Disk full at 3am: finding it fast
A sequence that finds the cause in about a minute, including the case where df and du disagree.
Writing
Troubleshooting
Reading journalctl properly
Most people use a fraction of it and miss the parts that make it fast.
systemd Type=simple versus Type=forking
Get this wrong and the service either restarts forever or is reported dead while running.
When it works on the other vendor is not a bug report
Two devices can both follow the standard and still not interoperate.
One-way audio: the usual suspects
Signalling works, one side hears nothing. The cause is almost always in a short list.
SIP call flow for troubleshooting
You do not need to know SIP thoroughly. You need to know where in the exchange it stopped.
Jitter, loss, and what the ear tolerates
Voice quality complaints map to specific measurable conditions. Learn the mapping.
When the satellite link is not the problem
The most expensive, least understood component gets blamed for everything. Prove it before escalating.
Reading a satellite modem’s statistics
The modem knows. Learning to read it separates link faults from network faults quickly.
Acceleration, and what it breaks
Performance enhancing proxies work well and complicate everything they touch.