That seems to come from a yp (nis) lookup. If you are not actually using nis, and everything works, it is probably safe to ignore that. You can perhaps experiment with commenting out the “+auto.master” line, as I think that’s what triggers a nis lookup.
I looked over your post earlier, but could not see what was causing the problem. So I’m glad you have it fixed, even if you are not sure how.
If I’m reading your post correctly, you’re using the systemd “autofs.service” but, you’re neither restarting the autofs service by means of “systemctl restart” nor, checking the status by means of “systemctl status” …
The 2nd field should include an explicit indication of the “map-type” if unexpected behaviour of the “+auto.master” line is to be avoided: “file:/etc/auto.tower” …
man 5 nfs:
intr / nointr This option is provided for backward compatibility. It is ignored after kernel 2.6.25.
I’m no longer a fan of using the “rsize” and “wsize” options – current NFS seems to be able to look after itself: <http://nfs.sourceforge.net/nfs-howto/ar01s05.html>.
The “rw” option is currently the default value.
If map name does not contain explicit type and does not look like file name, automountd tries to look it up using map sources configured in /etc/nsswitch.conf. Default nsswitch.conf contains “nis” for “automount”. If you do not have any external map sources, just delete “+auto.master” line or adjust nsswitch.conf to list only map sources you actually have.