[systemd-devel] 70-persistent-net.rules

[Colin Guthrie]

'Twas brillig, and Reindl Harald at 11/04/13 11:55 did gyre and gimble:
> 
> 
> Am 11.04.2013 12:41, schrieb Colin Guthrie:
>> 'Twas brillig, and Andrey Borzenkov at 11/04/13 10:25 did gyre and gimble:
>>> On Thu, Apr 11, 2013 at 2:50 AM, Reindl Harald <h.reindl at thelounge.net> wrote:
>>>> /usr/share/doc/systemd/README.Fedora-18
>>>>
>>>> - A hacky workaround that allows udev to rename network interfaces into
>>>>   kernel's ethX namespace has been re-added. This is to support users who still
>>>>   rely on udev rules such as 70-persistent-net.rules generated in previous
>>>>   Fedora releases to name their network interfaces. Note that the workaround is
>>>>   only temporary and will go away in a future Fedora release
>>>> ______________________________________
>>>>
>>>> PLEASE DO NOT remove this mechanism
>>>>
>>>> well, you are not creating it since a long time, BUT do not
>>>> stop use this config file if it is present!
>>>>
>>>
>>> Mmm ... if rules file exists in correct directory it of course will be
>>> used. Or do you mean to not remove auto-generation of this file?
>>
>> Isn't the mechanism used to shuffle around conflictingly named
>> interfaces gone from udev these days (it is after all racy and buggy).
>>
>> If so then things might not work nicely when processing the old rules.
>> Users should be strongly encouraged to migrate to the persistent network
>> interface names which avoids the design flaws inherent with the
>> previously approach.
> 
> that is all nice in theory
> in real life there are THOUSANDS of setups with only one ethernet interface
> there are THOUSANDS of virtual machines with only one network interface
> there are THOUSANDS of virtual machines with only two NICs and no race-problems
> 
> there are MANY THOUSANDS of configs and scripts for routing, firewalls and
> automation on all this machines and only god knows what amount of work and
> side effects it brings to change this all for zero benefit
> 
> this are facts from the real life and as much i agree with the race problems
> i really do not want to change interface names on remote-machines which
> are not in a datacenter and have no LOM hundrets of kilometers way and so
> i need a long-term way to have my eth0 and in very few cases eth1 too


I accept that rationale and see your point, but the fact that the code
is a bad concept is something that should still be strongly discourage.

Any scripts that assume names are also broken by design and should
really be written better to deal with things more gracefully, although I
totally agree that breaking existing setups is bad.

But on the other hand I haver personally been locked out of my machine
at a data centre and had to endure several hours of downtime as a result
of the network interfaces randomly "flipping" after a reboot, so I do
really also want to see the correct design filter through and become
best practice and the accepted standard.

But regardless, unless the patch to allow renaming is carried locally in
the distro for a long time
(http://pkgs.fedoraproject.org/cgit/systemd.git/tree/0005-F18-Revert-udev-network-device-renaming-immediately-.patch?h=f18)
then eventually the support will have to disappear - but ultimately this
is something to discuss with your distro.

That said, it is interesting that Fedora, Suse and ourselves at Mageia,
all carry this patch in our releases (although it's gone from F19
looking at the git).

Col



-- 

Colin Guthrie
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