DSS does not start / Cannot connect

When DSS fails to properly start, the following symptoms can happen:

  • dss start fails

  • dss status indicates that some processes are not started

  • “Could not connect to DSS server” banner when trying to connect using a browser (HTTP code: 502, type: Gateway error)

  • “Connection refused” error when trying to connect using a browser


If you are using the Dataiku virtual machine, please see The dedicated documentation for troubleshooting instructions.

Check processes state

The first step is to check the state of the DSS process:

  • Go to the DSS data directory

  • Run

    ./bin/dss status

If all processes are indicated as RUNNING, proceed to the next step

If a process is not in RUNNING state, first try to restart DSS:

./bin/dss restart

If it does not help, and some processes are still failing, see “Diagnose process failures” below.

If all processes are now RUNNING and you still get errors when connecting, proceed to the next step

Verify local connectivity

From the DSS machine, run


If you don’t see HTML code, and the nginx process is correctly running, you might have a local firewall issue

Then run:


If you don’t see a JSON result, check the status and logs of the backend process

If both of these tests are successful but you can’t connect from your browser, it indicates a network connectivity issue between DSS and your browser. Check for firewalls and proxies along the way. Try with another browser or another workstation if applicable.

DSS start (or stop) fails

It can happen that running ./bin/dss start fails

Server port already in use

Before starting, DSS checks that all TCP ports required are free. DSS requires up to 10 consecutive TCP ports, starting from the base port set at install time. Check that this whole range is available.

This error can also indicate that some stray DSS processes are still running, but are not controlled anymore by the DSS supervisor. See “Kill all DSS processes” below.

Server requires authentication

If you receive this message, it generally indicates that you ran the DSS installer or a dssadmin command while DSS was still running. It won’t be possible to stop DSS normally. See “Kill all DSS processes” below.

Kill all DSS processes

If some stray DSS processes are still running, you’ll need to kill them.

Run ps -u $USER -f to identify all processes running as the DSS service account, and use kill -9 PID to kill all DSS processes:

  • Java processes

  • Python processes

  • nginx processes

Diagnose process failures

check which process is failing, and check the run/PROCESS.log file, where PROCESS is the name of the failing process.

In particular, if the backend process is failing, check run/backend.log for errors.

Common issues that can prevent DSS from starting include:

  • Out of disk space (“No space left on device”) on the DSS data directory

  • Permissions issues (all files must belong to the DSS service account)

Also see Diagnosing and debugging issues and Obtaining support.