[bobby]

it wouldn't take long to check out man chown, man chgrp, man chmod

just that this should be chgrp zimbra redo.log

chgrp redo.log zimbra

and i think you also want chmod g+w redo.log so you get something like this:

-rw-rw---- 1 root zimbra 512 Feb 27 17:50 redo.log