I have a VM with an NFS-mounted file system and a Php Storm project in a directory on that file system.
The project is set up to treat the files as "in-place" rather than a remote mounted NFS share with a deployment step.
It is possible to replace /etc/mtab by a symbolic link to /proc/mounts.
When you have very large numbers of mounts things will be much faster with the symlink, but some information is lost that way; in particular, the "user" option will fail.
The offending process could even be umount itself - for example, umount opens the common C libraries, which in turn may open (for example) locale files, which, if they are located on the device in question, will prevent it from being unmounted.
This command would typically be included in a boot script.
Adding the -F option will make mount fork, so that the filesystems are mounted simultaneously.
If only directory or device is given, for example: then mount looks for a corresponding mountpoint (and then, if not found, for a corresponding device) entry in the /etc/fstab file, and attempts to mount it.
The umount command detaches the specified file system(s) from the file hierarchy.