Export tablespace generate "RA-01031: insufficient privileges" error

Hi all !
I try to exp tablespaces from an 8.1.7.4 Oracle Database (on Sun Solaris 5.8) using the following statement :

exp userid=\"sys/manager AS sysdba\" parfile=exp_tbs.par

Contents of exp_tbs.par file :
TABLESPACES=TBS1,TBS2
TRANSPORT_TABLESPACE=Y
FILE=exp_tts.dmp
LOG=exp_tts.log

I received the following error message :
EXP-00056: ORACLE error 1031 encountered
ORA-01031: insufficient privileges

Do I need to connect to the server with a Unix user with dba group ?
Because I'm not using one right now ...
Thanks in advance ...

Yes, that should work. Try Connecting as user with primary group as DBA at OS level.

Thanks a lot !