docker/dtr emergency-repair

Estimated reading time: 3 minutes

This topic applies to Docker Enterprise.

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Recover DTR from loss of quorum


docker run -it --rm docker/dtr \
    emergency-repair [command options]


This command repairs a DTR cluster that has lost quorum by reverting your cluster to a single DTR replica.

There are three steps you can take to recover an unhealthy DTR cluster:

  1. If the majority of replicas are healthy, remove the unhealthy nodes from the cluster, and join new ones for high availability.
  2. If the majority of replicas are unhealthy, use this command to revert your cluster to a single DTR replica.
  3. If you can’t repair your cluster to a single replica, you’ll have to restore from an existing backup, using the restore command.

When you run this command, a DTR replica of your choice is repaired and turned into the only replica in the whole DTR cluster. The containers for all the other DTR replicas are stopped and removed. When using the force option, the volumes for these replicas are also deleted.

After repairing the cluster, you should use the join command to add more DTR replicas for high availability.


Option Environment Variable Description
--debug $DEBUG Enable debug mode for additional logs.
--existing-replica-id $DTR_REPLICA_ID The ID of an existing DTR replica. To add, remove or modify DTR, you must connect to an existing healthy replica’s database.
--help-extended $DTR_EXTENDED_HELP Display extended help text for a given command.
--overlay-subnet $DTR_OVERLAY_SUBNET The subnet used by the dtr-ol overlay network. Example: For high-availability, DTR creates an overlay network between UCP nodes. This flag allows you to choose the subnet for that network. Make sure the subnet you choose is not used on any machine where DTR replicas are deployed.
--prune $PRUNE Delete the data volumes of all unhealthy replicas. With this option, the volume of the DTR replica you’re restoring is preserved but the volumes for all other replicas are deleted. This has the same result as completely uninstalling DTR from those replicas.
--ucp-ca $UCP_CA Use a PEM-encoded TLS CA certificate for UCP. Download the UCP TLS CA certificate from https:// /ca, and use `--ucp-ca "$(cat ca.pem)"`.
--ucp-insecure-tls $UCP_INSECURE_TLS Disable TLS verification for UCP. The installation uses TLS but always trusts the TLS certificate used by UCP, which can lead to MITM (man-in-the-middle) attacks. For production deployments, use --ucp-ca "$(cat ca.pem)" instead.
--ucp-password $UCP_PASSWORD The UCP administrator password.
--ucp-url $UCP_URL The UCP URL including domain and port.
--ucp-username $UCP_USERNAME The UCP administrator username.
--y, yes $YES Answer yes to any prompts.
dtr, cli, emergency-repair