okay, radutmp file is created, it seem that radutmp file relies on detail log file.
Fri May 2 12:07:10 2014
Acct-Session-Id = "00000336"
Called-Station-Id = "c8f9.f917.bd91"
Calling-Station-Id = "0021.5c5b.8ef3"
User-Name = "testuser"
Acct-Authentic = RADIUS
Acct-Session-Time = 97
Acct-Input-Octets = 22387
Acct-Output-Octets = 20126
Acct-Input-Packets = 252
Acct-Output-Packets = 120
Acct-Terminate-Cause = Lost-Carrier
Acct-Status-Type = Stop
NAS-Port-Type = Wireless-802.11
NAS-Port = 1069
NAS-Port-Id = "1069"
Service-Type = Framed-User
NAS-IP-Address = 192.168.1.1
Acct-Delay-Time = 0
Acct-Unique-Session-Id = "20e5c440d3d1355a"
Stripped-User-Name = "testuser"
Realm = "NULL"
Timestamp = 1399032430
Fri May 2 12:07:12 2014
Acct-Session-Id = "00000338"
Called-Station-Id = "c8f9.f917.bd91"
Calling-Station-Id = "0021.5c5b.8ef3"
User-Name = "testuser"
Acct-Authentic = RADIUS
Acct-Status-Type = Start
NAS-Port-Type = Wireless-802.11
NAS-Port = 1070
NAS-Port-Id = "1070"
Service-Type = Framed-User
NAS-IP-Address = 192.168.1.1
Acct-Delay-Time = 0
Acct-Unique-Session-Id = "4a04d32328d2b261"
Stripped-User-Name = "testuser"
Realm = "NULL"
Timestamp = 1399032432
but , if i do radwho in the radius server I still get :
radwho: No configuration information in radutmp section of radiusd.conf!
radutmp file is created under /var/log/radius directory.