cron or systemd timers
Both run things on a schedule. One of them tells you when it failed.
Writing
Articles
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.
Understanding load average
It is not a percentage, and a load of 8 may be perfectly healthy.
SSH hardening without locking yourself out
The order of operations matters more than the settings.
Log rotation that does not lose data
The default rotation method silently breaks with any process that holds its log open.
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.
Network documentation that survives contact with reality
Perfect documentation is always out of date. Aim for the parts that stay true.
When it works on the other vendor is not a bug report
Two devices can both follow the standard and still not interoperate.
Migrating a configuration between vendors
Translating line by line produces a configuration that works until it does not.