EC2 in a Private Subnet Can't Reach the Internet? 6 Checks
An EC2 instance in a private subnet with no internet access is almost always a routing problem. Check the NAT gateway, route tables, security groups and NACLs.
Decode DevOps, visually
Learn how production systems work by seeing how they fail.
Step-by-step troubleshooting for Kubernetes, Docker, AWS, Terraform, CI/CD, Linux and observability, with a diagram for every problem.
$ df -h /var
Filesystem Use% Mounted on
/dev/nvme1n1 100% /var
$ du -sh /var
20G /varLatest write-ups
All articles →Disk Still Full After Deleting a Log File? Here's the Fix
Deleted a huge log file but df still shows the disk full? A running process still holds it open. Find it with lsof +L1 and free the space safely.
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Compare guides & labs →AWS Architecture, Decoded
A visual AWS guide for your phone: 98 pages, 45+ diagrams and 7 architectures, following one app from a single server to event-driven.
- VPC, EC2, storage, databases and IAM, drawn as diagrams
- 7 architectures, from three-tier to event-driven
- Cloud Practitioner exam map
Full version · From $15
Kubernetes Incident Lab
50 realistic broken clusters on your own laptop. Investigate with your own kubectl; a validator checks the live cluster, so shortcuts don't pass.
- Runs locally on kind: macOS, Linux and Windows (WSL2)
- Tickets arrive with a wrong theory, like real on-call
- Hints, walkthroughs and a production lesson after each fix
Full version · From $39
01
See how it's built
Architectures drawn step by step, from one server to event-driven.
02
See how it breaks
Incidents with the symptom, the wrong first theory and the real cause.
03
Fix it yourself
Hands-on labs that check the live system, so shortcuts don't pass.