EC2 Scripts

Link post

I do a lot of work on ec2 instances, and one thing that makes this easier is having a few scripts for manipulating them. These are very small, small enough to go in my .bashrc, but still make my life a lot easier.

The first one is start_ec2:

alias start_ec2=‘aws ec2 start-instances—instance-ids i-NNNN’

I have an instance I do most of my work on, and this command starts it. Way better than logging into the AWS Console like I used to do.

After a few seconds I run:

function ssh_ec2() {
  ADDR=”$(aws ec2 describe-instances \
           --instance-ids i-NNNN \
           --query ‘Reservations[].Instances[].PublicDnsName’
           --output text)”
  if [ $? != 0 ] || [ -z “$ADDR” ]; then
    echo “Instance not running.”
    return
  fi

  scp “ec2-user@$ADDR:.full_history” \
      /path/to/ec2-full-history-backup.txt

  ssh “ec2-user@$ADDR”
}

This figures out the IP of the instance, copies down my (very important) full shell history, and logs me in over ssh.

I don’t have a command for shutting down remotely: I just run sudo shutdown -h now while logged in.

The last command, and probably my favorite, is resize_ec2:

function resize_ec2j() {
  aws ec2 modify-instance-attribute \
   --instance-id i-NNNN \
   --instance-type “$1”
}

For example, resize_ec2 c6a.xlarge or resize_ec2 c6a.32xlarge. Depending on what I’m doing I might need very different specs, and I don’t want to pay $4.90/hr when I only need a $0.15/hr machine. It does take a mildly annoying few minutes for a machine that has just shut down to transition into a state where you can resize it, but it’s not too bad.