如何通过SSH连接AWS ECS Fargate任务中的Docker容器？

Hey there, let's break down why you can't SSH into your PHP and MySQL containers on ECS Fargate—even though you can ping the task's IP. I've tackled this exact scenario a few times, so here's a step-by-step guide to track down the issue:

1. Make Sure the SSH Daemon is Running in the Container #

Just adding SSH config to your Dockerfile doesn't mean the sshd service is actually active when the container starts. Fargate containers run a single foreground process by default, so if your entrypoint/cmd is launching PHP-FPM or MySQL without starting sshd alongside it, the SSH service won't be up.

• For your PHP container: Check your Dockerfile or entrypoint script to see if it includes a command like service ssh start (or runs sshd in the background) before launching your main app.
• For MySQL: The default entrypoint runs mysqld in the foreground, so you'll need to use a custom shell script as the entrypoint that starts both sshd and MySQL.

A quick way to verify: Temporarily override the container's command in your task definition to run ["ps", "aux"], redeploy the task, then check the CloudWatch logs for that container. Look for sshd in the process list—if it's missing, that's your first fix.

2. Double-Check Port Mappings in the Task Definition #

Even if you exposed port 22 in your Dockerfile, you need to confirm the task definition maps the container port to the Fargate task's ENI (host) port correctly.

• Head to your ECS task definition and look at the Port mappings section for each container:
  • Set the container port to 22.
  • Important: If both your PHP and MySQL containers are in the same task, you can't map both to host port 22. Fargate tasks share a single ENI, so each container needs a unique host port. Assign one to 22 and the other to something like 2222, or leave the host port blank to use an ephemeral port (you can find the assigned port in the ECS task details).

3. Validate Network Configurations #

Fargate uses awsvpc networking, so each task gets its own ENI with the private IP you mentioned. Even if ping works, TCP traffic (like SSH) might be blocked elsewhere:

• Network ACLs: These are stateless, so make sure your subnet's network ACL allows both inbound TCP traffic on port 22 (or your mapped host port) AND outbound TCP traffic (SSH requires a return connection).
• Security Groups: You said you opened port 22 to all, but double-check the inbound rule allows TCP on the correct port. Security groups are stateful, so outbound should be allowed by default, but it's worth confirming no rules are blocking return traffic.
• VPN Routing: Ensure your VPN is properly routing traffic to the VPC where the Fargate task lives. Sometimes ICMP (ping) is allowed, but TCP is blocked by VPN firewall rules.

4. Test SSH from Within the VPC #

To rule out VPN issues, spin up a small EC2 instance in the same VPC and subnet as your Fargate task. Try SSHing to the task's IP from that instance. If it works there but not via VPN, the problem is definitely with your VPN configuration.

5. Check SSH Settings Inside the Container #

Sometimes the sshd config has settings that block connections:

• Verify PermitRootLogin is set to yes (or prohibit-password if you're using SSH keys) in /etc/ssh/sshd_config.
• If using password auth, make sure the root user has a password set and PasswordAuthentication is enabled in the config.
• If using key auth, confirm your public key is added to ~/.ssh/authorized_keys inside the container.

You can inspect the config by temporarily overriding the container command to run ["cat", "/etc/ssh/sshd_config"] and checking the CloudWatch logs.

6. Check for Internal Container Firewalls #

Some base images (like Ubuntu) come with ufw enabled by default. Run ["ufw", "status"] in the container (via command override) to see if it's blocking port 22. If so, add a rule to allow SSH or disable the firewall.

Work through these steps one by one, and you'll likely find where the block is. Let me know if any of these checks point you to the solution!

内容的提问来源于stack exchange，提问作者user10479125