In Ubuntu 12.04 I have some users whose home directories are NFS-mounted by automount. All the NFS and automount configurations are right. For a very specific use case, I need to add some lines corresponding to those users 'by hand' to /etc/passwd. Immediately after saving the passwd file, all their home directories are mounted by automount. I don't wan't it to happen. I think It's clear that some process is monitoring the passwd file and accesses the home directories of all of them. If I umount them and add just another line, then all the homes are mounted again.
I have tried lots of things to try to guess what is happening with no luck. I think this is related to Gnome, because we use another Linux machines that run a home made distro based on the Ubuntu kernel and run Gnome and the same thing happens.
¿Any idea?