hupden

fail2ban's client only shows you the present

I wanted to know which addresses had been banned most often. fail2ban-client can't tell you — it reports current state and a couple of counters that reset on restart. The history is in its SQLite database, and by default that database is throwing it away after a day.

FROM scratch Go images have no /tmp

os.CreateTemp failed in production with "no such file or directory" — on the temp directory itself. The tests passed because go test runs on a host that has a /tmp. Nothing in the Go toolchain can see this bug.

Four days of nothing, and every health check stayed green

My log collector went silent for four days at a logrotate boundary. The container was up, the process was running, its own logs kept ticking, and it had ingested exactly zero rows. An open file descriptor follows the inode, not the path.

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fail2ban Filter Tester

Test a fail2ban failregex against sample log lines and see the host it would ban.