Guide to creating a Kubernetes Cluster in existing subnets & VPC on AWS with kops

This article is a guide on how to setup a Kubernetes cluster in AWS using kops and plugging it into your own subnets and VPC. We attempt to minimise the external IPs used in this method.

Export your AWS API keys into environment variables

export AWS_ACCESS_KEY_ID='YOUR_KEY'
export AWS_SECRET_ACCESS_KEY='YOUR_ACCESS_KEY'
export CLUSTER_NAME="my-cluster-name"
export VPC="vpc-xxxxxx"
export K8SSTATE="s3-k8sstate"</pre>

Create the cluster (you can change some of these switches to match your requirements. I would suggest only using one worker node and one master node to begin with and then increase them once you have confirmed the config is good. The more workers and master nodes you have, the longer it will take to run a rolling-update.

kops create cluster --cloud aws --name $CLUSTER_NAME --state s3://$K8SSTATE --node-count 1 --zones eu-west-1a,eu-west-1b,eu-west-1c --node-size t2.micro --master-size t2.micro --master-zoneseu-west-1a,eu-west-1b,eu-west-1c --ssh-public-key ~/.ssh/id_rsa.pub --topology=private --networking=weave --associate-public-ip=false --vpc $VPC

Important note: There must be an ODD number of master zones. If you tell kops to use an even number zones for master, it will complain.

If you want to use additional security groups, don’t add them yet — add them after you have confirmed the cluster is working.

Internal IPs: You must have a VPN connection into your VPC or you will not be able to ssh into the instances. The alternative is to use the bastion functionality using the --bastion flag with the create command. Then doing this:

ssh -i ~/.ssh/id_rsa -o ProxyCommand='ssh -W %h:%p admin@bastion.$CLUSTER_NAME' admin@INTERNAL_MASTER_IP

However, if you do this method, you MUST then use public IP addressing on the api load balancer, as you will not be able to do kops validate otherwise.

Edit the cluster

kops edit cluster $CLUSTER_NAME --state=s3://$K8SSTATE

Make the following changes:

If you have a VPN connection into the VPC, change spec.api.loadBalancer.type to “Internal“, otherwise, leave it as “Public
Change spec.subnets to match your private subnets. To use existing private subnets, they should also include the id of the subnet and match the CIDR range, e.g.:

subnets:
- cidr: 10.10.10.0/23
  id: subnet-xxxxxxx
  name: eu-west-1a
  type: Private
  zone: eu-west-1a</pre>

The utility subnet is where the Bastion hosts will be placed, and these should be in a public subnet, since they will be the inbound route into the cluster from the internet.

If you need to change or add specific IAM permissions, add them under spec.additionalPolicies like this to add additional policies to the node IAM policy (apologies about the formatting. WordPress is doing something weird to it.)

additionalPolicies:
  node: | 
    [ 
      {  
        "Effect": "Allow", 
        "Action": ["dynamodb:*"],
        "Resource": ["*"] 
      },  
      {  
        "Effect": "Allow",  
        "Action": ["es:*"],     
        "Resource": ["*"]     
      }    
    ]

Edit the bastion, nodes, and master configs (MASTER_REGION is the zone where you placed the master. If you are running a multi-region master config, you’ll have to do this for each region)

kops edit ig master-{MASTER_REGION} --name=$CLUSTER_NAME --state s3://$K8SSTATE

kops edit ig nodes --name=$CLUSTER_NAME --state s3://$K8SSTATE
kops edit ig bastions --name=$CLUSTER_NAME --state s3://$K8SSTATE

Check and make any updates.

If you want a mixture of instance types (e.g. t2.mediums and r3.larges), you’ll need to separate these using new instance groups ($SUBNETS is the subnets where you want the nodes to appear — for example, you can provide a list “eu-west-2a,eu-west-2b)

kops create ig anothernodegroup --state s3://$K8SSTATE --subnets $SUBNETS

You can later delete this with

kops delete ig anothernodegroup --state s3://$K8SSTATE

If you want to use spot prices, add this under the spec section (x.xx is the price you want to bid):

maxPrice: "x.xx"

Check the instance size and count if you want to change them (I would recommend not changing the node count just yet)

If you want to add tags to the instances (for example for billing), add something like this to the spec section:

cloudLabels:
  Billing: product-team</pre>

If you want to run some script(s) at node startup (cloud-init), add them to spec.additionalUserData:

spec:
  additionalUserData:
  - name: myscript.sh
    type: text/x-shellscript
    content: |
      #!/bin/sh
      echo "Hello World.  The time is now $(date -R)!" | tee /root/output.txt

Apply the update:

kops update cluster $CLUSTER_NAME --state s3://$K8SSTATE --yes

Wait for DNS to propagate and then validate

kops validate cluster --state s3://$K8SSTATE

Once the cluster returns ready, apply the Kubernetes dashboard

kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/master/src/deploy/alternative/kubernetes-dashboard.yaml

Access the dashboard via

https://api.$CLUSTER_NAME/api/v1/namespaces/kube-system/services/kubernetes-dashboard/proxy/

(ignore the cert error)

Username is “admin” and the password is found from your local ~/.kube/config

Add the External DNS update to allow you to give friendly names to your externally-exposed services rather than the horrible elb names.

See here: https://github.com/kubernetes-incubator/external-dns/blob/master/docs/tutorials/aws.md

(You can apply the yaml directly onto the cluster via the dashboard. Make sure you change the filter to match your domain or subdomain. )

Note that if you use this, you’ll need to change the node IAM policy on the cluster config as the default IAM policy won’t allow the External DNS container to modify Route 53 entries, and also annotate (use kubectl annotate $service_name key:value) your service with text such as:

external-dns.alpha.kubernetes.io/hostname: $SERVICE_NAME.$CLUSTERNAME

And also you might need this annotation, to make the ELB internal rather than public – otherwise Kubernetes will complain “Error creating load balancer (will retry): Failed to ensure load balancer for service namespace/service: could not find any suitable subnets for creating the ELB”

service.beta.kubernetes.io/aws-load-balancer-internal: 0.0.0.0/0

(Optional) Add the Cockpit pod to your cluster as described here

http://cockpit-project.org/guide/133/feature-kubernetes.html

It will allow you to visually see a topology of your cluster at a cluster and also provides some management features too. For example, here’s my cluster. It contains 5 nodes (1 master, 4 workers and is running 4 services (Kubernetes, external-dns, cockpit, and dashboard). Cockpit creates a replication controller so it knows about the changes.

chrome_2018-01-14_15-44-00

Add any additional security groups by adding this under the spec section of the node/master/bastions config, then do a rolling-update (you might need to use the --force switch), do this as soon as you can after creating and verifying the cluster updates work.

additionalSecurityGroups:
- sg-xxxxxxxx
- sg-xxxxxxxx

If the cluster breaks after this (i.e. the nodes haven’t shown up on the master), reboot the server (don’t terminate, use the reboot option from the AWS console), and see if that helps. If it still doesn’t show up, there’s something wrong with the security groups attached — i.e. they’re conflicting somehow with the Kubernetes access. Remove those groups and then do another rolling-update but use both the --force and --cloudonly switches to force a “dirty” respin.

If the cluster comes up good, then you can change the node counts on the configs and apply the update.

Note that if you change the node count and then apply the update, the cluster attempts to make the update without rolling-update. For example, if you change the node count from 1 to 3, the cluster attempts to bring up the 2 additional nodes.

Other things you can look at:

Kompose – which converts a docker-compose configuration into Kubernetes resources

Finally, have fun!

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