I've noticed that scripts run with CloudFormation's UserData attribute don't recognize the EC2 instance's shell variables. For example, the template section below doesn't print any values when provisioning. Is there any way to get around this?
UserData:
Fn::Base64: !Sub |
#!/bin/bash
echo HOME: $HOME
echo USER: $USER
echo PATH: $PATH
Note that the environment where cloud-init's User-Data Script gets executed doesn't usually contain HOME and USER variables, since the script is executed as root in a non-login shell.
Try the env command in your UserData to see the full list of environment variables available:
Description: Output shell variables.
Resources:
Instance:
Type: AWS::EC2::Instance
Properties:
ImageId: ami-9be6f38c # amzn-ami-hvm-2016.09.1.20161221-x86_64-gp2
InstanceType: m3.medium
UserData:
Fn::Base64: !Sub |
#!/bin/bash
env
On an Amazon Linux AMI (note that the result will depend on the AMI you're running!), I get the following output in the Console Output:
TERM=linux
PATH=/sbin:/usr/sbin:/bin:/usr/bin
RUNLEVEL=3
runlevel=3
PWD=/
LANGSH_SOURCED=1
LANG=en_US.UTF-8
PREVLEVEL=N
previous=N
CONSOLETYPE=serial
SHLVL=4
UPSTART_INSTANCE=
UPSTART_EVENTS=runlevel
UPSTART_JOB=rc
_=/bin/env