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Using FreeBSD's ACLs
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Understanding Directory ACLs

A file can have only one ACL, its "access ACL." Most users will be happy with the ability to fine-tune the permissions on the files they create, as demonstrated in the previous section.

Directories are more complex, as they can have up to three types of ACLs:

  • An access ACL affects access to the directory itself.
  • The default directory ACL sets the default permissions on any subdirectories created within the directory.
  • The default access ACL sets the default permissions on any files created within the directory. Note that if the default directory ACL is not set, subdirectories will also inherit this ACL. However, if the default directory ACL is set, that value will override the value of this ACL.

The current FreeBSD implementation supports only the first two types of directory ACLs, so double-check the effective permissions on any files you create in directories containing ACLs.

To see how this works, create a directory called folder.

Note: If you're planning on setting an ACL on a directory, do so before you add any files or subdirectories to that directory. This is because only objects created after the ACL can inherit the ACL. If you add an ACL to a directory that already contains files or subdirectories, always double-check that they contain the desired ACLs.

Look at the ACL properties for folder (Figure 7). It looks similar to a file, except the Default ACL button is no longer grayed out and there is a new Default check box under the Participants list.

ACL properties for the new directory
Figure 7. ACL properties for the new directory

The User, Group, and Other permissions affect access to the directory itself and therefore represent the first type of ACL or the access ACL.

adding Default ACL properties
Figure 8. Adding default ACL properties

Click on that Default ACL button. As Figure 8 shows, there are now four additional entries. These represent the second type of ACL, or the default directory ACL, and affect only subdirectories. Verify this by creating a subfolder and file:

% getfacl folder

% mkdir folder/subfolder
% touch folder/testfile
% ls -l folder
drwxr-xr-x+ 2 dru  dru  512 Jul 27 12:23 subfolder
-rw-r--r--+ 1 dru  dru    0 Jul 27 12:23 testfile

Notice that subfolder inherited the directory permissions but testfile did not.

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