How to add a security group to a running EC2 Instance?

Solution 1:

Update: As of January 2014, you can now change security groups for running AWS EC2 instances.

AWS Console

Simply right-click on an instance, and click on Change Security Group

Add/remove security groups as appropriate and click Assign Security Groups when done

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EC2 Command Line

Use the following command:

ec2-modify-instance-attribute <instance-id> --group-id <group-id>

AWS Command Line

Use the following command:

aws ec2 modify-instance-attribute --instance-id i-12345 --groups sg-12345 sg-67890

Note, you must specify all security groups with which you'd like the instance associated.

Solution 2:

Update 2015-02-27:

This is now possible, see the answer below.

Old reply:

Amazon's FAQ says it's not possible to define a security group anywhere but at launch time.

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Solution 3:

It is now possible to do this. Click on the actions menu and Change Security Groups - Select the Security Groups you would like to use.

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Solution 4:

1. Create an AMI image from the instance you want to move to a different security group.
2. Launch a new instance using that image, now we can assign this new instance to a different security group.
3. Discard the previous instance.

This requires downtime on your instance. There may be some other options available using the API.

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Solution 5:

As towo said you can't change a security group of an instance anywhere but launch time.

Unless you are using a VPC where security groups differ from EC2 security groups.

This page outlines the differences between EC2 and VPC security groups.

http://docs.amazonwebservices.com/AmazonVPC/latest/UserGuide/VPC_SecurityGroups.html

So if you require the extra functionality of the VPC groups (Changing groups, control ingress/engress traffic, etc.), you may want to look at the additional functionality provided by VPCs.