# Creating, configuring, and deleting Amazon EC2 security groups in the Amazon CLI
You can create a security group for your Amazon Elastic Compute Cloud (Amazon EC2) instances that essentially operates as a firewall, with rules that determine what network traffic can enter and leave.
Use the Amazon Command Line Interface (Amazon CLI) to create a security group, add rules to existing security groups, and delete security groups.
**Note**
For additional command examples, see the [Amazon CLI reference guide](https://docs.amazonaws.cn/cli/latest/reference/index.html).
**Topics**
+ [Prerequisites](#cli-services-ec2-sg-prereqs)
+ [Create a security group](#creating-a-security-group)
+ [Add rules to your security group](#configuring-a-security-group)
+ [Delete your security group](#deleting-a-security-group)
+ [References](#cli-services-ec2-sg-references)
## Prerequisites
To run the `ec2` commands, you need to:
+ Install and configure the Amazon CLI. For more information, see [Installing or updating to the latest version of the Amazon CLI](getting-started-install.md) and [Authentication and access credentials for the Amazon CLI](cli-chap-authentication.md).
+ Set your IAM permissions to allow for Amazon EC2 access. For more information about IAM permissions for Amazon EC2, see [IAM policies for Amazon EC2](https://docs.amazonaws.cn/AWSEC2/latest/UserGuide/iam-policies-for-amazon-ec2.html) in the *Amazon EC2 User Guide*.
## Create a security group
You can create security groups associated with virtual private clouds (VPCs) .
The following `[aws ec2 create-security-group](https://docs.amazonaws.cn/cli/latest/reference/ec2/create-security-group.html)` example shows how to create a security group for a specified VPC.
```
$ aws ec2 create-security-group --group-name my-sg --description "My security group" --vpc-id vpc-1a2b3c4d
{
"GroupId": "sg-903004f8"
}
```
To view the initial information for a security group, run the `[aws ec2 describe-security-groups](https://docs.amazonaws.cn/cli/latest/reference/ec2/describe-security-groups.html)` command. You can reference an EC2-VPC security group only by its `vpc-id`, not its name.
```
$ aws ec2 describe-security-groups --group-ids sg-903004f8
{
"SecurityGroups": [
{
"IpPermissionsEgress": [
{
"IpProtocol": "-1",
"IpRanges": [
{
"CidrIp": "0.0.0.0/0"
}
],
"UserIdGroupPairs": []
}
],
"Description": "My security group"
"IpPermissions": [],
"GroupName": "my-sg",
"VpcId": "vpc-1a2b3c4d",
"OwnerId": "123456789012",
"GroupId": "sg-903004f8"
}
]
}
```
## Add rules to your security group
When you run an Amazon EC2 instance, you must enable rules in the security group to allow incoming network traffic for your means of connecting to the image.
For example, if you're launching a Windows instance, you typically add a rule to allow inbound traffic on TCP port 3389 to support Remote Desktop Protocol (RDP). If you're launching a Linux instance, you typically add a rule to allow inbound traffic on TCP port 22 to support SSH connections.
Use the `[aws ec2 authorize-security-group-ingress](https://docs.amazonaws.cn/cli/latest/reference/ec2/authorize-security-group-ingress.html)` command to add a rule to your security group. A required parameter of this command is the public IP address of your computer, or the network (in the form of an address range) that your computer is attached to, in [CIDR](https://wikipedia.org/wiki/Classless_Inter-Domain_Routing) notation.
The following example shows how to add a rule for RDP (TCP port 3389) to an EC2-VPC security group with the ID `sg-903004f8` using your IP address.
To start, find your IP address.
```
$ curl https://checkip.amazonaws.com
x.x.x.x
```
You can then add the IP address to your security group by running the `[aws ec2 authorize-security-group-ingress](https://docs.amazonaws.cn/cli/latest/reference/ec2/authorize-security-group-ingress.html)` command.
```
$ aws ec2 authorize-security-group-ingress --group-id sg-903004f8 --protocol tcp --port 3389 --cidr x.x.x.x/x
```
The following command adds another rule to enable SSH to instances in the same security group.
```
$ aws ec2 authorize-security-group-ingress --group-id sg-903004f8 --protocol tcp --port 22 --cidr x.x.x.x/x
```
To view the changes to the security group, run the `[aws ec2 describe-security-groups](https://docs.amazonaws.cn/cli/latest/reference/ec2/describe-security-groups.html)` command.
```
$ aws ec2 describe-security-groups --group-ids sg-903004f8
{
"SecurityGroups": [
{
"IpPermissionsEgress": [
{
"IpProtocol": "-1",
"IpRanges": [
{
"CidrIp": "0.0.0.0/0"
}
],
"UserIdGroupPairs": []
}
],
"Description": "My security group"
"IpPermissions": [
{
"ToPort": 22,
"IpProtocol": "tcp",
"IpRanges": [
{
"CidrIp": "x.x.x.x/x"
}
]
"UserIdGroupPairs": [],
"FromPort": 22
}
],
"GroupName": "my-sg",
"OwnerId": "123456789012",
"GroupId": "sg-903004f8"
}
]
}
```
## Delete your security group
To delete a security group, run the `[aws ec2 delete-security-group](https://docs.amazonaws.cn/cli/latest/reference/ec2/delete-security-group.html)` command.
**Note**
You can't delete a security group if it's currently attached to an environment.
The following command example deletes an EC2-VPC security group.
```
$ aws ec2 delete-security-group --group-id sg-903004f8
```
## References
**Amazon CLI reference:**
+ `[aws ec2](https://docs.amazonaws.cn/cli/latest/reference/ec2/index.html)`
+ `[aws ec2 authorize-security-group-ingress](https://docs.amazonaws.cn/cli/latest/reference/ec2/authorize-security-group-ingress.html)`
+ `[aws ec2 create-security-group](https://docs.amazonaws.cn/cli/latest/reference/ec2/create-security-group.html)`
+ `[aws ec2 delete-security-group](https://docs.amazonaws.cn/cli/latest/reference/ec2/delete-security-group.html)`
+ `[aws ec2 describe-security-groups](https://docs.amazonaws.cn/cli/latest/reference/ec2/describe-security-groups.html)`
**Other reference:**
+ [Amazon Elastic Compute Cloud Documentation](https://docs.amazonaws.cn/ec2/)
+ To view and contribute to Amazon SDK and Amazon CLI code examples, see the [Amazon Code Examples Repository](https://github.com/awsdocs/aws-doc-sdk-examples/) on *GitHub*.