Wait Until SSH Is Available

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[Author’s Note in 2021: This is old and should not be used for modern deployments as-is but is kept for historical reasons]

Ever run into a situation where you need to ssh into a newly created server but you aren’t sure that the server is listening on the ssh port yet? For the Terraform OpenStack install of Cloud Foundry the Bastion server isn’t immediately available for the provision script to run.

Below is a short bash script that will wait until ssh is available on the target server. If the server isn’t ready yet, wait 10 seconds and try again for a maximum of 10 attempts.

#Wait until SSH on Bastion server is working
keyPath=$(terraform output key_path | sed -e "s#^~#$HOME#")
scriptPath="provision/provision.sh"
targetPath="/home/ubuntu/provision.sh"
bastionIP=$(terraform output bastion_ip)
maxConnectionAttempts=10
sleepSeconds=10

#Wait until SSH on Bastion server is working
echo "Attempting to SSH to Bastion server..."
index=1

while (( $index <= $maxConnectionAttempts ))
do
  ssh -i ${keyPath} ubuntu@$bastionIP
  case $? in
    (0) echo "${index}> Success"; break ;;
    (*) echo "${index} of ${maxConnectionAttempts}> Bastion SSH server not ready yet, waiting ${sleepSeconds} seconds..." ;;
  esac
  sleep $sleepSeconds
  ((index+=1))
done

Enjoy!

Brain Droppings

Wait Until SSH Is Available