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Common delegate initialization scripts

You can run scripts on Harness Delegate pods, hosts, and containers to install applications or run commands.

For more information about running scripts, go to Build custom delegate images with third-party tools. This topic provides information on script availability and some common delegate initialization scripts.

Limitations​

  • When you edit or delete scripts, the binaries that were already installed by those scripts are not automatically removed. To remove them, you must restart or clean up the pod or VM.
  • You cannot use Harness secrets in scripts. This is because the script runs before the delegate is registered with and establishes a connection to Harness.

Review: What can I run In a script?​

You can add any command that the host, container, or pod running the delegate supports. Linux shell commands are most common. If kubectl, Helm, or Docker is running on the host, container, or pod where you install the delegate, you can use those commands. Kubernetes and Docker delegates include Helm.

The base image for the delegate uses the Red Hat Universal Base Image (Red Hat/UBI8). This means you can use any default Red Hat package in the delegate script.

Harness Delegate​

Harness Delegate is packaged with cURL and tar.

When is the script executed?​

Delegate scripts are applied under the following conditions:

  • New Delegate. Scripts added on delegate creation run before the delegate starts.
  • Running Delegate. Scripts applied during delegate runtime, either by application as a new script or by switching the Delegate's current script, run on delegate restart, before the delegate reaches steady state.

Unzip​

Run microdnf update before you run microdnf commands.

microdnf update
# Install Unzip
microdnf install unzip

Terraform​

Here is an example of a script for installing Terraform:

# Install jq and unzip for JSON parsing and unzipping files
microdnf install jq unzip
# Fetch the latest Terraform version
latest_version=$(curl -s https://checkpoint-api.hashicorp.com/v1/check/terraform | jq -r .current_version)
# Download the latest Terraform version
curl -O -L "https://releases.hashicorp.com/terraform/${latest_version}/terraform_${latest_version}_linux_amd64.zip"
# Unzip and move Terraform to your bin directory
unzip "terraform_${latest_version}_linux_amd64.zip"
mv terraform /usr/bin/
# Cleanup downloaded zip file
rm "terraform_${latest_version}_linux_amd64.zip"
# Check Terraform installation
terraform --version

Helm 3​

You do not need to add a script for Helm 3. Harness includes Helm 3 support in any Delegate that can connect to the target Kubernetes cluster.

Pip​

Run microdnf update before you run microdnf commands.

microdnf update
# Install pip
microdnf -y install python3-pip
# Check pip install
pip -v

AWS CLI​

The following script installs the AWS CLI version 2 on the delegate host.

# Install AWS CLI
curl "https://awscli.amazonaws.com/awscli-exe-linux-x86_64.zip" -o "awscliv2.zip"
unzip awscliv2.zip
./awscli-bundle/install -b ~/bin/aws
# install
./aws/install
# Check AWS CLI install
aws --version

AWS describe instance​

The following script describes the EC2 instance based on its private DNS hostname:

aws ec2 describe-instances --filters "Name=network-interface.private-dns-name,Values=ip-10-0-0-205.ec2.internal" --region "us-east-1"

The value for the Values parameter is the hostname of the delegate.

AWS List All Instances in a Region​

The following script lists all the EC2 instances in the region you specify:

aws ec2 describe-instances --query 'Reservations[*].Instances[*].[InstanceId,State.Name,InstanceType,PrivateIpAddress,PublicIpAddress,Tags[?Key==`Name`].Value[]]' --region "us-east-1" --output json | tr -d '\n[] "' | perl -pe 's/i-/\ni-/g' | tr ',' '\t' | sed -e 's/null/None/g' | grep '^i-' | column -t

Git CLI​

Run microdnf update before you run microdnf commands.

microdnf update
# Install Git with auto approval
microdnf -y install git
# Check git install
git --version

Cloud Foundry CLI​

Harness supports Cloud Foundry (CF) CLI version 7 only. Below is an example of CF CLI installation; the version of the CF CLI that you install on the delegate should match the PCF features you use in your Harness PCF deployment.

For example, if you are using buildpacks in the manifest.yml file of your Harness service, the CLI you install on the delegate must be the same version or later.

The following example script installs Cloud Foundry CLI on a delegate:

wget -O /etc/yum.repos.d/cloudfoundry-cli.repo https://packages.cloudfoundry.org/fedora/cloudfoundry-cli.repo

microdnf -y install cf-cli

The -y parameter is needed for a prompt.

When the script has been applied and you click the timestamp for the Delegate the output will be similar to this:

Running transaction
  Installing : cf-cli-6.46.1-1.x86_64                                       1/1
  Verifying  : cf-cli-6.46.1-1.x86_64                                       1/1

Installed:
  cf-cli.x86_64 0:6.46.1-1

Complete!

For information on installing the CLI on different distributions, go to Installing the cf CLI from PCF.