How to execute a shell command on an EC2 instance?

Question

Pulumi · Accepted Answer

In AWS, to execute a shell command on an EC2 instance, you use the `aws.ec2.Instance` class to create the instance. To run a shell command, you provide it as input to `userData` argument.

Remember to replace `"ami-abc12345"` with the actual AMI (Amazon Machine Image) ID that you plan to create a new EC2 instance from. Also, replace `"t2.micro"` with the desired instance type.

In this case, `userData` is a base64 encoded string. It includes a set of shell commands passed as user data to customize the instance. Please replace the shell script with the actual commands you want to execute.

Note that the command must exit with a 0 status for Pulumi to consider it successful. Also note that these commands run at system startup and require root privileges.

Here's a demonstration with Python:

```python
import pulumi
import pulumi_aws as aws

size = 't2.micro'
ami = aws.get_ami(most_recent="true",
                  owners=["137112412989"],  # This owner ID is for Amazon
                  filters=[{"name":"name","values":["amzn-ami-hvm-????.??.?.????????-x86_64-gp2"]}])  
# Use an AWS Linux AMI

user_data = '''#!/bin/bash
echo "Hello, World!" > index.html
nohup python -m SimpleHTTPServer 80 &
'''

group = aws.ec2.SecurityGroup('web-secgrp',
    description='Enable HTTP access',
    ingress=[
        { 'protocol': 'icmp', 'from_port': 8, 'to_port': 0, 'cidr_blocks': ['0.0.0.0/0'] },
        { 'protocol': 'tcp', 'from_port': 22, 'to_port': 22, 'cidr_blocks': ['0.0.0.0/0'] },
        { 'protocol': 'tcp', 'from_port': 80, 'to_port': 80, 'cidr_blocks': ['0.0.0.0/0'] },
    ])

server = aws.ec2.Instance('web-server-www',
    instance_type=size,
    vpc_security_group_ids=[group.id], # reference the group object above
    ami=ami.id,
    user_data=user_data,
    tags={"Name": "web-server-instance"},
    )

pulumi.export('publicIp', server.public_ip)
pulumi.export('publicHostName', server.public_dns)
```

When you run this Pulumi program, it will set up your EC2 instance and run the shell command you provided in the `user_data` argument. In this case, we are running a simple Python HTTP server. The server's public IP and hostname are then exported as stack outputs.