Technology

Enable Kerberos debug logging in a JVM, Spark driver, and Spark executors to troubleshoot SPNEGO and authentication issues. Covers the exact Java system properties, Spark configuration keys, and how to redirect Spark logs to stdout so Kerberos output interleaves with application logs.

A practical walkthrough of how Hadoop maps Kerberos principals to short names via the auth_to_local property, including rule syntax, acceptance filters, and common troubleshooting patterns.

A quick reference for querying MySQL information_schema to list all foreign key constraints in a given database, including the referencing and referenced columns.

The namei command walks a full path and prints ownership, permissions, and symbolic link resolution for every component. It is a quick way to spot where a permission chain breaks or a symlink redirects unexpectedly.

A host health test flags NTP clock drift when the system clock falls out of sync with its NTP servers. This guide walks through diagnosing and resolving common NTP synchronization failures.

A practical cheat sheet of openssl s_client commands for inspecting, verifying, and troubleshooting SSL certificates in production environments.