Sharing file systems

[Tristan Wibberley]

Sumeet Pal Singh wrote:
> HI
> I have ubuntu 5.10 on my system and using FC3 since it was released. I tried
> to install FC4 on my system by sharing the swap and /home partition between
> FC4 and ubuntu. The installation went well. I did not install KDE in FC4.
> I was well aware of permission screw ups that this could lead to, hence I
> did not create any user (The UID and GID of root is preserved across Linux
> distros)
> 
> I booted in as root and created a new user with UID and GID same as on
> ubuntu.
> Now I booted in GNOME and it was completely configured!!!! Moreover gaim
> started and signed me in to all my accounts!!! This was first time login...
> 
> My question is that can is sharing /home okay for a long run or will it lead
> to problems.
> Also can other file systems like /usr be shared along with this and if it
> can be  then under what restrictions??
> If any one has done this please let me know.

'/home' should be sharable. It is one of its founding principles. But it 
depends on the authors of the software you use to not be dumb and avoid 
incompatible changes that prevent you from using two different versions 
of their software. For managed distributions, that means relying on the 
package maintainers to filter out dumbness.

'/usr' will not be sharable between separate managed installations. /usr 
is designed to be sharable from one managed installation to many 
non-managed installations. It is up to you to ensure configuration files 
and '/' programs are updated on the non-managed "slaves". Incompatible 
changes that occur in packages that install to /usr are probably bugs or 
should be strongly advertised (sometimes these things just *have* to 
happen). Some programs on the slave installations will refer to metadata 
in /var, which you should not share (some parts *can* be shared, but 
only if you really know what they're for) - some of those programs might 
assume that they are running on the managed installation - that is a 
bug, but most programs will work fine.

'/usr/local' should be sharable between unmanaged *and* managed 
installation, but it is typically used for software that is specific to 
each installation - if '/usr' is shared, libraries may disappear; it is 
the administrator's responsibility to ensure upgrades go smoothly, and 
to remember what libraries are used by programs in /usr/local/.

More information can be found at http://www.pathname.com/fhs/

-- 
Tristan Wibberley