I recently encountered an issue where SELinux was blocking the connection to the Azure Monitor Agent (AMA). This may also happen if you had the Microsoft Monitoring Agent (MMA) or the Operations Management Suite (OMS) agent installed previously. Here’s a simple guide on how to troubleshoot and resolve this issue, specifically when using RedHat or CentOS distributions with CEF or Syslog data connectors.
Confirm SELinux Status
First, you need to check if SELinux is causing the problem. Run the following command to see its current status:
sestatusYou’ll see one of these statuses:
- disabled: This means SELinux is turned off and your connection to Microsoft Sentinel should work fine.
- permissive: SELinux is on but not enforcing rules, which is also supported for Microsoft Sentinel.
- enforced: SELinux is actively enforcing rules, which could be blocking your connection. You’ll need to change this setting.
Temporarily Disable SELinux Enforcement
If SELinux is set to “enforced,” you can temporarily disable it to check if this is the issue. Run:
setenforce 0Note: This change will only last until the server is rebooted. To check if the change worked, run:
getenforceYou should see “permissive” as the output, indicating SELinux is no longer enforcing rules.
Permanently Update SELinux Configuration
To ensure SELinux stays permissive even after a reboot, you need to modify the configuration file. Open /etc/selinux/config in a text editor and change the line:
SELINUX=enforcingto:
SELINUX=permissiveSave the file and exit the editor. This will keep SELinux in a permissive state, ensuring it doesn’t block your connection to the AMA agent.
By following these steps, you can troubleshoot and resolve SELinux blocking issues, ensuring smooth log forwarding into Microsoft Sentinel.
Disclaimer
Please note that the above cause and troubleshooting steps can involve various other reasons. This guide addresses only a part of the potential issues you might encounter.
SecByte 
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