Hello,
I've read about consistent network device naming here :
-
https://www.freedesktop.org/software/systemd/man/systemd.net-naming-scheme.html
- https://www.freedesktop.org/software/systemd/man/systemd.link.html#
and here
-
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/configuring_and_managing_networking/index#consistent-network-interface-device-naming_configuring-and-managing-networking
But I still cannot explain neither how exactly it works on CentOS nor a
change I experienced in the onboard ethernet device's name when updating
my system (runing systemd-udev-239) from CentOS 8.1 to CentOS 8.2 (i386)
with one method but not with another one :
Starting from CentOS 8.1 where the onboard ethernet device name was
eno1np0, I tried :
a) to reinstall with a kickstart based mechanism (via the xCAT HPC
provisioning software) pointing to the 8.2 repos
-> device name stayed the same once booted in CentOS 8.2
# udevadm info /sys/class/net/eno1np0 | grep ID_NET
E: ID_NET_DRIVER=bnxt_en
E: ID_NET_LINK_FILE=/usr/lib/systemd/network/99-default.link
E: ID_NET_NAME=eno1np0
E: ID_NET_NAME_MAC=enx3cecef4247de
E: ID_NET_NAME_ONBOARD=eno1np0
E: ID_NET_NAME_PATH=enp198s0f0np0
This is what I was expecting.
b) to update to 8.2 running yum update
-> device name changed to enp198s0f0np0
- I did not change any udev rules
- I did not change NamePolicy (NamePolicy=kernel database onboard slot path)
- I did not disable anything relative to consistent naming with neither
net.ifnames=0 nor biosdevname=0
According to this policies order, it seems legit to me to end up with
onboard naming scheme. But how could I have in the yum update case ended
up with a path naming scheme ?
In a more general way, I don't fully understand how the rename is
supposed to be done and/or the link between NamePolicy and udev renaming
rules as they don't seem to apply to ID_NET_NAME_* names
For instance, on CentOS, you go through the following rules :
- 60-net.rules calling /lib/udev/rename_device
which I don't think match my case as my config files has no HWADDR var set :
# Generated by parse-kickstart
TYPE="Ethernet"
DEVICE="eno1np0"
UUID="8482a953-65dc-4814-b6b4-a9d9c7edc4a1"
ONBOOT="yes"
BOOTPROTO="dhcp"
IPV6INIT="yes"
So I should go to
- 71-biosdevname.rules calling biosdevname
SUBSYSTEMS=="pci", PROGRAM="/sbin/biosdevname --smbios 2.6 --nopirq
--policy physical -i %k", NAME="%c" OPTIONS+="string_escape=replace"
which should in my case set the NAME var to em1 as this is the output of
the command when run manually
- 75-net-description.rules which calls IMPORT{builtin}="net_id"
-> is this what sets the ID_NET_NAME_* udev properties ?
Does this step somehow use the NAME var set after biosdevname ?
- 80-net-setup-link.rules
IMPORT{builtin}="net_setup_link"
NAME=="", ENV{ID_NET_NAME}!="", NAME="$env{ID_NET_NAME}"
What I understand here in my case is that NAME is not empty (because of
biosdevname step) so I don't understand why I don't end up with em1
instead of the
onboard style name. This would mean ID_NET_NAME has been set in a
previous step ? What was the use of the biosdevname stop then ?
finally, what does "If the kernel claims that the name it has set for a
device is predictable" mean
(https://www.freedesktop.org/software/systemd/man/systemd.link.html#) ?
And what is the kernel name (%k) : is it always ethX ?
Thanks for your help
--
Thomas HUMMEL
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