bashLINUXdigdnsa-record
bash
dig +short example.com AFetch 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.
bashLINUXdigdnsmx
bash
dig +short example.com MXFetch MX records in short format.
bashLINUXdigdnstrace
bash
dig +trace example.comFollow delegation from root to authoritative answers.
bashLINUXdigdnsresolver
bash
dig @1.1.1.1 example.comSend a DNS query to a chosen DNS server.
bashLINUXhostdnslookup
bash
host example.comLook up DNS records with the host command.
bashLINUXnslookupdnslookup
bash
nslookup example.com 8.8.8.8Interactive or one-shot DNS lookup.
bashLINUXresolvectldnssystemd
bash
resolvectl statusInspect current DNS servers and search domains.
bashLINUXresolvectldnsquery
bash
resolvectl query example.comResolve a domain using resolvectl.
bashLINUXgetentdnsnss
bash
getent hosts example.comQuery host resolution through glibc NSS.
bashLINUXresolv.confdnsconfig
bash
cat /etc/resolv.confShow the resolver configuration file.
HTTP and TLS Testing
Test URLs, certificates, proxies, and HTTP behavior from Linux.
bashLINUXcurlhttpheaders
bash
curl -I https://example.comMake a HEAD request to inspect headers.
bashLINUXcurlhttpdebug
bash
curl -v https://example.comDisplay request and response details.
bashLINUXcurldnsoverride
bash
curl --resolve example.com:443:203.0.113.10 https://example.comPin a host:port to a chosen IP address.
bashLINUXcurlinterfacehttp
bash
curl --interface eth0 https://example.comUse a specific local interface for outbound traffic.
bashLINUXcurlproxyhttp
bash
curl -x http://proxy.example.com:3128 https://example.comSend an HTTP request through a proxy.
bashLINUXopenssltlscertificate
bash
openssl s_client -connect example.com:443 -servername example.comOpen a TLS session and print certificate details.
bashLINUXopensslcertificatedates
bash
openssl x509 -in cert.pem -noout -datesPrint notBefore and notAfter fields from a certificate file.
bashLINUXwgethttpavailability
bash
wget --spider -S https://example.comCheck whether a URL is reachable without downloading content.
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