When using active directory, group names can have backslashes when specified in the "domain account format". See here for more information:

https://docs.microsoft.com/en-us/windows/desktop/ad/getting-the-domain-account-style-name-of-a-group

"getent group" on Linux is capable of interpreting backslashes in group names when AD is configured. For example, the following command properly gets the information about the AD group:

getent group mydomain\\my-dba-group

However, the pam_user_map module does not seem to support this format at the moment. If /etc/security/user_map.conf contains a line like the following:

@mydomain\\my-dba-group: mysqldba 

Then the module would throw an error like the following:

Aug 28 17:22:02 ip-10-156-191-170 mysqld: pam_user_map(mysql:auth): Syntax error at /etc/security/user_map.conf:5

The same error is seen if only a single backslash is used in the group name. e.g.:

@mydomain\my-dba-group: mysqldba 

The workaround is to set a default domain in the system's AD configuration.