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Take Control of
Permissions in Snow Leopard

Brian Tanaka

Permissions problems got you down? This guide to the permissions that control access to your files, folders, and disks explains how to keep files private, repair permissions, set Ignore Permissions for external disks, work with files on servers, and delete files that won’t die.

This product has been discontinued.

Permissions problems got you down? Turn to Unix expert Brian Tanaka’s unique guide to the permissions in Mac OS X 10.6 Snow Leopard that control access to your files, folders, and disks. You’ll learn how to keep files private, when to set Ignore Permissions, what happens when you repair permissions, how to delete stuck files, and the best ways to solve permissions-related problems. Advanced concepts include the sticky bit, Snow Leopard’s increasingly important access control lists (ACLs), bit masks, and symbolic versus absolute ways to set permissions. The book covers how to take control of permissions via the Finder, with the Mac utility FileXaminer, and using the Unix command line.

Read this book to learn the answers to questions like:

  • Why do so many problem-solving sites suggest that I repair permissions?
  • Why can’t I always access my own files when I boot from an external drive?
  • What should I do if someone tells me to set the permissions to -rw-r–r–?
  • What are promiscuous permissions, and should I inform the vice squad?
  • What’s new about access control lists (ACLs) in Snow Leopard?
  • What are the default permissions for copied files?
  • Without the NetInfo database, how do I edit account settings like numeric UID?
  • How do I work with account groups from System Preferences?

About Brian Tanaka

Brian Tanaka has worked for a variety of companies including the Well, SGI, Intuit, Nintendo, and RealNetworks. Today, his own company, Martingale-Oak LLC, provides Unix and open source technologies consulting. His articles have appeared in Linux Journal and Sysadmin Magazine.

What’s New in the Snow Leopard Edition

This book is a complete, Mac OS X 10.6 Snow Leopard-specific update to Take Control of Permissions in Leopard. Whereas that book covered all versions of Mac OS X up to and including 10.5 Leopard, this book focuses tightly on Snow Leopard.

Changes in this edition include:

  • Of the three third-party tools that I recommended in earlier editions of this book (FileXaminer, Super Get Info, and XRay), only FileXaminer remains available for Snow Leopard. See Set Permissions Using FileXaminer .
  • ACLs are on by default in Snow Leopard. Therefore, we no longer need to test whether or not ACLs are on. Furthermore, we previously used fsacltl to test ACL status, but fsacltl has been removed from Mac OS X. See Use Access Control Lists.
  • In Leopard, a umask in /etc/launchd.conf did not work, contrary to Apple’s documentation. In Snow Leopard, it does work, but the warning from the last edition to avoid using this technique still stands. See Understand Default Permissions.
  • In Snow Leopard, a umask in ~/.launchd.conf doesn’t work, contrary to Apple’s documentation. Unfortunately, that means there is no way in Snow Leopard to set default permissions on files and folders created by the Finder or Mac OS X applications on an account-by-account basis. Read Understand Default Permissions.
  • Many of the default permissions (and ACLs) that result from the copy operations described in Permissions on Copied Items have changed. I have updated the tables accordingly. For example, when copying a file to another user’s Drop Box, unlike in Mac OS X versions prior to Snow Leopard, the ACLs on the resulting file are such that the receiving user can edit the file, and more interestingly, after saving, the file ownership switches to the receiving user’s account. See Permissions on Copied Items.

Q: Do you have an ebook that covers permissions in older versions of Mac OS X?

A: Yes, we do. See Take Control of Permissions in Mac OS X, which covers permissions in Mac OS X 10.4 Tiger and earlier, and Take Control of Permissions in Leopard, which adds Leopard-specific details.

  • Read Me First
  • Introduction
  • Permissions Quick Start
  • Problems and Solutions
  • About Permissions
  • The Anatomy of Permissions
  • Choose a Method of Setting Permissions
  • Set Permissions Using the Info Window
  • Set Permissions Using FileXaminer
  • Use Access Control Lists
  • Understand Default Permissions
  • Work with User Names, UIDs, and GIDs
  • Understand Ignore Ownership
  • Repair Permissions with Disk Utility
  • Learn Advanced Unix Techniques
  • Learn More
  • Appendix A: Fixes for Common Problems
  • Appendix B: Converting to Octal
  • Appendix C: Use the man Command
  • January 2012 -- Although we might reconsider at some later date, at this time, we have no plans to update this ebook.