i did the following and it is working fine for me
kamailio.cfg
`log_stderror=no`
/etc/rsyslog.d/50-default.conf
`local0.* -/var/log/kamailio.log`
**touch /var/log/kamailio.log chmod 777 /var/log/kamailio.log**
service rsyslog restart service kamailio restart