I want to activate the NTFS support. But I can't find the /etc/fstab on my mac. osx 10.11.5 El Capitan
/etc/fstab doesn't exist by default, only if anything has previously needed it.
fstab itself is merely a text file. If nothing has previously needed one, you can make it yourself.
The standard header appears to be a comment with vague instructions as to how the syntax works...
# fstab # # Identifier mount point fs type options1 #
below that is your mount or ignore instruction, e.g.
UUID=C126C736-1585-3D12-9CF1-F95EFF0CF744 none hfs rw,noauto
LABEL=[drivename] none ntfs rw,auto,nobrowse
There is far more information on
fstab at https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man5/fstab.5.html than I could possibly précis here, or type
man fstab in Terminal.