Examples for udev-created tape device nodes

7.1 LPAR mode z/VM guest

If you use udev-created device nodes, be sure that you use the nodes according to your distribution.

Note: The format of the nodes that udev creates for you depends on distribution-specific configuration files in /etc/udev/rules.d. The following examples use hypothetical nodes that are provided for illustration purposes only.

If your distribution provides udev, you can use udev to create tape device nodes for you. udev is a utility program that can use the device information in sysfs to create device nodes.

Typically, udev creates device nodes that are based on the device names. Other udev-created device nodes can be based on device bus-IDs. The device name and, therefore, the standard device node of a device can change when Linux® is rebooted. In contrast, the mapping of devices and device nodes that are based on bus-IDs is persistent across reboots. This mapping changes only if you change the bus-IDs of your devices. With these device nodes, udev helps you to reliably address a particular device.

The configuration file might instruct udev to create the following two nodes for each logical device:
  • The standard node
  • A node that is based on the device bus-ID
For a tape device with a device bus-ID 0.0.01ac, it would create four device nodes.
Nodes for the non-rewinding character device
  • /dev/ntibm0 (standard device node according to the tape naming scheme)
  • /dev/tape/0.0.01ac/non-rewinding
Nodes for the rewinding character device
  • /dev/rtibm0 (standard device node according to the tape naming scheme)
  • /dev/tape/0.0.01ac/rewinding