With Jenkins 2.107.3 the security fix SECURITY-786 was implemented. This allows only the following chars in username:

User name must only contain alphanumeric characters, underscore and dash

We use mail adresses as username in our Jenkins installation, so I would like to modify this behaviour.

To override this behaviour I added the system property 
hudson.model.HudsonPrivateSecurityRealm.ID_REGEX
like descript in the docs. Unfortunately this property is ignored.{{}}

I tested different regex patterns but even the simple example (see attachment) didnt work.

Here is the full docker run command:{{}}

// code placeholder
$ docker run --restart=always -v /home/ubuntu/jenkins_home2:/var/jenkins_home -v /var/run/docker.sock:/var/run/docker.sock -v $(which docker):/bin/docker -u 1000:116 -p 9101:8080 -p 50001:50001 --name stage-jenkins -e "http_proxy=http://172.17.0.1:8888" -e "https_proxy=http://172.17.0.1:8888" --env JAVA_OPTS=-Dhudson.model.HudsonPrivateSecurityRealm.ID_REGEX=[a-z][a-z]+ -d jenkins/jenkins:lts

The final regex pattern would be this one:

--env JAVA_OPTS=-Dhudson.model.HudsonPrivateSecurityRealm.ID_REGEX=[a-zA-Z][a-zA-Z0-9_.@-]+{{}}