up -d

Once you've made all of the designated changes to the stack, it's time to update the stack with your changes. Pressing this button will redploy the entire stack, so be patient while all of the changes are loaded and your containers are deployed.

Verify HTTPS Functionality

In your browser, try navigating to your new URL, https://opencti.domain.tld. You should find that your site loads normally and that your browser trusts the connection as evidenced by the padlock icon in the URL bar.

Also, make sure your containers are not reporting any issues with connecting to the API.

docker-compose logs -f

Inspect your worker and connector logs and ensure there are no error logs regarding API connectivity issues.


If you've followed along up to this point, I want to thank you for reading. I hope that this blog has helped you successfully get your OpenCTI instance running inside of an unprivileged Linux Container in Proxmox.

OpenCTI is a powerful cyber threat intelligence engine that can aggregate and enhance data from multiple sources. Check out their documentation for more ways to enhance your OpenCTI instance.

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