Your Site Is Not Down. DNS Might Be Lying.
The browser said the site was gone. The server was answering fine.
curl --resolve example.com:443:203.0.113.10 https://example.com/
problem area
Web Server Rescue
Small checks that separate DNS, TLS, Nginx, and app failures.
11 checked fixes
One-liners in this area
Check What Is Actually Listening
The app was running. The port was not listening.
ss -tulpn | grep ':80\|:443'
Check the Current Release Symlink
One glance tells you which release directory production is pointing at.
readlink -f releases/current && ls -ld releases/current
Smoke Check an HTTP Status
A deploy is not done until the endpoint answers.
curl -fsS -o /dev/null -w '%{http_code} %{time_total}s\n' https://example.com/health
Inspect Release Disk Usage
Disk pressure during deploys often starts in old release directories.
du -sh releases/* 2>/dev/null | sort -h | tail -10
Find Restarting Containers Fast
Restart loops hide in plain sight unless you filter for them.
docker ps -a --filter status=restarting --format 'table {{.Names}}\t{{.Status}}\t{{.Image}}'
Read Recent Container Logs
Skip the million-line log scroll and read only the recent failure window.
docker logs --since 10m --tail 100 api
Show Published Container Ports
When a service is unreachable, confirm Docker is publishing the port you think it is.
docker port web
Check Filesystem Space with df
A full disk can break logins, uploads, databases, and deploys.
df -h
Find Large Directories with du
Once you know a filesystem is full, the next question is where.
du -xh --max-depth=1 /var 2>/dev/null | sort -h
Find Broken Internal Links in Built HTML
A broken internal link is easiest to catch before it becomes a 404.
grep -Rho --include='*.html' 'href="/[^"]*"' public | sed 's#href="##;s#"##' | while read -r path; do test -e "public${path}" || echo "$path"; done | sort -u