Filesystem layout

Haiku's filesystem layout is quite transparent, trying to always use non-cryptic names for files and folders, that don't leave the user guessing. Files and folders that are important for the system to function properly, are protected from accidental tempering by showing one of these alerts:

The second alert pops up if you try to rename or delete something in the system hierarchy. Here, the "Do it" button will only become clickable when you're holding down the SHIFT key.

Generally, there are three separate branches springing from the root folder of the boot volume:

The system folder - /boot/system/

Under Haiku's predecessor BeOS, this folder was named /boot/beos/. You may still find it in some older documentation (e.g. in the original BeBook).
Whatever it's named, you should not alter what's inside. Every update of Haiku can add, remove or overwrite anything within it. If you want to add functionality, maybe with other Tracker Add-Ons or Translators or maybe another hardware driver, you install these things under your own /boot/home/ hierarchy or, if it's supposed to be for every user, under /boot/common/. As long as Haiku isn't multi-user, this distinction has no apparent effect, as there's only one user with one home folder. But since there will be support for more users than one eventually, it makes sense to learn the right way from the start.

So, let's say you want to install a new Translator for the latest image format, you don't simply copy it into the respective system folder. Remember: Don't touch!
Instead, you put it into the mirrored hierarchy under /boot/common/ or /boot/home/config/.

In our example the location for Translators in the system folder would be

/boot/system/add-ons/Translators/

So, the user "mirror" folder is either

/boot/home/config/add-ons/Translators/
or
/boot/common/add-ons/Translators/

This has another advantage: If the component you have installed messes things up (which is possible as you install hardware drivers like this, too) you are able to choose "Disable User Add-Ons" from the Boot Loader menu and are thus always able to boot without the offending component.

Most of the time, however, you won't have to deal with these things at all, since every software that comes from a trusted source should include an installation routine that handles these things.

The common folder - /boot/common/

Haiku is not a multi-user system yet. Once it is though, every user has her own home folder that is not accessible to anyone else. Every application or added component like Tracker Add-Ons, Translators etc. as well as any data that's supposed to be shared between different users, has to be put under /boot/common/.

The home folder - /boot/home/

This folder belongs to you. Here you can create and delete files and folders as you wish. However, you shouldn't mess too much with the ~/config/ directory and its subfolders. You could delete e.g. the ~/config/settings/ folder without damaging the operating system itself, but who wants to lose all his configurations and application settings? In any case, the system warns you with the at the top mentioned alert.

Besides the ~/config/add-ons/ folder, which mirrors the system's add-ons folder for additional components as described above, there are a few other folders of interest. (By the way, the tilde ("~") is a shortcut for your home folder, so you don't always have to write "/boot/home/" in Terminal.)