A collection of practical references covering Linux administration, network troubleshooting, DNS behavior, and everyday system operations.
Process inspection, memory usage, system services, and routine maintenance on Linux hosts.
Systems / AdministrationUseful methods for investigating name resolution, routing paths, TCP connections and dual-stack networks.
Networks / TroubleshootingResource troubleshooting starts with available memory, active processes, file system capacity and service status. These commands provide a compact initial view.
free -h df -h ss -lnt systemctl --failed
Available memory is generally more useful than the raw free-memory value when evaluating Linux memory pressure. Swap activity should be considered together with actual latency and process behavior.
DNS resolution and transport reachability are separate layers. Check A and AAAA records independently, then test the relevant network family.
dig example.net A dig example.net AAAA ip route get 1.1.1.1 curl -4 -I https://example.net curl -6 -I https://example.net
A successful DNS lookup does not establish that TCP connections or TLS negotiation will succeed. For a dual-stack endpoint, IPv4 and IPv6 paths should be verified independently.
Packet loss, routing changes, MTU limitations and TLS configuration errors can produce similar symptoms. A useful investigation separates connection establishment, TLS negotiation and application response.
Record the destination address, protocol family, connection timing and server response before changing multiple parameters at once.
Watergent Notes is a small technical reference collection focused on practical systems and networking topics. Entries are organized as concise operational notes rather than product announcements.