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Web Server Rescue

Read-only

Smoke Check an HTTP Status

You need a quick status-code check after a deployment.

Command

curl -fsS -o /dev/null -w '%{http_code} %{time_total}s\n' https://example.com/health

Before you run this

System impact: Read-only. Low when scoped to the shown target.

When not to use it: Do not use it for endpoints where a GET request has side effects.

Expected output

A status code and total request time, such as 200 0.183s.

System impact

Read-only. Nothing changes locally. The command sends one HTTP GET request.

Recovery / rollback: no state is changed.

When to use it

Use after deployments, restarts, or DNS changes.

When not to use it

Do not use it for endpoints where a GET request has side effects.

next steps

Related commands

Web Server Rescue Sensitive output

Check the Certificate Served for SNI

The IP was right. The SNI name selected the wrong certificate.

openssl s_client -connect example.com:443 -servername www.example.com </dev/null 2>/dev/null | openssl x509 -noout -subject -ext subjectAltName
Web Server Rescue Sensitive output

Show TLS Certificate Dates

The outage was not the web server. The edge certificate had expired.

openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -dates
Web Server Rescue Sensitive output

Show TLS Certificate Names

The cert was valid, but not for this hostname.

openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -subject -ext subjectAltName
Web Server Rescue Sensitive output

Show TLS Protocol and Cipher

The certificate was fine. The TLS negotiation told the rest of the story.

openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | awk '/Protocol|Cipher|Verify return code/ {print}'
Study mapping

Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.

  • LPIC-1 style command-line practice
  • LFCS style performance-task practice
  • Linux+ style troubleshooting review

Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.