renaming ethernet interface not working

Fri May 6 09:16:36 UTC 2016

On Fri, May 6, 2016 at 10:31 AM, Karl Auer <kauer at biplane.com.au> wrote:
> On Fri, 2016-05-06 at 09:59 +0200, Tom H wrote:
>>
>> 0) "Re-"naming to kernel names isn't recommended, if not actually
>> discouraged.
>
> Can you explain what you mean by "kernel names"? Do you mean "eth0 and
> "wlan0"? If so, how are these special to the kernel?

Yes, eth0 and wlan0 are kernel names. This is what the kernel calls
NICs and this is how udev refers to these names - it then renames them
to "en*" and "wl*" and you'll see "renamed from eth0" and "renamed
from wlan0" in the logs.

> Interestingly, udevadm now shows the new name eth0 as an alias, whereas
> wlan0 is not shown as an alias. Compare (two lines, mailer may fold):
>
> E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/wlan0
> E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/eth0 /sys/subsystem/net/devices/eth0

I'm not sure that this is significant. Perhaps! Or maybe it's just a minor bug.

I have the following on an old laptop when I boot with and without
"net.ifnames=0":

# udevadm info /sys/class/net/eth0
P: /devices/pci0000:00/0000:00:1c.2/0000:13:00.0/net/eth0
E: DEVPATH=/devices/pci0000:00/0000:00:1c.2/0000:13:00.0/net/eth0
E: ID_BUS=pci
E: ID_MM_CANDIDATE=1
E: ID_MODEL_FROM_DATABASE=RTL8111/8168/8411 PCI Express Gigabit
Ethernet Controller
E: ID_MODEL_ID=0x8168
E: ID_NET_DRIVER=r8169
E: ID_NET_LINK_FILE=/lib/systemd/network/99-default.link
E: ID_NET_NAME_MAC=enxf04da29a3351
E: ID_NET_NAME_PATH=enp19s0
E: ID_OUI_FROM_DATABASE=Dell Inc.
E: ID_PATH=pci-0000:13:00.0
E: ID_PATH_TAG=pci-0000_13_00_0
E: ID_PCI_CLASS_FROM_DATABASE=Network controller
E: ID_PCI_SUBCLASS_FROM_DATABASE=Ethernet controller
E: ID_VENDOR_FROM_DATABASE=Realtek Semiconductor Co., Ltd.
E: ID_VENDOR_ID=0x10ec
E: IFINDEX=2
E: INTERFACE=eth0
E: SUBSYSTEM=net
E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/eth0
E: TAGS=:systemd:
E: USEC_INITIALIZED=1369001

# udevadm info /sys/class/net/wlan0
P: /devices/pci0000:00/0000:00:1c.1/0000:12:00.0/net/wlan0
E: DEVPATH=/devices/pci0000:00/0000:00:1c.1/0000:12:00.0/net/wlan0
E: DEVTYPE=wlan
E: ID_BUS=pci
E: ID_MM_CANDIDATE=1
E: ID_MODEL_FROM_DATABASE=BCM4313 802.11bgn Wireless Network Adapter
E: ID_MODEL_ID=0x4727
E: ID_NET_DRIVER=wl0
E: ID_NET_LINK_FILE=/lib/systemd/network/99-default.link
E: ID_NET_NAME_MAC=wlxc0cb380f865a
E: ID_NET_NAME_PATH=wlp18s0
E: ID_OUI_FROM_DATABASE=Hon Hai Precision Ind. Co.,Ltd.
E: ID_PATH=pci-0000:12:00.0
E: ID_PATH_TAG=pci-0000_12_00_0
E: ID_PCI_CLASS_FROM_DATABASE=Network controller
E: ID_PCI_SUBCLASS_FROM_DATABASE=Network controller
E: ID_VENDOR_FROM_DATABASE=Broadcom Corporation
E: ID_VENDOR_ID=0x14e4
E: IFINDEX=3
E: INTERFACE=wlan0
E: SUBSYSTEM=net
E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/wlan0
E: TAGS=:systemd:
E: USEC_INITIALIZED=14150071

# udevadm info /sys/class/net/enp19s0
P: /devices/pci0000:00/0000:00:1c.2/0000:13:00.0/net/enp19s0
E: DEVPATH=/devices/pci0000:00/0000:00:1c.2/0000:13:00.0/net/enp19s0
E: ID_BUS=pci
E: ID_MM_CANDIDATE=1
E: ID_MODEL_FROM_DATABASE=RTL8111/8168/8411 PCI Express Gigabit
Ethernet Controller
E: ID_MODEL_ID=0x8168
E: ID_NET_DRIVER=r8169
E: ID_NET_LINK_FILE=/lib/systemd/network/99-default.link
E: ID_NET_NAME_MAC=enxf04da29a3351
E: ID_NET_NAME_PATH=enp19s0
E: ID_OUI_FROM_DATABASE=Dell Inc.
E: ID_PATH=pci-0000:13:00.0
E: ID_PATH_TAG=pci-0000_13_00_0
E: ID_PCI_CLASS_FROM_DATABASE=Network controller
E: ID_PCI_SUBCLASS_FROM_DATABASE=Ethernet controller
E: ID_VENDOR_FROM_DATABASE=Realtek Semiconductor Co., Ltd.
E: ID_VENDOR_ID=0x10ec
E: IFINDEX=2
E: INTERFACE=enp19s0
E: SUBSYSTEM=net
E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/enp19s0
E: TAGS=:systemd:
E: USEC_INITIALIZED=1364369

# udevadm info /sys/class/net/wlp18s0
P: /devices/pci0000:00/0000:00:1c.1/0000:12:00.0/net/wlp18s0
E: DEVPATH=/devices/pci0000:00/0000:00:1c.1/0000:12:00.0/net/wlp18s0
E: DEVTYPE=wlan
E: ID_BUS=pci
E: ID_MM_CANDIDATE=1
E: ID_MODEL_FROM_DATABASE=BCM4313 802.11bgn Wireless Network Adapter
E: ID_MODEL_ID=0x4727
E: ID_NET_DRIVER=wl0
E: ID_NET_LINK_FILE=/lib/systemd/network/99-default.link
E: ID_NET_NAME=wlp18s0
E: ID_NET_NAME_MAC=wlxc0cb380f865a
E: ID_NET_NAME_PATH=wlp18s0
E: ID_OUI_FROM_DATABASE=Hon Hai Precision Ind. Co.,Ltd.
E: ID_PATH=pci-0000:12:00.0
E: ID_PATH_TAG=pci-0000_12_00_0
E: ID_PCI_CLASS_FROM_DATABASE=Network controller
E: ID_PCI_SUBCLASS_FROM_DATABASE=Network controller
E: ID_VENDOR_FROM_DATABASE=Broadcom Corporation
E: ID_VENDOR_ID=0x14e4
E: IFINDEX=3
E: INTERFACE=wlp18s0
E: SUBSYSTEM=net
E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/wlp18s0
/sys/subsystem/net/devices/wlp18s0
E: TAGS=:systemd:
E: USEC_INITIALIZED=13280281

The value of SYSTEMD_ALIAS for wlp18s0 is repeated, like eth0 in your case.

>> 3) Does copying "/lib/systemd/network/99-default.link" to
>> "/etc/systemd/network/" and changing "NamePolicy=" to
>> "NamePolicy=kernel" keep both kernel names?
>
> I need to know what you mean by "kernel name" before I can answer. But
> would not 10 and 11 mask 99?

"kernel name": see above.

My silly assumption was that you'd move 10 and 11 out of
"/etc/systemd/network/" when testing whether changing the naming
policy works. Sorry.

>> 4) Does setting "net.ifnames=0" at the kernel cmdline keep both
>> kernel names?
>
> Again, need to know what "kernel names" are.

"kernel name": see above.