Is the default directory structure (all these /usr, /bin, /etc directories) hard coded in the kernel?
No, most of that does not mean much to the kernel. It does, however, populate file systems mounted in standardized locations like
Is it possible to change the default Unix/Linux directory structure?
Absolutely not. The reason there is a standard for the root file system is because these directories have a defined purpose, and they are identified by path. It does not really make much sense to say, "Oh well, I'd prefer if my
/etc directory where called
/masterconf." If you want to access what everyone and everything else considers
/masterconf, you're welcome
to add a symlink
ln -s /etc /masterconf, but leave
/etc as pretty much everyone and everything else will be looking for that.
By analogy, someone could say, "I'd like to rename all the standard utilities --
cd, etc. -- so that they only exist by the names I've given them." Again, you can symlink them, but to create a standard which allows the system to configure names for standard utilities in place of the normal ones would be:
- Much more complicated.
- Almost certainly add overhead as installed utilities would have to constantly go through some kind of look-up to sort out your novel naming scheme.
- Completely pointless for 99.9999%+ of users.
Points 1 and 2 are significant drawbacks that cannot be justified in light of 3, which is why there is no such system. Likewise WRT renaming parts of the standard filesystem.
What I need is to have...
Again, you can do whatever you want with symbolic or hardlinks (see
man ln), and then you can use those if you prefer them. But do not screw with the filesystem standard, it is not optional.