Troubleshooting SELinux

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Cloud
Security

Troubleshooting SELinux

Mandatory access control (MAC) is an essential element to modern system security. SELinux is a common implementation of MAC that must be well understood by engineers in order to incorporate the most ideal security practices into production systems. This exercise delves into a common occurrence relating to MAC; troubleshooting a system that is experiencing errors as a consequence of SELinux. *This course is not approved or sponsored by Red Hat.*

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Lab Info

Level

Advanced

Last updated

Sep 23, 2025

Duration

30m

Challenge

Verify there is an error by trying to access `localhost:80/index.html` using curl on the `www` host and check the audit log using sealert. Direct the output from sealert to `/home/cloud_user/seinfo.txt`.
- Run curl localhost:80/index.html to confirm the error.
- Run sealert -a /var/log/audit/audit.log > /home/cloud_user/seinfo.txt.
Challenge

Examine `/home/cloud_user/seinfo.txt` to figure out what is wrong and fix the error regarding `/var/www/html/index.html`.
- Reviewing the seinfo.txt file should indicate the context for /var/www/html/index.html is incorrect.
- Run restorecon /var/www/html/index.html to fix the issue.
Challenge

Restart `httpd` to check for other possible issues and correct any issues you might find.
- Run systemctl restart httpd (note: httpd should fail to restart).
- Based on journalctl --xe or by re-examining the audit log with sealert, you will see the file context is incorrect on /etc/httpd/conf/httpd.conf.
- Run restorecon /etc/httpd/conf/httpd.conf to fix the context on httpd.conf.
- Run systemctl start httpd and service should be restored.
Challenge

Confirm `localhost:80/index.html` loads correctly with curl on the `www` host.

Run curl localhost:80/index.html and verify that you get the message "The website is up".

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