Getting Started > Enabling DNS collection

Enabling DNS collection

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Gremlin can collect information about the DNS queries on the Linux machines where the Gremlin Agent is installed. This DNS query information is a new way to define Services in Gremlin Reliability Management and helps inform Gremlin's Service features.

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What is collected?

For every DNS query visible to the Gremlin Agent, Gremlin will collect:

container ID
hostname in query
returned aliases from query
returned ip addresses from query

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Requirements

Using this feature requires the following:

Gremlin Agent version 2.40.1
Gremlin Kubernetes Chao version 0.3+
Gremlin must run within the PID namespace of the host; for Kubernetes this means setting hostPID=true
Gremlin needs the CAP_NET_RAW capability

DNS collection is experimental for Windows. User installation of WinPcap, Npcap, or Win10Pcap is required.

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Enable DNS Collection

To enable DNS Collection, use one of the following methods:

set ^{GREMLIN_COLLECT_DNS=true} in the Gremlin agent environment (by writing to ^{/etc/default/gremlind})
set ^{collect_dns: true} in /etc/gremlin/config.yaml

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Examples

The following sections show examples for enabling DNS Collection on your platform.

Existing installation

SHELL


sudo echo GREMLIN_COLLECT_DNS=true | sudo tee -a /etc/default/gremlind \
  && sudo systemctl restart gremlind

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APT

SHELL


echo "deb https://deb.gremlin.com/ release non-free" | sudo tee /etc/apt/sources.list.d/gremlin.list
   && sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 9CDB294B29A5B1E2E00C24C022E8EF3461A50EF6
   && sudo apt update
   && GREMLIN_COLLECT_DNS=true sudo -E apt install gremlin gremlind

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YUM

SHELL


sudo curl https://rpm.gremlin.com/gremlin.repo -o /etc/yum.repos.d/gremlin.repo \
  && GREMLIN_COLLECT_DNS=true sudo -E yum install gremlin gremlind

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Kubernetes

If you’re upgrading an existing Helm installation of the Gremlin Agent, run the following command with ^{helm upgrade} instead of ^{helm install}.

SHELL


helm repo add gremlin https://helm.gremlin.com
helm repo update
helm install gremlin gremlin/gremlin \
  --namespace gremlin \
  --set      gremlin.hostPID=true \
  --set      gremlin.collect.dns=true \
  --set      gremlin.secret.managed=true \
  --set      gremlin.secret.type=secret \
  --set      gremlin.secret.clusterID=my-cluster \
  --set      gremlin.secret.teamID=$GREMLIN_TEAM_ID \
  --set      gremlin.secret.teamSecret=$GREMLIN_TEAM_SECRET

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Docker

SHELL


docker run -d \
  --net=host \
  --pid=host \
  --cap-add=CAP_NET_RAW \
  -v /var/lib/gremlin:/var/lib/gremlin \
  -v /var/log/gremlin:/var/log/gremlin \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e GREMLIN_TEAM_ID \
  -e GREMLIN_TEAM_SECRET \
  -e GREMLIN_IDENTIFIER \
  -e GREMLIN_COLLECT_dns=true \
  gremlin/gremlin daemon

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Disable DNS Collection

DNS collection is disabled by default. To disable DNS Collection, use one of the following methods:

set ^{GREMLIN_COLLECT_DNS=false} in the Gremlin agent environment (by writing to ^{/etc/default/gremlind})
set ^{collect_dns: false} in /etc/gremlin/config.yaml

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Examples

The following sections show examples for disabling DNS Collection on your platform.

‍

Existing installation

SHELL


echo GREMLIN_COLLECT_DNS=false | sudo tee -a /etc/default/gremlind \
  && sudo systemctl restart gremlind

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APT

SHELL


echo "deb https://deb.gremlin.com/ release non-free" | sudo tee /etc/apt/sources.list.d/gremlin.list \
  && sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 9CDB294B29A5B1E2E00C24C022E8EF3461A50EF6 \
  && sudo apt update \
  && GREMLIN_COLLECT_DNS=false sudo -E apt install gremlin gremlind

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YUM

SHELL


sudo curl https://rpm.gremlin.com/gremlin.repo -o /etc/yum.repos.d/gremlin.repo \
  && GREMLIN_COLLECT_DNS=false sudo -E yum install gremlin gremlind

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Kubernetes

If you’re upgrading an existing Helm installation of the Gremlin Agent, run the following command with ^{helm upgrade} instead of ^{helm install}.

SHELL


helm repo add gremlin https://helm.gremlin.com
helm repo update
helm install gremlin gremlin/gremlin \
  --namespace gremlin \
  --set      gremlin.hostPID=true \
  --set      gremlin.collect.dns=false \
  --set      gremlin.secret.managed=true \
  --set      gremlin.secret.type=secret \
  --set      gremlin.secret.clusterID=my-cluster \
  --set      gremlin.secret.teamID=$GREMLIN_TEAM_ID \
  --set      gremlin.secret.teamSecret=$GREMLIN_TEAM_SECRET

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Docker

SHELL


docker run -d \
  --pid=host \
  --cap-add=NET_RAW \
  -v /var/lib/gremlin:/var/lib/gremlin \
  -v /var/log/gremlin:/var/log/gremlin \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e GREMLIN_TEAM_ID \
  -e GREMLIN_TEAM_SECRET \
  -e GREMLIN_IDENTIFIER \
  -e GREMLIN_COLLECT_DNS=false \
  gremlin/gremlin daemon

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