Mac OS X Directory Structure explained
Mac OS X, Tips & Tricks, Command Line
If you have ever looked at your Mac’s root directory and wondered what some of those other directories are for, you’re probably not alone. Mac OS got a whole lot more complex with the advent of OS X, adapting a unix file structure that is largely unfamiliar to Mac OS 9 and Windows users. So just what is /System, /Library, /usr, and all the others for anyway? Here’s a brief explanation of each directory as found in Mac OS X.
By default, if you look in the root of your Mac’s hard disk you’ll see some unfamiliar sounding directories. From the command line, you will see even more if you type ls /. Explained in no particular order:
| Directory | Description |
| /Applications | Self explanatory, this is where your Mac’s applications are kept |
| /Developer | The Developer directory appears only if you have installed Apple’s Developer Tools, and no surprise, contains developer related tools, documentation, and files. |
| /Library | Shared libraries, files necessary for the operating system to function properly, including settings, preferences, and other necessities (note: you also have a Libraries folder in your home directory, which holds files specific to that user). |
| /Network | largely self explanatory, network related devices, servers, libraries, etc |
| /System | System related files, libraries, preferences, critical for the proper function of Mac OS X |
| /Users | All user accounts on the machine and their accompanying unique files, settings, etc. Much like /home in Linux |
| /Volumes | Mounted devices and volumes, either virtual or real, such as hard disks, CD’s, DVD’s, DMG mounts, etc |
| / | Root directory, present on virtually all UNIX based file systems. Parent directory of all other files |
| /bin | Essential common binaries, holds files and programs needed to boot the operating system and run properly |
| /etc | Machine local system configuration, holds administrative, configuration, and other system files |
| /dev | Device files, all files that represent peripheral devices including keyboards, mice, trackpads, etc |
| /usr | Second major hierarchy, includes subdirectories that contain information, configuration files, and other essentials used by the operating system |
| /sbin | Essential system binaries, contains utilities for system administration |
| /tmp | Temporary files, caches, etc |
| /var | Variable data, contains files whose contents change as the operating system runs |
If we forgot anything, or if something isn’t properly described, feel free to chime in with comments.
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Comments:
Comments: 11
Comment from Martin Hauser
Time: March 30, 2007, 1:39 am
nice thing, though, i think you missed /private out!
Comment from akiko
Time: March 30, 2007, 3:00 am
how about /sw ?
Comment from Hardy Boys and the Case of the Missing Directory
Time: March 30, 2007, 10:36 am
/private, /sw, /opt
are three more I have that aren’t listed, are they install specific?
Comment from Ben Hanson
Time: March 30, 2007, 9:25 pm
/sw is specific to Fink
/opt is common elsewhere, in OS X it probably means you installed DarwinPorts
/private should probably be on the list.
Comment from bongo
Time: April 2, 2007, 5:12 am
actually, /etc is a symlink to /private/etc, like /tmp and /var are to /private/tmp and /private/var. Furthermore, you should point out that /private/var/log/ contains all the system logs.
Now what I never understood is the real difference between /System/Library and /Library….
Comment from 2omega
Time: June 10, 2007, 3:16 pm
>Now what I never understood is the real difference between /System/Library and />Library….
As U have it understood, /Library holds preferences, fonts, screen savers and the such that are available to all users and not just /Users/auser/Library.
/System/Library is more like services and extensions (similar to os 9) but very different. Thats is my guess.
My question is.. where would one logically install *nix software on OS X. Lets say I want to install Image Magick. Where should I place it? mysql get put into /usr/local/ and php gets put into /usr/lib/. This lib/local stuff has me confused.
Comment from You
Time: November 23, 2007, 10:13 am
> This lib/local stuff has me confused.
/usr is used for files installed through a package manager, such as MacPorts
/usr/local is used for files installed manually, such as something you have compiled. Putting them in /usr/local keeps them separate from the mess of files stored in /usr so it’s easier to manually remove the files (since there isn’t a package manager to do it for you).
Comment from Sunny Rabbiera
Time: November 30, 2007, 8:08 pm
[quote]> This lib/local stuff has me confused.
/usr is used for files installed through a package manager, such as MacPorts
/usr/local is used for files installed manually, such as something you have compiled. Putting them in /usr/local keeps them separate from the mess of files stored in /usr so it’s easier to manually remove the files (since there isn’t a package manager to do it for you). [/quote]
Yeh we have the same thing here on linux, that is because both OSX and linux are based on unix one way or another (OSX can be considered more “true” unix though as its based on BSD that is mostly derived from unix, linux however is based more off of minix)
the whole usr/local thing makes perfect sense to me, as we have something pretty much like it here in linux land
Comment from Gerhard Leonhartsberger
Time: March 8, 2008, 5:07 am
Look at Apple.com to see a high level description.
Comment from Angelito Sampang
Time: May 16, 2008, 1:06 am
Hi,
Where can I find /Applications /etc /Network? are these files deletable? If they are, how can I delete them? and how will this affect the OS?
Thanks
Comment from Ben
Time: May 18, 2008, 3:49 pm
> Where can I find /Applications /etc /Network? are these files deletable? If
> they are, how can I delete them? and how will this affect the OS?
In Finder, Go… Go to Folder and type /Applications or whatever folder you want to get to (shift-command-g for keyboard shortcut people).
Deleting any hidden files is never a good idea unless you know what you’re doing. Deleting the /etc directory will probably make your computer unbootable at the very least.
Why would you want to delete that in the first place?
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