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codeinthehole/user-data.sh

Created August 18, 2014 12:41
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  1. codeinthehole created this gist Aug 18, 2014.
    37 changes: 37 additions & 0 deletions user-data.sh
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    #!/usr/bin/env bash
    #
    # Get the value of a tag for a running EC2 instance.
    #
    # This can be useful within bootstrapping scripts ("user-data").
    #
    # Note the EC3 instance needs to have an IAM role that lets it read tags. The policy
    # JSON for this looks like:
    #
    # {
    # "Version": "2012-10-17",
    # "Statement": [
    # {
    # "Effect": "Allow",
    # "Action": "ec2:DescribeTags",
    # "Resource": "*"
    # }
    # ]
    # }

    # Define the tag you want to get the value for
    KEY=bucket

    # Install AWS CLI (you could just do 'apt-get install awscli' although you'll
    # get an older version).
    apt-get update
    apt-get install -y python-pip
    pip install -U pip
    pip install awscli

    # Grab instance ID and region as the 'describe-tags' action below requires them. Getting the region
    # is a pain (see http://stackoverflow.com/questions/4249488/find-region-from-within-ec2-instance)
    INSTANCE_ID=$(ec2metadata --instance-id)
    REGION=$(curl -s http://169.254.169.254/latest/dynamic/instance-identity/document | grep region | awk -F\" '{print $4}')

    # Grab tag value
    TAG_VALUE=$(aws ec2 describe-tags --filters "Name=resource-id,Values=$INSTANCE_ID" "Name=key,Values=$KEY" --region=$REGION --output=text | cut -f5)