NonStandard Directory Tree, Wildcards in PATH, etc

Ian Molton spyro at f2s.com
Tue Aug 10 17:01:10 PDT 2004


On Tue, 10 Aug 2004 19:31:13 +0100
Jeremy Henty <jeremy at chaos.org.uk> wrote:

> 
> *But* ... now wouldn't it be cool to have several versions of the OS
> in directories called "/linux-<version>", a symlink /linux ->
> linux-<version-current> and be able to change versions by pointing
> that symlink elsewhere and rebooting.

Ugh :)

I can see what you want, but its not very flexible.

if what you really want is 3 OSes on the same machine, use LVM2 to
provide nice flexible volume managment and filesystem resizing, and
place each OS on its own partition (they can share a 'data' partition).

In practice though, unless you are comparing distros, its not a very
useful feature.

Its easy to make a 2.4 and 2.6 kernel co-exist with *exactly* the same
userspace, which gives you full choice should you need some obscure
driver that only exists in one kernel or the other.

and as to libraries, unlike windows, its easy to have several versions
of libraries co-exist on linux.

If I may explain a bit about the 'way things are done' on unix
systems...

a typical vendor system will have three 'layers'

1) The core OS and userspace (init, shells, etc.)
2) The 2nd-layer of 'fluff'  (tools, X windows, GUI etc.)
3) User-installed fluff, not distro related.

1) lives in /
2) lives in /usr
3) lives in /usr/local

each 'layer' has 'executables' (bin, sbin) 'libraries' (lib) 'config
files' (etc) shared stuff (share) and a few others (var, tmp, and
friends).

This organisation works very well but for a small number of very large,
highly modular applications (apache, mysql, mozilla).

Hope this helps.



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