facl in laments terms

[Guest_imported]

Hello all,
I've read over the man page on facl and it's just a bit confusing to me. Could anyone lay it out for me in laments terms?
My first impression of what an acl is, is that it's a "sub-mask" for file permissions? Thanks.

 

[mkharris]

The problem with 'vanilla' file access permissions are that they are not very flexible. You only have 3 levels to work on - how your own user can access your file, how other users that are in your file's group can access it, and how any other user can access it.

You might want user fred to be able to write to one of your files in a directory, but not the others. There may be some reason that you need all the files in that directory to have the same group ownership. So you have a dilemna. This is where Access Control Lists come in. They allow you to extend the permissions on files, so that you can build a list of users who have different access rights to your file.

That should explain it at the grass blade tip level .