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Biosdevname and renaming of Ethernet interfaces
 Road to hell in paved with good intentions


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Loss of architectural integrity of Unix is now very pronounced in RHEL. Both RHEL6 and  RHEL7 although 7 is definitely worse. And this is not only systemd fiasco. For example, recently I spend a day troubleshooting an interesting and unusual problem: one out of 16 identical (both hardware and software wise) blades in a small HPC cluster (and only one) failed to enable bonded interface on boot and this remained off line. Most sysadmins would think that something is wrong with hardware. For example, Ethernet card on the blade and/or switch port or even internal enclosure interconnect. I also initially thought his way. But this was not the case  ;-)  

Tech support from Dell was not able to locate any hardware problem although they did diligently upgraded CMC on enclosure and BIOS and firmware on the blade. BTW this blade has had similar problems in the past and Dell tech support once even replaced Ethernet card in it, thinking that it is culprit. Now i know that this was a completely wrong decision on their part, and waist of both time and money  :-), They come to this conclusion by swapping the blade to a different slot and seeing that the problem migrated into new slot. Bingo -- the card is the root cause.  The problem is that it was not.  What is especially funny is that replacing the card did solve the problem for a while. After reading the information provided below you will be as puzzled as me why it happened. 

But after yet another power outage the problem  returned.

This  time I started to suspect that the card has nothing to do with the problem. After more close examination I discovered that in its infinite wisdom in RHEL 6 Red Hat introduced a package called biosdevname. The package was developed by Dell (the fact which seriously undermined my trust in Dell hardware ;-).

This package renames interfaces to a new set of names, supposedly consistent with their etching on the case of rack servers. It is useless (or more correctly harmful) for blades.  The package is primitive and does not understand that server is a rack server or blade.

Moreover by doing this supposedly useful remaining this package introduces in  70-persistent-net.rules file a stealth rule:

KERNEL=="eth*", ACTION=="add", PROGRAM="/sbin/biosdevname -i %k", NAME="%c"

I did not look at the code but from the observed behaviour it looks that in some cases in RHEL 6 (and most probably in RHEL 7 too) the package adds a "stealth" rule to the END (not the beginning but the end !!!) of  /udev/rules.d/70-persistent-net.rules file, which means that if similar rule in 70-persistent-net.rules exits it is overwritten. Or something similar to this effect. 

If you look at Dell knowledge base there are dozens of advisories related to this package (search just for biosdevname). Which suggests that there some deeply wrong with its architecture.

What I observed  that on some (the key word is some, converting the situation in Alice in Wonderland environment) rules for interfaces listed in  70-persistent-net.rules file simply does not work if this package is enabled. For example Dell Professional services in their infinite wisdom renamed interfaces  back to eth0-eth4 for Inter X710 4-port 10Gb Ethernet card that  we have on some blades. On 15 out of 16 blades in the Dell enclosure this absolutely wrong  idea works perfectly well. But on blades 16 sometimes it does not as a result this blade does not boot after power outage of reboot. When this happens is unpredictable. Sometimes it  boots, but sometimes it does not.  And you can't understand what is happening, no matter how hard you try because of stealth nature of changes introduced by biosdevname package. 

Two interfaces on this blades (as you now suspect eth0 and eth1) were bonded on this blade. After around 6 hours of poking around the problem I discover that despite presence of rule for "eth0-eth4 in 70-persistent-net.rules file RHEL 6.7 still renames on boot all four interfaces to em0-em4 scheme and naturally bonding fails as eth0 and eth1 interfaces do not exit.

First I decided to deinstall biosdevname package and see what will happen. Did not work (see below why -- de-installation script in this RPM is incorrect and contains a bug -- it is not enough to remove files  you also need to run  the command update-initramfs -u (Hat tip to Oler).

Searching for "Renaming em to eth" I found a post in which the author recommended disabling this "feature" via adding biosdevname=0 to kernel parameters /etc/grub.conf

That worked.  So two days my life were lost for finding a way to disable this completely unnecessary for blades RHEL "enhancement".

Here is some information about this package

Copyright (c) 2006, 2007 Dell, Inc.  
Licensed under the GNU General Public License, Version 2.

biosdevname in its simplest form takes a kernel device name as an argument, and returns the BIOS-given name it "should" be.  This is
necessary on systems where the BIOS name for a given device (e.g. the label on the chassis is "Gb1") doesn't map directly 
and obviously to the kernel name (e.g. eth0).
The distro-patches/sles10/ directory contains a patch needed to integrate biosdevname into the SLES10 udev ethernet 
naming rules.This also works as a straight udev rule.  On RHEL4, that looks like:
KERNEL=="eth*", ACTION=="add", PROGRAM="/sbin/biosdevname -i %k", NAME="%c"
This makes use of various BIOS-provided tables:
PCI Confuration Space
PCI IRQ Routing Table ($PIR)
PCMCIA Card Information Structure
SMBIOS 2.6 Type 9, Type 41, and HP OEM-specific types
therefore it's likely that this will only work well on architectures that provide such information in their BIOS.

To add insult to injury this behaviour was demonstrated on only one of 16 absolutely identically configured Dell M630 blades with identical hardware and absolutely identical (cloned) OS instances.  Which makes RHEL kind of "Alice in Wonderland" system. After this experience it is difficult not to hate Red Hat, but we can do very little to change this situation to the better. 

This is just one example. I have more similar  stories to tell

I would like to stress that  the fact that the utility that is included in this package does not understand that it the target for installation is a blade ( there is no etching on blade network interfaces ;-) or server is a pretty typical RHEL behaviour, despite the fact that the package was developed by Dell. They also install audio packages on boxes that have no audio card and do a lot of similar things ;-) 

If you look at this topic using your favorite search engine (which should be Google anymore ;-) you will find dozens of posts in which people try to resolve this problem with various levels of competency and success. Such a tremendous waist of time and efforts.  Among best that I have found were:

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