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Flox and systemd

Flox environments have a built-in concept of services. Flox environment services are managed by invoking the flox services category of sub-commands such as flox services status.

This tutorial shows how to create and use systemd services with Flox by creating unit files manually. You will learn how to run a Flox environment service as both a systemd user unit and a systemd system unit.

Prerequisites

  • A Linux system with systemd support. This tutorial was tested on Ubuntu 24.04.
  • Flox installed in multi-user mode. This tutorial was tested on Flox 1.10.0.

Run a Flox environment service as a systemd user unit

In this section you will set up a Redis service from a FloxHub environment and run it as a systemd user unit.

Create the Redis environment locally

Create a directory for the environment and pull the flox/redis environment from FloxHub:

mkdir -p redis
cd redis

flox pull flox/redis

Test the environment with Flox services

Before creating the systemd unit, verify that the environment works with Flox services commands:

flox activate

flox services status
flox services start

redis-cli ping
# should respond PONG

Once verified, stop the services and exit the environment:

flox services stop
exit

Create the systemd user service

Note

The linger configuration is only required if you want the service to start on boot without a login. Otherwise the user must be logged in before the systemd service attempts to start.

Create the systemd user unit file:

cat > ~/.config/systemd/user/redis.service << 'EOF'
[Unit]
Description=Redis Server (Flox)

[Service]
ExecStart=flox activate -d /home/ubuntu/redis -- bash -c 'redis-server "$REDISCONFIG" --daemonize no --dir "$REDISDATA"'

[Install]
WantedBy=default.target
EOF

Note

Update the path /home/ubuntu/redis in the ExecStart line to match the location where you created the environment.

Enable lingering so the service starts at boot without login:

sudo loginctl enable-linger ubuntu

Load, enable, and start the service:

systemctl --user daemon-reload
systemctl --user enable redis.service
systemctl --user start redis.service

Verify the service is running:

systemctl --user status redis.service

Verify Redis is responding:

flox activate -d /home/ubuntu/redis -- redis-cli -p 16379 ping
# should respond PONG

Run a Flox environment service as a systemd system unit

For services that should run under a dedicated system user rather than your personal account, you can create a system-level systemd unit instead.

Create a dedicated Redis user

sudo useradd --system --no-create-home --shell /usr/sbin/nologin redis

Create the environment and set ownership

sudo mkdir -p /home/redis
sudo flox pull flox/redis -d /home/redis/redis
sudo chown -R redis:redis /home/redis

Create the system unit file

Since the redis user has no login session, user units will not work. Create a system unit instead:

sudo tee /etc/systemd/system/redis.service << 'EOF'
[Unit]
Description=Redis Server (Flox)

[Service]
User=redis
ExecStart=flox activate -d /home/redis/redis -- bash -c 'redis-server "$REDISCONFIG" --daemonize no --dir "$REDISDATA"'

[Install]
WantedBy=multi-user.target
EOF

Note

Enable lingering is not needed for system units. System units start at boot automatically.

Load, enable, and start

sudo systemctl daemon-reload
sudo systemctl enable redis.service
sudo systemctl start redis.service

Verify

sudo systemctl status redis.service

sudo flox activate -d /home/redis/redis -- redis-cli -p 16379 ping
# should respond PONG

Note

Key differences from the user unit approach: the system unit goes in /etc/systemd/system/, uses multi-user.target, requires sudo, and no lingering is needed.

Where to next?