Permissions

In this guide: Permissions. chmod/chown basics.

Commands below target a typical Linux setup (Ubuntu/Debian). On other distros, package/service names may differ.

If something goes wrong: check the service is running, listening on the expected port, and that your firewall allows the connection. For web services, `nginx -t` and `journalctl -u nginx` are good starting points. Typical permissions: directories `755`, files `644`, secrets `600/640`. 777 is almost always a mistake.

After completing the steps below, verify the result: service status, logs, and network reachability. This saves hours when an issue shows up later.

Below you’ll find a quick checklist, verification commands, and common pitfalls. This helps you not only “do it”, but also confirm what a correct outcome looks like.

Quick checklist

• Check service status and logs after each change.
• Keep headroom for disk and memory: many “random” issues are OOM/disk-full.
• Do not edit system files without a backup copy.
• Make one small change at a time and verify the result immediately.
• Keep notes of what you changed (file/command/time).

Verify the result

# Verify / sanity checks
uptime
free -h
df -h
sudo systemctl --failed --no-pager || true

Common pitfalls

• Editing configs without validating syntax (sshd/nginx).
• Full disk (logs/caches/Docker) causes cascading failures.

sudo chown -R www-data:www-data /var/www/site

• Directories: 755
• Files: 644
• Secrets: 600/640