What are the octal permissions of the directories /usr/lib?

Certain directories on my external HD suddenly require authentication in order to write data. How did this happen, and how I can undo it?

• UPDATE: the affected folders' permissions were changed as follows: (1) my Admin account was removed (2) a bizarre read-only account called "wheel" was added My solution: removed "wheel" and re-added my personal Admin account to the few affected folders I found, problem solved (so far). This is very weird. Examples: if I want to copy a file to my external HD, I need to authenticate with my password. I can no longer import photos into my iPhoto Library (stored on my external HD) and simply get an error message without any authentication prompt. My external drive wasn't used for a week, and it wasn't like this when I last used it. It suddenly changed. I'm familiar with changing permissions generally, but this is such a peculiar and seemingly random change I'd like some expert advice first. Thanks!

• Answer:

  OS X is built on , so it helps to understand that what you do is being done with that technology and that is part of why it doesn't always like Windows files. Let me explain further. That's a folder I made on my desktop to show this example. To get there, secondary-click on a folder and select Get Info. At the bottom you have a look into the UNIX side of your system, with the users who have access to the folder. In this example, all users of the computer (everyone) can read but not write. This is the same with the staff group. If any of them attempt to edit the folder, it will ask for authentication like the question description mentions. SIMPLE ANSWER: Unlock that lock in the lower right corner with an administrator or superuser password, and switch your permissions to "Read & Write" and the issue should be fixed. If the simple answer doesn't work, check your partition format. This can be checked with Disk Utility. Look at the bottom of that screenshot of my main hard drive in disk utility. Where it says Format, you should see Mac OS Extended. In parentheses, you'll see either Journaled, Case-Sensitive and Journaled, Encrypted and Journaled, or Encrypted Case-Sensitive and Journaled. If you have Mac OS Extended -- but you still have a problem -- you may need to go to the Command Line or take your system in for support from Apple. If the drive says something other than Mac OS Extended, such as NTFS or FAT, those are non-Mac formats usually meant for Windows computers and that is likely your problem. If that is the case, you'll be best off backing up the files on the drive and reformatting for Mac OS Extended, but then you can't use the drive with Windows computers afterward without yet another format. Still having a problem? You should probably take your computer in to an Apple Authorized Service Center such as an . If you know UNIX, you can run some relatively simple commands to gain access, but chances are you won't have much luck there where the first step failed unless you have Superuser access. (Such as the root user... more UNIX stuff) Let me help out personally with this. If none of this helps, I will try and provide more answers to help you using the comments. If necessary, I will edit this answer to include instructions on the command line including enabling the root user and modifying system permissions, but that is semi-dangerous territory as you can delete a critical system file without warning. UPDATE: The "wheel" user is not as uncommon as you may think. I've actually got it on my External Hard Drive at home with my Mac mini. All you need in file permissions is your username with "Read & Write" access. Whether you leave wheel there or not, you should be fine; if you are the only user on the computer, and don't plan on adding users later on, you can just allow "Read & Write" access for all users. (The Everyone option)