Seems I was wrong,... while strace shows that voms-proxy-init does look around int ~/.globus/certificates... it still geives an error in the end:
Error: verify failed. Cannot verify AC signature! if I didn't set both, X509_CERT_DIR and X509_VOMS_DIR to my custom locations in .globus/certifiates and .voms/vomsdir respectively. -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected]

