static.apur.in — notes https://static.apur.in/ Short notes and longer procedures on Linux administration. en Wed, 04 Nov 2026 10:05:00 +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. Static addressing on a headless box without locking yourself out https://static.apur.in/docs/netplan-static.html https://static.apur.in/docs/netplan-static.html Tue, 19 May 2026 09:10:00 +0000 netplan try instead of netplan apply, drop-ins instead of typed routes, and reading the generated unit instead of guessing from the YAML. PostgreSQL maintenance that actually runs https://static.apur.in/docs/postgres-maintenance.html https://static.apur.in/docs/postgres-maintenance.html Sat, 25 Apr 2026 14:25:00 +0000 Bloat you can measure, the idle-in-transaction that causes it, the XID deadline that is not negotiable, and why 400 connections is a symptom. Log rotation: the two ways it fails silently https://static.apur.in/docs/log-rotation.html https://static.apur.in/docs/log-rotation.html Tue, 31 Mar 2026 08:40:00 +0000 copytruncate loses lines, a missing create line loses the log entirely, and the growing deleted file is invisible to du. SSH sessions worth configuring once https://static.apur.in/docs/ssh-sessions.html https://static.apur.in/docs/ssh-sessions.html Thu, 05 Mar 2026 17:20:00 +0000 ControlPersist, keepalives that detect a dead peer instead of a dead kernel, the ~. escape, and why Include goes last. Kernel updates: what to keep, what to check, what breaks https://static.apur.in/docs/kernel-updates.html https://static.apur.in/docs/kernel-updates.html Wed, 11 Feb 2026 11:05:00 +0000 A full /boot discovered mid-upgrade, DKMS skipped for lack of headers, and a one-off grub-reboot instead of a new default. What a power cut actually does to a server https://static.apur.in/docs/ups-shutdown.html https://static.apur.in/docs/ups-shutdown.html Sat, 17 Jan 2026 20:30:00 +0000 The journal replayed fine, the SQLite file did not, and the backup that would have covered it had been skipped by a timer without Persistent=.