By default, the login server logs errors in the /var/dt/Xerrors file. To change this, you can set the Dtlogin.errorLogFile resource in the Xconfig file. The directory specified must exist when the login server is started.
For example, to have the login server log errors in the /var/mylogs/Dterrors file, set the following in the Xconfig file:
Dtlogin.errorLogFile: /var/mylogs/Dterrors
When the login server is restarted, the login server will log errors to the /var/mylogs/Dterrors file. The /var/mylogs directory must exist when the login server is started.