nxserver --daemon may crash while detecting physical sessions if it is unable to retrieve the physical session owner's information.

The server log may contain messages similar to the following:

Process: ERROR! Cannot get information for user id 'xxxxx'.
Process: ERROR! Error is 2, No such file or directory.
NXGetUserInfoByUid: WARNING! Failed to get user with uid 'xxxxx' information.

This can happen under several conditions. For example:

-the user belongs to a container or namespace and is not visible to the host system;
-the user exists in a centralized user database (such as LDAP or Active Directory) but not in the local /etc/passwd;
-the user account has been deleted while processes owned by that user are still running.

As a workaround, disable physical session detection by removing physical-desktop from the AvailableSessionTypes key in server.cfg file.