qeth interface names and device directories

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7.1 LPAR mode z/VM guest

The qeth device driver automatically assigns interface names to the qeth group devices and creates the corresponding sysfs structures.

According to the type of CHPID and feature used, the Linux® naming scheme uses the following base names:
eth<n>
for Ethernet features (including the OSA-Express ATM device when it emulates Ethernet).
hsi<n>
for HiperSockets™ devices.
where <n> is an integer that uniquely identifies the device. When the first device for a base name is set online it is assigned 0, the second is assigned 1, the third 2, and so on. Each base name is counted separately.

For example, the interface name of the first Ethernet feature that is set online is eth0, the second eth1. When the first HiperSockets device is set online, it is assigned the interface name hsi0.

While an interface is online, it is represented in sysfs as: 
/sys/class/net/<interface>

In Linux distributions, a user-space component typically assigns a predictable name to the network interface, for example enc+device number for OSA and HiperSockets. Often these components rename the interfaces quickly, and you might see multiple instances of [interface_name]: renamed from eth0 in the log file.

The qeth device driver shares the naming scheme for Ethernet interfaces with other network device drivers. Each driver uses the name with the lowest free identifier <n>, regardless of which device driver occupies the other names. For example, assume that the first qeth Ethernet feature is set online and there already is a PCI network function online. Then the PCI function is named eth0 and the qeth feature is named eth1.

The mapping between interface names and the device bus-ID that represents the qeth group device in sysfs is preserved when a device is set offline and back online. However, it can change when rebooting, when devices are ungrouped, or when devices appear or disappear with a machine check.