Chapter 5. Accessing an FTP server using Skupper Securely connect to an FTP server on a remote Kubernetes cluster This example is part of a suite of examples showing the different ways you can use Skupper to connect services across cloud providers, data centers, and edge sites. Overview This example shows you how you can use Skupper to connect an FTP client on one Kubernetes cluster to an FTP server on another. It demonstrates use of Skupper with multi-port services such as FTP. It uses FTP in passive mode (which is more typical these days) and a restricted port range that simplifies Skupper configuration. Prerequisites The kubectl command-line tool, version 1.15 or later ( installation guide ) Access to at least one Kubernetes cluster, from any provider you choose Procedure Clone the repo for this example. Install the Skupper command-line tool Set up your namespaces Deploy the FTP server Create your sites Link your sites Expose the FTP server Run the FTP client Clone the repo for this example. Navigate to the appropriate GitHub repository from https://skupper.io/examples/index.html and clone the repository. Install the Skupper command-line tool This example uses the Skupper command-line tool to deploy Skupper. You need to install the skupper command only once for each development environment. See the Installation for details about installing the CLI. For configured systems, use the following command: Set up your namespaces Skupper is designed for use with multiple Kubernetes namespaces, usually on different clusters. The skupper and kubectl commands use your kubeconfig and current context to select the namespace where they operate. Your kubeconfig is stored in a file in your home directory. The skupper and kubectl commands use the KUBECONFIG environment variable to locate it. A single kubeconfig supports only one active context per user. Since you will be using multiple contexts at once in this exercise, you need to create distinct kubeconfigs. For each namespace, open a new terminal window. In each terminal, set the KUBECONFIG environment variable to a different path and log in to your cluster. Then create the namespace you wish to use and set the namespace on your current context. Note The login procedure varies by provider. See the documentation for yours: Amazon Elastic Kubernetes Service (EKS) Azure Kubernetes Service (AKS) Google Kubernetes Engine (GKE) IBM Kubernetes Service OpenShift Public: Private: Deploy the FTP server In Private, use kubectl apply to deploy the FTP server. Private: Sample output: Create your sites A Skupper site is a location where components of your application are running. Sites are linked together to form a network for your application. In Kubernetes, a site is associated with a namespace. For each namespace, use skupper init to create a site. This deploys the Skupper router and controller. Then use skupper status to see the outcome. Public: Sample output: Private: Sample output: As you move through the steps below, you can use skupper status at any time to check your progress. Link your sites A Skupper link is a channel for communication between two sites. Links serve as a transport for application connections and requests. Creating a link requires use of two skupper commands in conjunction, skupper token create and skupper link create . The skupper token create command generates a secret token that signifies permission to create a link. The token also carries the link details. Then, in a remote site, The skupper link create command uses the token to create a link to the site that generated it. Note The link token is truly a secret. Anyone who has the token can link to your site. Make sure that only those you trust have access to it. First, use skupper token create in site Public to generate the token. Then, use skupper link create in site Private to link the sites. Public: Sample output: Private: Sample output: If your terminal sessions are on different machines, you may need to use scp or a similar tool to transfer the token securely. By default, tokens expire after a single use or 15 minutes after creation. Expose the FTP server In Private, use skupper expose to expose the FTP server on all linked sites. Private: Sample output: Run the FTP client In Public, use kubectl run and the curl image to perform FTP put and get operations. Public: Sample output:

Commands:
sudo dnf install skupper-cli
export KUBECONFIG=~/.kube/config-public Enter your provider-specific login command create namespace public config set-context --current --namespace public
export KUBECONFIG=~/.kube/config-private Enter your provider-specific login command create namespace private config set-context --current --namespace private
apply -f server
kubectl apply -f server deployment.apps/ftp-server created
skupper init skupper status
skupper init Waiting for LoadBalancer IP or hostname Waiting for status Skupper is now installed in namespace 'public'. Use 'skupper status' to get more information. skupper status Skupper is enabled for namespace "public". It is not connected to any other sites. It has no exposed services.
skupper init skupper status
skupper init Waiting for LoadBalancer IP or hostname Waiting for status Skupper is now installed in namespace 'private'. Use 'skupper status' to get more information. skupper status Skupper is enabled for namespace "private". It is not connected to any other sites. It has no exposed services.
skupper token create ~/secret.token
skupper token create ~/secret.token Token written to ~/secret.token
skupper link create ~/secret.token
skupper link create ~/secret.token Site configured to link to https://10.105.193.154:8081/ed9c37f6-d78a-11ec-a8c7-04421a4c5042 (name=link1) Check the status of the link using 'skupper link status'.
skupper expose deployment/ftp-server --port 21100 --port 21
skupper expose deployment/ftp-server --port 21100 --port 21 deployment ftp-server exposed as ftp-server
echo "Hello!" | kubectl run ftp-client --stdin --rm --image=docker.io/curlimages/curl --restart=Never -- -s -T - ftp://example:example@ftp-server/greeting run ftp-client --attach --rm --image=docker.io/curlimages/curl --restart=Never -- -s ftp://example:example@ftp-server/greeting
echo "Hello!" | kubectl run ftp-client --stdin --rm --image=docker.io/curlimages/curl --restart=Never -- -s -T - ftp://example:example@ftp-server/greeting pod "ftp-client" deleted kubectl run ftp-client --attach --rm --image=docker.io/curlimages/curl --restart=Never -- -s ftp://example:example@ftp-server/greeting Hello! pod "ftp-client" deleted