bash
dig +short example.com ANotes
Fetch an A record in short output format.
Linux Networking: DNS, HTTP, and TLS Testing
DNS troubleshooting, resolver inspection, HTTP probing, and TLS certificate testing from Linux.
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DNS Resolution
Query DNS, inspect resolvers, and troubleshoot resolution issues.
bash
dig +short example.com MXNotes
Fetch MX records in short format.
bash
dig +trace example.comNotes
Follow delegation from root to authoritative answers.
bash
dig @1.1.1.1 example.comNotes
Send a DNS query to a chosen DNS server.
bash
host example.comNotes
Look up DNS records with the host command.
bash
nslookup example.com 8.8.8.8Notes
Interactive or one-shot DNS lookup.
Show systemd-resolved status
Inspect current DNS servers and search domains.
bashLINUXresolvectldnssystemd
bash
resolvectl statusNotes
Inspect current DNS servers and search domains.
bash
resolvectl query example.comNotes
Resolve a domain using resolvectl.
bash
getent hosts example.comNotes
Query host resolution through glibc NSS.
bash
cat /etc/resolv.confNotes
Show the resolver configuration file.
HTTP and TLS Testing
Test URLs, certificates, proxies, and HTTP behavior from Linux.
bash
curl -I https://example.comNotes
Make a HEAD request to inspect headers.
bash
curl -v https://example.comNotes
Display request and response details.
bash
curl --resolve example.com:443:203.0.113.10 https://example.comNotes
Pin a host:port to a chosen IP address.
Send request from interface
Use a specific local interface for outbound traffic.
bashLINUXcurlinterfacehttp
bash
curl --interface eth0 https://example.comNotes
Use a specific local interface for outbound traffic.
bash
curl -x http://proxy.example.com:3128 https://example.comNotes
Send an HTTP request through a proxy.
Inspect TLS certificate chain
Open a TLS session and print certificate details.
bashLINUXopenssltlscertificate
bash
openssl s_client -connect example.com:443 -servername example.comNotes
Open a TLS session and print certificate details.
Show certificate dates
Print notBefore and notAfter fields from a certificate file.
bashLINUXopensslcertificatedates
bash
openssl x509 -in cert.pem -noout -datesNotes
Print notBefore and notAfter fields from a certificate file.
Test URL availability
Check whether a URL is reachable without downloading content.
bashLINUXwgethttpavailability
bash
wget --spider -S https://example.comNotes
Check whether a URL is reachable without downloading content.
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