% Registration Glen or Glenda: Empowering Users and % Applications with Private Namespaces % Eric Van Hensbergen (bergevan@us.ibm.com) Private namespaces were first introduced into Linux during the 2.4 kernel series. Their use has been limited due to namespace manipulation being considered a privileged operation. Giving users and applications the ability to create private namespaces as well as the ability to mount and bind resources is the key to unlocking the full potential of this technology. There are serious performance, security and stability issues involved with user-controlled dynamic private namespaces in Linux. This paper will propose a mechanism for maintaining system integrity while unlocking the power of dynamic namespaces for normal users. It will go on to discuss relevant potential applications of this technology including its use with FUSE (Filesystem in Userspace), v9fs (the Linux port of the Plan 9 resource sharing protocol) and Plan 9 from User Space (the Plan 9 application suite including userspace synthetic file servers ported to UNIX variants).