SSH wrapper to convert EC2 private DNS names into IPs.
There's probably other use cases but mine is simple: I grew tired of having to hand edit EC2 private DNS names to ssh into them.
kubectl get nodes outputs a list of Kubernetes node names and status. If the cluster is composed of AWS EC2 instances the output looks like:
$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
ip-1-2-3-4.us-east-1.compute.internal Ready <none> 3d23h v1.19.15-eks-9c63c4
ip-1-2-3-5.us-east-1.compute.internal Ready <none> 3d23h v1.19.15-eks-9c63c4
ip-42-42-42-42.us-east-1.compute.internal Ready <none> 3d23h v1.19.15-eks-9c63c4
ip-42-42-42-43.us-east-1.compute.internal Ready <none> 3d23h v1.19.15-eks-9c63c4When for whatever reason (i.e. a node is in NotReady status) I want to ssh into a node I just want to copypaste the node name and ssh into it without having to hand edit it and convert it into an actual IP, or without having to run an additional kubectl describe <NODE> or some jq parsing to get the node IP.
So this ssh wrapper checks the host address and if it matches the EC2 private DNS name pattern it converts it into the actual instance IP before sshing into it.
The most usual method is to simply copypaste the ssh() function into your shell RC file: ~/.bashrc for Bash, ~/.zshrc for Zsh, etc. Then run source <RC_file> or simply open a new shell and your wrapper will be in place.
Run which ssh to check whether the installation was correct. Output should show the wrapper instead of /usr/bin/ssh.
Once installed, just ssh normally but using the EC2 private DNS name instead. All passed in parameters (including the user in the form user@host) should just work.
$ ssh -i ~/.ssh/my_key.pem ec2-user@ip-1-2-3-4.us-east-1.compute.internal
Warning: Permanently added '1.2.3.4' (ED25519) to the list of known hosts.
Last login: Sun Jan 23 03:49:57 2022 from 4.3.2.1
__| __|_ )
_| ( / Amazon Linux 2 AMI
___|\___|___|
https://aws.amazon.com/amazon-linux-2/
6 package(s) needed for security, out of 17 available
Run "sudo yum update" to apply all updates.
[ec2-user@ip-1-2-3-4 ~]$
Tested in bash and zsh.