...
SetEnvIf Cookie "(^|;\ *)username=([^;\ ]+)" MyCookieValue=$2
<If "%{env:MyCookieValue} != ''">
RequestHeader set X-WEBAUTH-USER "%{MyCookieValue}e"
</If>
5. Restart Apache httpd server and Grafana
...
SetEnvIf Cookie "(^|;\ *)username=([^;\ ]+)" MyCookieValue=$2
<If "%{env:MyCookieValue} != ''">
RequestHeader set X-WEBAUTH-USER "%{MyCookieValue}e"
</If>
5.Restart Apache httpd server and Grafana
...