Infrastructure Layer

Common errors with solutions

Gremlin Agent errors


There are several reasons an agent can lose communication to the control plane. Common examples include

  • Running a network based attack that affected the traffic. Ensure both and DNS are white-listed.
  • Running a CPU attack has starved Gremlin of the ability to compute API encryption. This is rare but it does happen.

In the event of a LostCommunication error, The Gremlin agent will trigger it's dead-man switch and cease all attacks.

This can occur on a host when running a network attack, when a previous network attack had been run AND the Gremlin agent was killed mid attack by the user, system or other tool which did not allow Gremlin to run garbage collection.

To solve, please run gremlin rollback.

Failed to parse execution attribute ‘pid’ for execution < HASH_STRING >

There are two non-exclusive modes of failure that can occur with this error message:

  • The running version of Gremlin is several versions out of date
    • Update the Gremlin agent or docker image
  • /var/lib/gremlin/executions has become corrupt
    • Delete the file /var/lib/gremlin/executions

Docker Errors

Non-zero exit code (137)

Docker has killed the container via kill -9. This is often attributed to OOM issues, and is most often seen when running a memory attack. Allocating more RAM to Docker usually solves the issue.

Non-zero exit code (1)

  • Unable to find local credentials file: Gremlin is not configured to point to the correct credentials file, usually located in /var/lib/gremlin. Ensure the credentials file(s), either certificates of API keys, exists and Gremlin has read+write access.

  • Permission denied (os error 13): The Gremlin container does not have proper filesystem permissions. Gremlin requires write access to /var/lib/gremlin, including the ability to create new files. Check permission on the host, and ensure write access is being passed through via docker when running the Gremlin container.

OS Error 1

This is often observed in the context of Capabilities: Unable to inherit one or more required capabilities: cap_net_admin, cap_net_raw

Solution: You'll need to add some capabilities to that docker container (full list here:

Example: docker run -it --cap-add=NET_ADMIN --cap-add=KILL --cap-add=SYS_TIME gremlin/gremlin syscheck

API Return codes


The Gremlin agent is unable to authenticate against the API. Causes of this error are usually due to bad or missing credentials files or certificates, or a revocation issued against the client.


  • 401 Unauthorized - Authorization header is missing or malformed
  • Client has been revoked (401 Unauthorized)
  • AUTH_RENEW: 401 Unauthorized


  • Ensure you have valid credentials (Certificates or API keys) being place in a location that Gremlin can read from.
  • Ensure Gremlin has proper read+write access to /var/lib/gremlin
  • Remove the file /var/lib/gremlin/.credentials if it exists
  • Re-run gremlin init

This error can also be the result of a race condition when Gremlin daemon is being started prior to the environment variables being exported.

In some specific cases, this error can also occur when multiple hosts or agents are configured with the same GREMLIN_IDENTIFIER. Common places this can occur:

  • Improperly configured ECS/Kubrenettes/Mesosphere where multiple Gremlin agents are assigned the same virtual IP
  • Missing HOST meta data on AWS/GCP/Azure which causes Gremlin to revert to the default localhost Identifier


The client limit for your company or team has been reached, Gremlin does not have a license to apply to the client.

You may terminate or revoke existing clients, or contact sales to increase the client limit.


The account, most likely trial account, has expired. Please contact sales to extend the trial.


This is most often attributed to a host having bad time data. Verify the system clock of the host and try again. If this problem persists past validating your hosts system clock, please reach out to support ASAP.


An error code of 409 indicates there is a conflicting attack running on the host. This is most often seen in the case of one network attack running (e.g a blackhole attack) and attempting to launch a second network attack. However, this can also be seen when trying to run two concurrent network or state attacks against the same target as well.