dns/
DNS records, resolvers, and TTLs
Query records the way a resolver does, tell an authoritative answer from a cached one, and plan a change so it takes effect when you expect it to.
- Articles
- 2
- Commands to copy
- 19
- Last checked
- 24 Oct 2026
Every DNS article with the versions each was checked against
Other categories
linux/ · 3 articles
Linux
Disks that fill up, jobs that run on a schedule, and the first look at a server that has slowed down. The commands are for systemd distributions: Debian 12, Ubuntu 24.04, and RHEL 9 and its rebuilds.
- The first five minutes on a slow server
- Find what’s filling a disk
- Run a job on a schedule with systemd timers
networking/ · 3 articles
Networking
Find out what’s listening on a port, test whether a port is reachable from somewhere else, and capture the packets when the answer still isn’t clear.
- Find which process is listening on a port
- Test whether a TCP port is reachable
- Capture traffic with tcpdump
tls/ · 2 articles
TLS and certificates
Read what a server’s certificate says, find out when it expires, and convert keys and certificates between the formats different software asks for.
All TLS and certificates articlesssh/ · 2 articles
SSH
Log in with keys instead of passwords, turn passwords off without locking yourself out, and keep every host’s connection details in one config file.
All SSH articleswindows/ · 2 articles
Windows Server
Read the event log, test connections, and look up DNS from PowerShell, with commands that work on Windows Server 2019, 2022, and 2025.
All Windows Server articles