I have a MacBook Pro with an external USB hard drive. A program I wrote is having trouble reading the files in `Backups.backupdb` so I look at the permissions:

```
> pwd
/Volumes/G-DRIVE
> ls -led Backups.backupdb 
drwxr-xr-x+ 7 rob  staff  238 Feb 10  2012 Backups.backupdb
 0: group:everyone deny add_file,delete,add_subdirectory,delete_child,writeattr,writeextattr,chown

```

This is an older drive. I no longer use it for Time Machine backups, so I don't care if I clear out permissions that used to protect this folder

But I can't clear them:

```
> sudo chmod -N Backups.backupdb
> chmod: Failed to clear ACL on file Backups.backupdb: Operation not permitted

```

Attempts to find some hidden attribute that might be preventing the chmod:

```
> ls -ldO Backups.backupdb 
> drwxr-xr-x+ 7 rob  staff  - 238 Feb 10  2012 Backups.backupdb
> xattr Backups.backupdb 
[nothing]

```

Why is the operation not permitted?

I just used Disk Utility to look at the drive. It didn't find any problems.