The following description of the behavior of USB devices when sessions are connected and disconnected from a client applies only to USB serial devices. Other device classes may have different semantics regarding ownership and device lease times.

Changing the active session on a client changes the ownership of the device nodes to the user associated with the new session. A session change occurs whenever a user inserts or removes a smart card from a client or logs into a session.

In a failover environment, you can use the utselect or utswitch command to change a session. A session change causes all devices currently open by a non-root user to be closed after 15 seconds. Any input to or output from any affected device results in an error. For a serial device node, if the original session is restored within 15 seconds, the ownership is not relinquished, and input and output continue uninterrupted.

Devices currently opened by the superuser, including normal printing, remain unaffected by a session change.