shareable vs unshareable files

Question

I'm reviewing the Filesystem Hierarchy Standard and it states:

"Shareable" files are those that can be stored on one host and used on others. "Unshareable" files are those that are not shareable. For example, the files in user home directories are shareable whereas device lock files are not.

I know that a device lock file is a file created when a process is in use. And obviously that information shouldn't be placed on different host computer, but at the same time, why would you want to place the files in a user's home directory on another host computer? Is that not a security risk? I don't really see why we should categorize files as shareable and unshareable, or maybe I misunderstood the concept?

Answer 1

In large-scale environments, like labs, or corporate systems, to facilitate administration and allow users to work on multiple PCs, home directories are made available over the network, typically via NFS. In such cases, user accounts are also served over the network, using LDAP or something similar.

A lot of things can be served over NFS - for example, if every system is nearly identical, /usr can be (with a bit of work). But, as anybody who has a home directory on NFS and left Firefox open on some system can tell you, lock files really shouldn't be on NFS shared over multiple systems.

And typically, in such cases, the average user does not have administrative access to any common system.