Directory hard links in Linux

Directory hard links in Linux are forbidden. To emulate something similar, you can mount any file system path into any other directory. However, you need to be careful because you can get the same problems as with directory hard links, namely circular and thus infinite file paths...
sudo mount --bind /home/user/Documents/Desktop/ /home/user/Desktop/
Such a link disappears after a reboot. If you want to make it permanent, you can add the mount to /etc/fstab:
/home/user/Documents/Desktop/ /home/user/Desktop none bind

Mounting lvm2 manually

All commands as sudo:
vgscan (--mknodes)
vgchange -ay (volumegroupname)
(lvdisplay or lvs or ls -l /dev/volumegroupname/)
mkdir -vp $PATH/{home,root} (to make a moint point)
mount /dev/volumegroupname/home $PATH/home
mount /dev/volumegroupname/root $PATH/root
(ls -al $PATH/home)


Mounting group directories via the fstab

At the University of Helsinki, one can apply for group directories, which is simply disk space on a NAS. These are easily mounted when you use a university-managed computer via the university menu, but what about if you use your own machine? At least for Ubuntu Linux, the way to mount these directories has changed multiple times during the years and it again broke recently. The current entry in the /etc/fstab file in my (Vanilla, non-university-managed) Ubuntu 16.04 is as follows:

# HY group directories