DNS & Name Resolution
Name Resolution
| File | Purpose |
|---|
/etc/hosts | Static hostname → IP mappings (checked first) |
/etc/resolv.conf | DNS server(s) (nameserver) |
/etc/nsswitch.conf | Resolution order (hosts: files dns) |
| Command | Purpose |
|---|
dig example.com | Full DNS query |
dig +short A example.com | Just the answer |
host example.com | Simple lookup |
nslookup example.com | Interactive lookup |
getent hosts example.com | Resolve via nsswitch |
$ dig +short github.com
140.82.112.3
Exam tip: /etc/hosts is consulted before DNS (per nsswitch.conf), so a wrong entry there overrides real DNS.