HVC terminal devices

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The z/VM® IUCV HVC device driver is a kernel module that uses device nodes to enable HVC terminal devices to communicate with getty and login programs.

There can be up to 8 HVC terminal devices, hvc0 to hvc7. hvc0 can be activated to receive Linux™ kernel messages. The terminal IDs for HVC terminal devices match the device names with a leading lnx. For example, the terminal ID for hvc0 is lnxhvc0.

Figure 1. Login through HVC terminal devices

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Connection requests are created with the iucvconn program on the terminal server. A request includes the z/VM user ID of the target z/VM guest virtual machine and the terminal ID of an HVC terminal device.

The z/VM IUCV HVC device driver maps the terminal ID to the corresponding terminal device. As of kernel 3.14, lnxhvc can be used as a generic terminal ID that maps to any free HVC terminal device.

A systemd instance unit, an inittab entry, or an Upstart job file associates the HVC terminal device with a login program.