404 errors on all websites

Symptoms

All websites on the server show 404 errors, and entries similar to the following appear in the Apache error log.

CONFIG_TEXT: ModSecurity: collections_remove_stale: Failed to access DBM file "/var/cpanel/secdatadir/USERNAME-ip": No such file or directory [hostname "domain.tld"] [uri "/folder/"] [unique_id "YXPk8JHpCdES-kVD6hhC5wAAAAg"]
ModSecurity: Audit log: Failed to create subdirectories: /etc/apache2/logs/modsec_audit/USERNAME/20211023/20211023-1233 (Permission denied) [hostname "domain.tld"] [uri "/folder/"] [unique_id "YXPk8JHpCdES-kVD6hhC5wAAAAg"]

Cause

Enabling the EXPERIMENTAL: Jail Apache Virtual Hosts using mod_ruid2 and cPanel® jailshell option can cause unexpected 404 errors.

Resolution

1. Log into WHM as the root user.
2. Navigate to Home / Server Configuration / Tweak Settings
3. Select the Security tab.
4. Scroll down to the EXPERIMENTAL: Jail Apache Virtual Hosts using mod_ruid2 and cPanel® jailshell option.
5. Set the option to Off.
6. Scroll to the bottom of the page.
7. Click the Save button.

Additional Resources

Tweak Settings: Security