I have successfully configured AuthLDAP plugin to authenticate LimeSurvey against ActiveDirectory however I want to know more how exactly AuthLDAP works. My questions are:

1) Can I disable LimeSurvey internal database so I can use only LDAP?
2) If yes, what happens if my LDAP server will be unavailable? Will public survey execution work for my users? Is there a way to switch Internal Auth database ON again without a user interface?
3) How exactly "Allow initial user to login via LDAP" option work?
4) Can I use LDAP login via API to get a session token for /remotecontrol link?
5) If I enable "Check to make default authentication method" in plugin configuration will the default authentication method change for API logins on /remotecontrol too?

1. I don't think, but each user have a rigt (or no) to login via Auth.
2. No change on public execution, only log in are disabled. No way to disable except remove the AuthLdap file (or update via DB) but : user without AuthDB right still can not log in.
3. The initial user admin is user #1, by default ;: he can not log via LDAP (it was created before config was set) with he can : github.com/LimeSurvey/LimeSurvey/blob/82...AP/AuthLDAP.php#L448
4. Yes, because LDAP have user/password. See www.limesurvey.org/manual/RemoteControl_2_API#get_session_key , the plugin parameter
5. No change : default is for GUI login only, for remote see www.limesurvey.org/manual/RemoteControl_2_API#get_session_key

Thank you. One more question. If I create a user from LimeSurvey GUI with type set to LDAP or if I the user is created automatically by the initial login process I assume it sets a password in the Authdb too? Is it some kind of random password and can I use it in case of LDAP failure (assuming that Authdb rights are given to the user)?

If you create the user : you have to set a password (in my opinion : it's an issue : bugs.limesurvey.org/view.php?id=13222 )

If user was created via LDAP : have password github.com/LimeSurvey/LimeSurvey/blob/82...AP/AuthLDAP.php#L286 (still an issue)

Then : user can ask a new password too (for example)

So what default password does LimeSurvey set if a user is automatically created on LDAP login? Is it random?

Yes : github.com/LimeSurvey/LimeSurvey/blob/82...mon_helper.php#L2275