Sudoers file on Solaris 10

sudo is available from the SFWsudo package on Solaris 10.
To use it a /etc/sudoers file has been set but still leading to the following error

user NOT in sudoers

Hopefully, truss will help :-)

root@server:/# truss -o /tmp/output sudo ls

The /tmp/output file is answering the enigma:

root@server:/# grep sudoers /tmp/output
lstat("/opt/sfw/etc/sudoers", 0xFFBFFB28) = 0
open("/opt/sfw/etc/sudoers", O_RDONLY) = 4

The sudoers file to edit is in /opt/sfw/etc