Use tmux to ssh to all instances of an AWS autoscaling group and execute commands simultaneously.

aws_autoscaling_multi_ssh.sh

#!/bin/bash
#
#                _                         _                 _
#    ____       | |                       | |               | |
#   / __ \  __ _| |__  _ __ ___   __ _  __| |_ __   ___  ___| |_ ___ _ __
#  / / _` |/ _` | '_ \| '_ ` _ \ / _` |/ _` | '_ \ / _ \/ __| __/ _ \ '_ \
# | | (_| | (_| | | | | | | | | | (_| | (_| | |_) | (_) \__ \ ||  __/ | | |
#  \ \__,_|\__,_|_| |_|_| |_| |_|\__,_|\__,_| .__/ \___/|___/\__\___|_| |_|
#   \____/                                  | |
#                                           |_|
#####################################################
#
# Use this script to ssh to multiple instances in an AWS autoscaling group using tmux. It synchronizes all the panes
# so you can execute the same command on all of the machines simultaneously. Dependences are tmux and aws cli. AWS cli
# needs to be configured
# configurations.

# You have to set these before running the script
AUTO_SCALING_GROUP_NAME="my group name"
SSH_KEY_PATH="my key path"
USER="my username (the ssh user)"

if ! command -v "aws" >/dev/null 2>&1; then
  echo "AWS cli is not installed. please follow 'http://docs.aws.amazon.com/cli/latest/userguide/installing.html'"
fi;

if ! command -v "tmux" >/dev/null 2>&1; then
  echo "Please install tmux";
fi;

HOSTS=( $(aws --output text --query "Reservations[*].Instances[*].PublicIpAddress" ec2 describe-instances --instance-ids\
  `aws --output text --query "AutoScalingGroups[0].Instances[*].InstanceId" autoscaling describe-auto-scaling-groups \
  --auto-scaling-group-names "$AUTO_SCALING_GROUP_NAME"` | tr "\n" " " | tr "\t" " "))

tmux new-window "ssh $USER@${HOSTS[0]} -i $SSH_KEY_PATH"
HOSTS=("${HOSTS[@]:1}")

for i in "${HOSTS[@]}"; do
  tmux split-window -h  "ssh $USER@$i -i $SSH_KEY_PATH"
  tmux select-layout tiled > /dev/null
done

tmux select-pane -t 0
tmux set-window-option synchronize-panes on > /dev/null

DEMO