static.apur.in — notes https://static.apur.in/ Short notes and longer procedures on Linux administration. en Tue, 03 Nov 2026 09:40:00 +0000 In-place Ubuntu LTS upgrade on a remote box https://static.apur.in/docs/debian-upgrade.html https://static.apur.in/docs/debian-upgrade.html Sun, 01 Nov 2026 11:20:00 +0000 Order of operations for do-release-upgrade where you cannot walk up to the machine, and the four things that break quietly afterwards. systemd timers that quietly stopped firing https://static.apur.in/notes.html#timers https://static.apur.in/notes.html#timers Wed, 28 Oct 2026 07:30:00 +0000 Persistent= is not a detail, and a service that exits 0 while doing nothing is worse than one that fails. restic backups on a timer, and the restore drill https://static.apur.in/docs/restic-backups.html https://static.apur.in/docs/restic-backups.html Mon, 19 Oct 2026 16:05:00 +0000 Two repositories with different failure domains, a prune policy you can defend, and a restore test that is scheduled rather than intended. PostgreSQL backup checklist https://static.apur.in/notes.html#backup https://static.apur.in/notes.html#backup Sun, 11 Oct 2026 15:05:00 +0000 Five things that decide whether the backup is real. Triage for a noisy access log https://static.apur.in/notes.html#logs https://static.apur.in/notes.html#logs Wed, 30 Sep 2026 18:40:00 +0000 Before fail2ban: work out what the traffic actually is. Reading SMART before the disk tells you https://static.apur.in/docs/smartd-checks.html https://static.apur.in/docs/smartd-checks.html Mon, 21 Sep 2026 08:15:00 +0000 PASSED is not a verdict. Four attributes on spinning media, four on NVMe, and the two ways monitoring quietly covers for fewer disks than you own. journalctl recipes I kept re-deriving https://static.apur.in/docs/journalctl-cookbook.html https://static.apur.in/docs/journalctl-cookbook.html Sun, 30 Aug 2026 13:45:00 +0000 Previous boot, exact field filters, cursors for polling scripts, and the storage setting that empties the journal at exactly the wrong moment. apt holds and pins, and how they rot https://static.apur.in/docs/apt-holds.html https://static.apur.in/docs/apt-holds.html Tue, 14 Jul 2026 10:00:00 +0000 A hold stops security updates without saying so, and the reason it was added is usually gone two point-releases later. SPF, DKIM and DMARC for one small domain https://static.apur.in/docs/mail-auth.html https://static.apur.in/docs/mail-auth.html Sat, 27 Jun 2026 12:30:00 +0000 Three records answering three different questions, the ten-lookup limit, and why p=none comes first.