Running OpenSearch in Rootless Podman Containers#

Modern infrastructure demands robust security practices, and running containers with reduced privileges is a key component of defense-in-depth strategies. This guide demonstrates how to run OpenSearch in rootless Podman containers with proper systemd integration, enabling powerful search capabilities without requiring root privileges.

Why Rootless Containers?#

Rootless containers provide several security benefits:

Reduced attack surface - compromised containers can’t easily escalate to root privileges
User namespace isolation - containers run with regular user privileges
Improved security posture - follows the principle of least privilege
Regulatory compliance - helps meet security requirements in regulated environments

Prerequisites#

Before starting, ensure you have:

Linux system with Podman 3.0+ installed
systemd user service support
At least 2GB of available RAM (4GB+ recommended for production)
Appropriate kernel settings (covered below)

Step 1: System Preparation#

First, we’ll configure the necessary kernel parameters to allow for ElasticSearch-like applications in rootless containers:

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# Create a sysctl configuration file
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cat << EOF | sudo tee /etc/sysctl.d/99-opensearch.conf
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vm.max_map_count=262144
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fs.file-max=65536
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EOF
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# Apply the settings
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sudo sysctl --system

Step 2: Create Data Directory#

Create a persistent storage location for OpenSearch data:

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mkdir -p ~/.local/share/opensearch-data
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chmod 700 ~/.local/share/opensearch-data

Step 3: Create systemd Service File#

Create a systemd user service file to manage the OpenSearch container:

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mkdir -p ~/.config/systemd/user/
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cat << EOF > ~/.config/systemd/user/container-opensearch-node1.service
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[Unit]
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Description=Podman container-opensearch-node1.service
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Documentation=man:podman-generate-systemd(1)
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Wants=network-online.target
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After=network-online.target
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RequiresMountsFor=%t/containers
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[Service]
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Environment=PODMAN_SYSTEMD_UNIT=%n
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Restart=on-failure
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TimeoutStopSec=70
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ExecStartPre=/bin/rm -f %t/%n.ctr-id
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ExecStart=/usr/bin/podman run \\
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    --cidfile=%t/%n.ctr-id \\
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    --cgroups=no-conmon \\
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    --rm \\
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    --sdnotify=conmon \\
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    --replace \\
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    -d \\
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    --name opensearch-node1 \\
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    -e cluster.name=opensearch-cluster \\
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    -e node.name=opensearch-node1 \\
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    -e discovery.type=single-node \\
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    -e "OPENSEARCH_JAVA_OPTS=-Xms512m -Xmx512m" \\
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    -e OPENSEARCH_INITIAL_ADMIN_PASSWORD=Anubhav@321 \\
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    -e DISABLE_INSTALL_DEMO_CONFIG=false \\
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    -e DISABLE_SECURITY_PLUGIN=false \\
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    -e bootstrap.memory_lock=false \\
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    --ulimit nofile=65536:65536 \\
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    -v $HOME/.local/share/opensearch-data:/usr/share/opensearch/data:Z,rw \\
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    -p 9200:9200 \\
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    -p 9600:9600 \\
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    --user $(id -u):$(id -g) \\
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    docker.io/opensearchproject/opensearch:latest
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ExecStop=/usr/bin/podman stop --ignore --cidfile=%t/%n.ctr-id
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ExecStopPost=/usr/bin/podman rm -f --ignore --cidfile=%t/%n.ctr-id
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Type=notify
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NotifyAccess=all
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[Install]
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WantedBy=default.target
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EOF

Step 4: Enable and Start the Service#

Now let’s enable and start our OpenSearch service:

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# Reload systemd configuration
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systemctl --user daemon-reload
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# Enable the service to start at login
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systemctl --user enable container-opensearch-node1.service
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# Start the service
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systemctl --user start container-opensearch-node1.service
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# Enable lingering to allow the service to run without being logged in
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loginctl enable-linger $(whoami)

Step 5: Verify the Deployment#

After giving OpenSearch about 30-45 seconds to initialize, verify that it’s running correctly:

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# Check service status
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systemctl --user status container-opensearch-node1.service
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# Test HTTPS endpoint with admin credentials
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curl -k -u admin:Anubhav@321 https://localhost:9200/_cluster/health

You should see output similar to:

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{
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  "cluster_name": "opensearch-cluster",
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  "status": "green",
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  "timed_out": false,
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  "number_of_nodes": 1,
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  "number_of_data_nodes": 1,
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  "discovered_master": true,
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  "active_primary_shards": 1,
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  "active_shards": 1,
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  "relocating_shards": 0,
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  "initializing_shards": 0,
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  "unassigned_shards": 0,
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  "delayed_unassigned_shards": 0,
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  "number_of_pending_tasks": 0,
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  "number_of_in_flight_fetch": 0,
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  "task_max_waiting_in_queue_millis": 0,
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  "active_shards_percent_as_number": 100.0
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}

Understanding the systemd Service Configuration#

Let’s break down the key parts of our service file: