Amazon EC2 Compute

Best experience with the AWS MCP server; also works with the AWS CLI alone — no hard dependency on either.

Critical Warnings

Launch configurations are deprecated and do not support current EC2 instance types; new accounts cannot create them. Use launch templates for every new Auto Scaling group. See auto-scaling.md.

ASGs ignore ELB health checks by default: An Auto Scaling group only uses EC2 status checks unless you set --health-check-type ELB. Without it, instances failing the load balancer's health check stay in service forever. See auto-scaling.md.

IMDSv2 hop limit breaks containers: the default HttpPutResponseHopLimit of 1 makes the IMDSv2 token PUT response fail to reach a containerized process (the extra hop exceeds the response TTL), so the token request times out. Set HttpPutResponseHopLimit=2 for bridge/awsvpc container workloads. (If IMDSv2 is required, a subsequent tokenless GET returns 401; if optional, it silently falls back to IMDSv1.) See provisioning.md.

T3/T3a/T4g default to unlimited mode: Unlike T2 (standard), these burst without throttling but bill surplus CPU credits when 24h-average CPU exceeds baseline — a silent cost leak. See instance-selection.md.

Instance store is ephemeral: Data on instance store volumes is lost on stop, hibernate, terminate, instance-type change, and host failure — it survives only a reboot. Put anything durable on EBS/EFS/S3. See instance-selection.md.

Which do you need?

If you're deciding...	Guidance
Instance family / size / Graviton / GPU / burstable	instance-selection.md — start with the workload→family table
How to define instances once and reuse (launch template)	provisioning.md
How to run many instances that scale automatically	auto-scaling.md
How to access/patch/manage instances without SSH keys	systems-manager.md

Quick Navigation

You want to...	Go to
Pick an instance type, Graviton vs x86, burstable credits, GPU, instance store vs EBS	instance-selection.md
Create a launch template, user data, key pairs, IMDSv2, placement groups, Elastic IPs	provisioning.md
Set up or fix an Auto Scaling group, scaling policies, instance refresh, Spot, lifecycle hooks	auto-scaling.md
Get SSH-less access, patch a fleet, or fix an instance not showing as a managed node	systems-manager.md
Create, share, or retire (deprecate/disable/deregister) an AMI	ami-management.md
Fix something broken (can't connect, status-check fail, capacity error, stuck instances)	troubleshooting.md

Common Workflows

"Stand up an autoscaling web fleet" → Create a launch template (AMI, type, IMDSv2), then an ASG referencing it with --health-check-type ELB and a target-tracking policy, see auto-scaling.md. For the public entry point, secure the load balancer (TLS/ACM, WAF, security response headers) per the Security Considerations below and the load-balancer notes in auto-scaling.md — the load-balancer build itself belongs to aws-networking.

"Roll out a new AMI to my fleet" → New launch template version → instance refresh; pin a numeric launch-template version so rollback works, see auto-scaling.md.

"Connect to a private instance without a bastion" → Give the instance SSM permissions (an instance profile with AmazonSSMManagedInstanceCore, or account-level DHMC) plus a network path, then use Session Manager, see systems-manager.md.

"Cut EC2 cost" → Right-size (burstable vs fixed-performance), Graviton where the app supports Arm64, Spot with price-capacity-optimized for fault-tolerant fleets, release idle Elastic IPs, see instance-selection.md.

Troubleshooting

Symptom	Likely cause	Quick fix
SSH "Connection timed out"	Network path (SG/NACL/route/no public IP)	Open TCP 22 from your IP; check route to IGW; verify public IP — see troubleshooting.md
SSH "Connection refused"	Host: sshd down or still booting	Wait for boot; check sshd/port via Session Manager or serial console
InsufficientInstanceCapacity	AWS lacks capacity of that type in the AZ (NOT a quota)	Try another AZ / instance type / retry; don't request a quota increase
InstanceLimitExceeded	vCPU quota reached (this IS a quota)	Request a Service Quotas increase for the instance family
ASG never replaces LB-unhealthy instances	Health check type still EC2	Set --health-check-type ELB
Instances stuck in Pending:Wait, terminated after ~1h	Lifecycle hook never completed (heartbeat 3600s, default ABANDON)	Call complete-lifecycle-action CONTINUE, or set DefaultResult CONTINUE
System status check failed	AWS host/hardware	Stop/start to migrate to new hardware (reboot won't)
Instance status check failed	Instance OS/network config	Reboot or fix the OS/network config

Full tables and more errors in troubleshooting.md.

Security Considerations

• Enforce IMDSv2 (HttpTokens=required) on launch templates to block SSRF-based credential theft; set the account-level default per Region (applies to new launches only).
• Prefer Session Manager over inbound SSH — no open port 22, no key management, and a CloudTrail record of session API calls; enable Session Manager session logging to CloudWatch Logs/S3 (off by default) to capture the in-session commands themselves — see systems-manager.md.
• Use instance profiles, never embedded credentials; scope the role to least privilege.
• Encrypt EBS/AMIs; to share an encrypted AMI cross-account, re-encrypt under a customer-managed KMS key (the default aws/ebs key can't be shared).
• Enable CloudTrail in all Regions to audit EC2/ASG/SSM API activity, and alarm on sensitive actions (security-group changes, RunInstances/TerminateInstances from unexpected principals) so unauthorized changes surface.
• For public-facing web fleets, encrypt traffic in transit with an ACM certificate on the load balancer's HTTPS listener and add AWS WAF for defense in depth against common web exploits — the load-balancer/WAF setup itself lives in aws-networking.
• For hardening beyond this guidance, see AWS EC2 security best practices and CIS Benchmarks for the guest OS.

Not Covered By This Skill

• Launching a single hardened instance with best-practice defaults → use the launching-ec2-instance-with-best-practices skill
• Creating IAM roles / instance profiles for EC2 → use the setting-up-ec2-instance-profiles skill
• Building AMIs with an Image Builder pipeline → use the amazon-ec2-image-builder skill
• Lambda / serverless → aws-serverless; ECS/Fargate → aws-containers; EKS/Kubernetes → kubernetes
• VPC, subnets, ALB/NLB, endpoints → aws-networking or built-in knowledge
• IAM policy logic and CloudWatch dashboards/agent setup → aws-iam, aws-observability