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IT Troubleshooting Guides

IT troubleshooting guides for exact errors, not broad technology summaries. Each article explains the failure, shows how to confirm it, and links to a matching browser tool.

DNS

Troubleshooting guide

dig Warning: Recursion Requested but Not Available

Understand why dig prints the recursion warning, when it is expected, and how the aa, rd, and ra flags change the diagnosis.

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Linux

Troubleshooting guide

systemd status=203/EXEC: Causes and Fixes

Work through the executable path, permissions, interpreter, line endings, service identity, and security controls behind status 203/EXEC.

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Containers

Troubleshooting guide

Docker OCI Runtime Exec Format Error: Causes and Fixes

Separate CPU architecture mismatches from broken entrypoint scripts, shebang problems, and Windows line endings.

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Web and TLS

Troubleshooting guide

cURL Error 35: SSL_ERROR_SYSCALL Explained

Use verbose output and independent TLS tests to identify resets, proxies, protocol mismatches, and unexpected peer closure.

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Remote access

Troubleshooting guide

SSH Connection Closed by UNKNOWN Port 65535

Trace the misleading port 65535 message through ProxyJump, ProxyCommand, bastion, forwarding, and middlebox failures.

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