Unix permissions aren't that hard to understand: there's the User, the Group, & the World, & each can read and/or write and/or execute. To change permissions, use the chmod command. It's not that difficult to understand, and it's served us well for decades. But it's not perfect, because it's not as granular as is often necessary in today's complicated security world. For instance, let's say you own the file, & you want to allow Alice to read it & Bob to read and write it, but Alice & Bob are in different groups. Gulp! ACLs to the rescue. ACL stands for "Access Control List", & it allows for a finer-grained control over file system access and usage. Windows has 'em, Mac OS X has 'em, & Linux can use 'em, but the problem is that there's no easy way to edit your ACLs. Sure, you can use the command line, but holy mackeral, it's complicated & non-intuitive. Don't believe me? Read this (& here's a simpler, kinder one, & it's still a bit complicated ...

"Enhancments to the Fast Filesystem to support Multi-Terabyte Storage Systems" 4:34 PM Long way to say 64-bit block pointers * making a substantial change to to system gives you a chance to change other things, too. 4:36 History * Traditional FFS used 32-bit block pointers * Limited to about 4 terabytes * Inodes running out of room to add new functionality. * Linear searches of large directories are time-consuming 4:38 Development * UFS and UFS2 code base combined for development because they share so much code * indoes increased from 128 to 256 bytes * Retain directory format ** 32-bit inode numbers ** existing linear scan but with hooks for in index to possibly be added later ** POSIX defiens a 32-bit inode number ** Probably change to 64-bit at some point * Retain idea of cylinder groups but eliminate all geometry information ** We no longer know enough about geometry to use it effectively. ...