Fix Permission denied when editing /etc/hosts

Short summary

A concise guide to resolving 'Permission denied' errors when editing the system hosts file on macOS, Linux, and Windows. Covers using sudo or Administrator elevation, a safer copy-then-install pattern with backups, and flushing DNS afterward. Also includes troubleshooting tips for common mistakes like editing the wrong file or forgetting to flush the DNS cache.

• •Use sudo (macOS/Linux) or Run as Administrator (Windows) to edit the protected hosts file
• •Safer approach: edit a working copy you own, back up the original, then install the copy with sudo
• •Flush DNS after changes and verify with grep; keep project hosts snippets versioned outside the system file

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