From the mount_nfs(1M) man page:
hard | soft
Continue to retry requests until the server responds (hard) or
give up and return an error (soft). The default value is hard.
Note that NFSv4 clients do not support soft mounts.
A solução é montada com:
mount -F nfs -o vers=3,soft,timeo=10 iphostserver:/opt/media /opt/media
agora vemos as propriedades:
nfsstat -m
/opt/media from iphostserver:/opt/media
Flags: vers=3,proto=tcp,sec=sys,soft,intr,link,symlink,acl,rsize=1048576,wsize=1048576,retrans=5,timeo=10
Attr cache: acregmin=3,acregmax=60,acdirmin=30,acdirmax=60