Should I install XXX in /usr or
/usr/local?
This is a question without an obvious answer for an LFS based system.
In traditional Unix systems,
/usr usually contains files that come
with the system distribution, and the
/usr/local tree is free for the local
administrator to manage. The only really hard and fast rule is that Unix
distributions should not touch
/usr/local, except perhaps to create
the basic directories within it.
With Linux distributions like Red Hat, Debian, etc., a possible rule is
that /usr is managed by the
distribution's package system and
/usr/local is not. This way the
package manager's database knows about every file within
/usr.
LFS users build their own system and so deciding where
the system ends and local files begin is not straightforward. So the choice
should be made in order to make things easier to administer. There are
several reasons for dividing files between
/usr and
/usr/local.
On a network of several machines all running LFS, or mixed LFS and
other Linux distributions,
/usr/local could be used to hold
packages that are common between all the computers in the network. It can
be NFS mounted or mirrored from a single server. Here local indicates
local to the site.
On a network of several computers all running an identical
LFS system, /usr/local could hold
packages that are different between the machines. In this case local
refers to the individual computers.
Even on a single computer,
/usr/local can be useful if you
have several distributions installed simultaneously, and want
a place to put packages that will be the same on all of them.
Or you might regularly rebuild your LFS, but want a place to put files that you don't want to rebuild each time. This way you can wipe the LFS file system and start from a clean partition every time without losing everything.
Some people ask why not use your own directory tree, e.g.,
/usr/site, rather than
/usr/local?
There is nothing stopping you, many sites do make their own trees,
however it makes installing new software more difficult. Automatic installers
often look for dependencies in
/usr and
/usr/local, and if the file it is
looking for is in /usr/site instead,
the installer will probably fail unless you specifically tell it where to
look.
What is the BLFS position on this?
All of the BLFS instructions install programs in
/usr with optional instructions to
install into /opt for some specific
packages.