On the other hand, "what's the point of this apparently pointless complexity?" is a very good question.

That's my point. On linux, there really is no distinction between /bin and /usr/bin. /usr/local/bin is different, as it's the designated location for stuff you install from source. /sbin is also different, because that's where you want your recovery tools. Although usually you'll boot into a livecd for recovery these days, so it's kind of moot.

Again, this about the only thing that systemd, fdo, etc. and I agree on.

> Although usually you'll boot into a livecd for recovery these days, so it's kind of moot.

thats taking a very "desktop" view on things.

Many more systems run as headless installs in some rack somewhere.

Good point, actually. Sorry. I'm not a professional, so I've got less experience with that.

I recently started playing with lisp in ubuntu and decided to go with slime for it. So i installed slime through ubuntu software manager, couldn't find it, couldn't start it (i'm totally new to emacs and slime). After that I read some manuals, made changes to .emacs config and eventually installed slime using emacs and its package manager. Now i'm wondering if i have 2 versions of slime where are they located, which one is being actually used etc.

> use wich <name>

or the even easier to remember 'whereis <name>'

Why should anyone need to have admin privileges to find a file?

From the updatedb manpage:

updatedb is usually run daily by cron(8) to update the default database.

Also:

To create a private mlocate database as an user other than root, run

    updatedb -l 0 -o db_file -U source_directory

Note that all users that can read db_file can get the complete list of files in the subtree of source_directory.

Because updatedb needs to look at your system's private parts. Try

    find /. | grep [string]

which will look everywhere for [string]