Logs are the fastest way to stop guessing. This guide covers the two files that matter and a simple workflow to go from “something’s wrong” to “Apache, PHP-FPM, or WordPress.”
The two files that matter
- Error log (why it failed):
/var/log/apache2/error.log - Access log (what was hit):
/var/log/apache2/access.log
What to look for
- Proxy/FastCGI backend errors (often point to PHP-FPM or wrong socket)
- Permission-denied messages
- Repeated 500s tied to a single path
- Redirect loops (repeated 301/302 in access log)
Fast workflow
- Find the timestamp of the failure
- Identify the path or URL
- Follow the chain: Apache → PHP-FPM → WordPress/plugin
FAQ
Apache error log shows “proxy: error” or “connection refused”—what next?
PHP-FPM is likely down or Apache is pointing at the wrong socket. See PHP-FPM socket mismatch and WordPress 500 triage.
Where do I find PHP-FPM errors?
Location depends on distro and pool config; often under /var/log or in the pool’s slowlog/error config. Check the pool file for your site’s PHP-FPM pool.
Related
- WordPress 500 errors: fast triage — 500 triage flow
- Fixing Apache restart failures — when Apache won’t reload