I have a headless home server that froze last night. The services stopped responding, and I couldn't access it via SSH. After rebooting, everything seems fine now, but I'm curious about what might have caused the failure. Could anyone recommend where to start looking for clues? What should I be checking to troubleshoot this issue? Thanks in advance!
5 Answers
Installing `sysstat` would be beneficial if it's not already running. Configure it to log at one-minute intervals instead of the default ten. This helps ensure you don't miss any critical events. It's also good to monitor system temperatures to catch any overheating issues that could lead to a freeze.
Don't forget to check for filesystem full issues. Running out of space can cause the system to freeze unexpectedly. You can check this with `df -h` for disk usage, and if you're on a Linux system, `dmesg | grep -i ext4` might show filesystem errors.
Often, freezing could be due to resource exhaustion, like CPU or memory issues. Consider installing a tool like `atop` to monitor resource usage over time; it logs stats that can help you understand what happened before the freeze. Also, if you're on a Debian-based distro, you can run a memory test using `memtest86+`, which will show up in your boot options after installation.
It's great that you're proactive about learning! Here's a step-by-step you can follow:
1. **Check System Logs:** Look at `/var/log/syslog` or `/var/log/kern.log` for any issues leading to the failure.
2. **Disk Health:** Run a SMART diagnostic using `smartctl` to see if your disks have errors. The command is `sudo smartctl -a /dev/sdX` (replace `sdX` with your disk).
3. **Resource Usage:** Check for any out-of-memory issues or high loads that could cause a freeze by running `dmesg | grep -i oom`.
4. **Temperature Checks:** Install `lm-sensors` and use `sensors` to monitor hardware temperatures.
5. **Network Issues:** If SSH was unresponsive, check your network interface status with `ip a`.
These steps should give you a solid start on diagnosing the issue! Let me know if you need deeper explanations on any specific area.
First off, checking the system logs is crucial. You can run `journalctl -b -1 -n 100` to see the last 100 log entries from the previous boot. This might give you hints about what went wrong right before the freeze. If you want to find the last entries more easily, you could use `journalctl -b -1 -r` to read them in reverse order.
That's a smart idea! Reading in reverse will likely show the last logged message before the crash, making it easier to pinpoint the problem.
Totally agree on using `atop`! And running memtest over several passes is key. Just one pass might not catch intermittent problems.