Run commands over SSH!

There are times where I need to run a few command on a server. In the past, I would SSH into the server and I would start making changes. But this is not ideal; since this it’s not repeatable. If you’ve run into this problem, I have an alternative! You can run commands over SSH! The script is executed on your machine but then the commands are run on the remote machine.

Please be aware that there are better tools – Ansible, Terraform, CloudFormation, etc. But those are heavy tools.

In this example, I have some configuration files that need to be copied to the remote system, and then I need to execute a couple commands. I also wanted the script to be checked into version control.

The first half of the script copies files, using scp, from my local machine to the remote machine. The second half of the script (starting on line 12) runs commands from the remote machine. The files are moved to the correct locations and Nginx and Haproxy are restarted.

#!/bin/bash

PEM=id_rsa.pub
HOST=ec2-54-234-130-49.compute-1.amazonaws.com

scp -i ~/.ssh/$PEM ./surrogate_pop.conf ubuntu@$HOST:/tmp
scp -i ~/.ssh/$PEM ./haproxy.cfg ubuntu@$HOST:/tmp
scp -i ~/.ssh/$PEM ./traffic_cop.lua ubuntu@$HOST:/tmp
scp -i ~/.ssh/$PEM ./allowed_domains.lua ubuntu@$HOST:/tmp

## These are executed on the remote host
ssh -i ~/.ssh/$PEM ubuntu@$HOST 'bash -s' <<EOF
sudo mv /tmp/traffic_cop.lua /usr/share/nginx/traffic_cop.lua
sudo mv /tmp/allowed_domains.lua /usr/share/nginx/allowed_domains.lua
sudo mv /tmp/surrogate_pop.conf /etc/nginx/sites-enabled/surrogate_pop.conf
sudo service nginx restart

sudo mv /tmp/haproxy.cfg /etc/haproxy/haproxy.cfg
sudo service haproxy restart
EOF