TOPIC / TAG
Notes in troubleshooting
10 articles
A Safe 90-Second Linux Disk Space Triage
A read-only sequence for finding what filled a Linux server before deleting logs, images, caches, or data you may still need.
Inspect a TLS Certificate with OpenSSL
Check the certificate a server actually presents, including names, issuer, validity, and chain details.
A Calm SSH Host Key Check
Handle an SSH host-key warning without training yourself to delete the evidence and try again.
When Cron Does Not Share Your Shell
Why a command can succeed interactively but fail under cron, with a small wrapper pattern that makes paths and output explicit.
Reading a Failed systemd Service Without Scrolling Forever
A compact sequence for checking a failed systemd unit, its recent logs, and the exact configuration systemd loaded.
Troubleshooting Google Public CA and acme.sh
A focused troubleshooting companion for Google Public CA EAB registration, DNS-01 validation, installation, and renewal with acme.sh.
A Small HTTP Header Check with curl
Inspect the headers a real GET request receives, follow redirects deliberately, and keep response bodies out of the terminal.
Measure an HTTP Request with curl Without Guessing
Use curl write-out values to separate DNS, connection, TLS, first-byte, and total request time.
Check DNS With dig Before Changing It
A compact dig workflow for separating authoritative DNS, recursive caches, and local resolver behavior.
Read Disk Usage Before Deleting Anything
A read-only first pass for understanding a full Linux filesystem before cleanup begins.