When a change is made to a directory, that change is often visible regardless of the path through which the directory is viewed. There are times when it is desirable to make a change that is only visible when the directory is viewed through a particular path, or from a particular virtual system. Such a change creates a customized view of the directory; the change will not affect the view of the directory when reached through other paths, or from other virtual systems.
To create a customized view of a directory, create an empty directory, add a union link from the directory you just created to the target directory, then remove the link to the old directory and replace it with a link to the directory that was just created.
Links that are added to the customized directory will only be visible through the customized directory, but changes to the target directory will also be visible through the customized directory.
Some directories in your virtual system have already been customized. The root of your virtual system is your own. Changes in the root do not appear in the roots of other virtual systems. Each of the links from the root is also a customized directory. For example, if you add a link to the /authors directory, that link will not be visible to others. Directories at the next level, however, are not customized. Thus, if you add a link to the directory /authors/Shakespeare,William, that change will be visible to others unless you first customize that directory.
You can determine whether a directory has been customized by using the vls -u command. That command will show the current directory without expanding union links. Admittedly, this is a little confusing. Future releases will support the concept of an owning virtual system. This will clear up some of the confusion by allowing automatic creation of a customized directory when one is needed.
To have a link added to the master copy of a shared directory you should send a message to pfs-administrator at your site, or to email@example.com.