Tag: sysadmin

You've got backups. Great. But do you know if they actually work? RTO and RPO mean nothing if you've never actually restored.

One app logging to one file becomes a 50GB disk emergency. logrotate config, size-based rotation, Docker log driver limits, and app-level log control.

AppArmor vs SELinux: what mandatory access control actually does, writing AppArmor profiles with aa-genprof, SELinux labels and audit2allow, and when to use each.

Restic, Borg, and Kopia all deduplicate and encrypt, but differ on backends, compression, and UI. Pick the right backup tool for your Linux home lab.

Self-hosted email with Mailcow or Stalwart means daily SPF, DKIM, DMARC, and IP blacklist battles. Here's the honest case against running your own mail server.

Idle SSH sessions and long-lived connections die because the OS gives up first. What the three keepalive sysctls mean, how to tune them, and per-socket options.

Set up auditd to log every sudo command and file change on Linux: auditctl rules, ausearch, aureport, and shipping logs to Loki or Elasticsearch for compliance.

Your VM's clock is off by minutes, NTP says it's synced, yet the system keeps drifting. Here's why the hypervisor is the real culprit, and how to fix it.

MTU mismatches silently break large file transfers, backups, and video calls. Here's how to find and fix the wrong frame size on your network.

DNS broke again. The command sequence that finds it: verify the resolver, reach a server, dig the record, trace the query path, check reverse lookups.

Master LVM snapshots and thin provisioning on Linux. Learn to create, use, and merge snapshots for backups, and over-provision storage safely.

Harden SSH properly: disable password auth, switch to Ed25519 keys, configure sshd_config, set up SSH certificates with step-ca, add 2FA, and configure ProxyJump for bastion hosts.