Mastering POSIX File Capabilities

An anonymous reader passes along an IBM DeveloperWorks article on POSIX file capabilities, which have recently become available in the Linux kernel; they are expected in the mainline kernel by 2.6.24. POSIX file capabilities parcel out root user powers into smaller privileges. The article details how to program using file capabilities and how to switch on the ability of a system's setuid root binaries to use file capabilities.

Comments

OT: ACLs

[Richard W.M. Jones]

Well, the article is about capabilities, not ACLs, and Linux has had ACLs in the filesystem for years too.

To get to the point though: Administrators don't use ACLs on Linux because they make file permissions much harder to understand, for what is in reality an unimportant increase in expressiveness. Simple user/other permissions are easy to understand and work 99% of the time, groups fill in another few cases (eg. permissions on shared sockets), and ACLs are almost never necessary.

SELinux is another "interesting" area. Since I started to use Fedora again, I really wanted to use SELinux. I really did. But because I'm always using Rawhide (the bleeding-edge development version) I've had to turn SELinux off. It's too complex to understand and breaks too often on Rawhide. I'd only recommend it on a stable version (eg. RHEL/Centos) and then just as a final line of defense security measure, not to implement ACLs.

Rich