Sorry for asking this - I know there are many, many posts and responses that seem to be related to this, but some are obviously obsolete (and sometimes not so obviously), and several conflict with each other, so I thought I would explain what I'm trying to do and look for any advice I can get.
First, I'm using 64 bit Ubuntu 12.04 LTS. I have a dual boot system (with a Redmond OS on a separate partition). I have had, for a long time, multiple physical hard drives, and multiple partitions on each of these drives. I currently share many of these drives (partitions) with both OSs as well as with an older version of Windows running in Oracle's VM to support some ancient software that I still use.
I've done this by automounting each drive/partition in fstab, and then assigning Bookmarks in Nautilus for easy access to everything in Ubuntu. Works fine. BUT:
I would like very much to remove/hide/whatever the "standard" Ubuntu directories for Documents, Music, Pictures, and Videos and point them to the appropriate partitions that I already use for such things. To do that, I tried modifying the $HOME/.config/user-dirs.dirs file, changing the default line [XDG_DOCUMENTS_DIR="$HOME/Documents"] to [XDG_DOCUMENTS_DIR="/mnt/Documents"] for instance. After a little experimentation, I've come to the conclusion that locations that don't begin with "$HOME" aren't recognized, leading me to suspect I might need to move the entire home directory somewhere else, but from what I've read in many posts that seems a little over the top and possibly risky.
I also added a line: XDG_DEVELOPMENT_DIR="/mnt/Development". I wasn't too surprised that this did absolutely nothing, but the comments at the file heading used "XDG_xxx_DIR" so I thought it was worth a shot. Can I assume that only certain keywords (e.g. DOWNLOAD, MUSIC, etc.) are supported.
Another thing I noticed is that there are lines in user-dirs.dirs for XDG_TEMPLATES_DIR and XDG_PUBLICSHARE_DIR; although the directories they point to exist, these items don't show up in the Nautilus sidebar. I can access these directories, but this behavior seems somewhat inconsistent to me - likely confirming that I don't really understand what's going on.
I've googled XDG and found lots of references, but nothing that just says how to use these things. Does anyone either know how to do what I'm trying to do, or know of a good explanation somewhere?
In addition to separating "my stuff" from the operating systems stuff so I can easily upgrade versions, my intention is to make backups more organized. Some of my partitions represent totally different lives/hobbies/whatever and it makes sense to me to keep them isolated.
Thanks much for any pointers or advice....