Problem: Jenkins Built-In Node Showing Offline on EC2 If you have ever set up Jenkins on an AWS EC2 instance and seen your Built-In Node showing offline with builds not running — this post is for you! Here is exactly what happened, why it happened, and how I fixed it step by step. Understanding the Warning When I clicked on the Built-In Node I saw this error: Disk space is below threshold of 1.00 GiB. Only 951.90 MiB out of 956.65 MiB left on /tmp. Jenkins monitors your server's system resources constantly. It requires: Resource Minimum Required Free Disk Space ≥ 1 GB Free Temp Space /tmp ≥ 1 GB Free Swap Space > 0 B In my case the checks showed: Free Disk Space: 22.26 GiB — perfectly fine Free Temp Space /tmp : 951.90 MiB — below Jenkins threshold Free Swap Space: 0 B — no swap at all The /tmp partition was only 956 MiB total — just under Jenkins' 1 GB requirement. So Jenkins automatically took the Built-In Node offline and refused to run any builds.…