Logs Are a Story, Not a Wall of Text
Every log line is a sentence in a story your system is already telling, in order, with a timestamp. The problem isn't that the information isn't there, it's that most people only open a log file after something's already gone wrong, with no sense of what normal even looks like to compare against. Reading logs well is a skill you build before the incident, not during it.
Know Where to Even Look
On a modern Linux box, journalctl is usually your first stop, journalctl -u nginx or journalctl -u ssh scopes it to one service instead of the entire system firehose. Older setups and specific applications still write to plain files under /var/log, syslog or messages for the system, an app-specific file for everything else. If you're running containers, docker logs <container> is its own separate world that people forget to check entirely. Knowing which of these three places actually has the answer saves more time than any single command below.
grep, awk, and tail Are Most of the Skill
grep -i "failed" or grep -i "error" turns a firehose into a shortlist in one line. journalctl --since "1 hour ago" narrows by time instead of scrolling by hand. tail -f lets you watch a log live while you reproduce a problem, which is usually faster than reading history after the fact. awk earns its place once you need a specific column out of a structured line, an IP address, a status code, instead of the whole thing. You don't need more tools than this for the overwhelming majority of real troubleshooting.
Know What Normal Looks Like Before You Need To
An anomaly is only recognizable against a baseline you already have in your head. Skim your own logs occasionally when nothing's wrong, not to hunt for problems, just to build a rough sense of what your system's normal chatter actually looks like. The first time you do this, most of it will look alarming. By the tenth time, you'll recognize the background noise instantly and the one line that doesn't belong will actually stand out.
Signal Over Noise: What's Actually Worth Investigating
A handful of failed logins scattered across random IPs is the internet's constant background scanning, not an attack on you specifically. A hundred failed attempts from one IP in two minutes, followed by a successful login, is the thing that gets your attention. Learn to tell the difference between noise you can safely ignore and a pattern that means someone's actually knocking, because treating every log entry as a five-alarm fire is how people burn out and stop reading logs entirely.
Retention and Rotation, So the Log Is Still There When You Need It
logrotate and journalctl's own size limits exist to stop logs from quietly filling your disk, which is good, until the entry you needed rotated out before you knew to look for it. Check your retention settings (journalctl --vacuum-size and /etc/logrotate.conf are the usual places) and set them deliberately instead of trusting whatever shipped by default. A week of retention is fine for a quiet home service. Anything you'd actually need to investigate after the fact deserves more room than that.