How to run Slicer as a Daemon

The term "daemon" is a well established phrase from UNIX meaning a process that runs in the background. Daemons are usually managed by an init system which can monitor and restart them.

Not only can we monitor Slicer's logs via journalctl, but we can manage it with standard systemctl commands.

Let's take the example from the walkthrough and create a systemd service for it:

Create a service named i.e. vm-image.service:

[Unit]
Description=Slicer

[Service]
User=root
Type=simple
WorkingDirectory=/home/alex
ExecStart=sudo -E /usr/local/bin/slicer up \
  /home/alex/vm-image.yaml \
  --license-file /home/alex/.slicer/LICENSE
Restart=always
RestartSec=30s
KillMode=mixed
TimeoutStopSec=30

[Install]
WantedBy=multi-user.target

Install the service, and set it to start up on reboots:

sudo cp ./vm-image.service /etc/systemd/system/
sudo systemctl enable vm-image.service

Now before starting the service, make sure you shut down any existing Slicer process that is managing this particular VM.

Then:

sudo systemctl start vm-image.service

To view the logs for the service run:

# Page through all logs
sudo journalctl --output=cat -u vm-image

# Tail the latest logs
sudo journalctl --output=cat -f -u vm-image

# View all logs since today/yesterday
sudo journalctl --output=cat --since today -u vm-image
sudo journalctl --output=cat --since yesterday -u vm-image

To stop the service run sudo systemctl stop vm-image, and to prevent it loading on start-up run: sudo systemctl disable vm-image.

You can create multiple Slicer services to run different sets of VMs or configurations on the same host.