Is there a way to give access to a user to a specific file in the efs? For example: give access to an anonymous user to a file
EFS uses native Linux permissions for controlling access to any file on the system. In general, you can set read write or execute permissions for the owner, group and everyone else.
However, there is no concept of an anonymous user at the OS level, as anyone would need to have an account on the server to gain access to the the file.
By giving the file 644 file permissions, you can grant read access to everyone on the system.
For more information on Linux file permissions, see File permission meanings.