Les and Michael, There are a few ways to workaround the NIC detection issue. Each has its own advantages and limits. The first method is: suppose you or your team have full control of running kernel on your hundreds/thousands of boxes, your can then build some NIC drivers statically in the kernel -- these statically built NIC drivers will be detected as eth0 without glitches -- then leave other different NIC types on the same box still in dynamic kernel modules status. It works greatly if you know all the types of primary network NIC. Typically e100, tg3, etc. and you have already standardized the 2nd NIC on the boxes to one or two brands like e1000. The second method is: suppose you or your team can not control rebuilding of kernel, or at least you have no full control, but you really know the types of primary/secondary NICs combinations on all the Linux boxes in your kingdom. Then you can try the following hack: You can try to add/change lines in /lib/modules/`uname -r`/modules.dep file according to your NICs combinations -- always load the drivers according to your predefined order. For example: .../e1000.ko: .../tg3.ko .../3c59x.ko .../e100.ko .../forcedeth.ko .../forcedeth.ko: .../tg3.ko The above means to load the module at left, system will first load modules at right! So tg3|3c59x|e100|forcedeth always load before e1000, and tg3 load before forcedeth. The same idea can be applied to all NIC combination types your have and can be set only once and applied to all your linux boxes if you set it up correctly. The side-effect is: you have waste few hundreds Kilobytes memory, but who cares? There are also other tricks I tried before, some works and some not. But I think the above should probably work for most general cases. Have a good weekend. --Guolin -----Original Message----- From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On Behalf Of Michael D. Kralka Sent: Thursday, January 10, 2008 6:52 AM To: CentOS mailing list Subject: Re: [CentOS] Nic order detection Les Mikesell wrote: > I do have the ifcfg-ethX files for the 2 interfaces that are currently > active, but since the machines were built by image copies of a master > disk, they do not have HWADDR address entries. A person on-site with > access to the console adjusted them if they didn't come up right the > first time, but they seem to shift around on each reboot. Will adding > the HWADDR entry nail them down even if it doesn't match the nic type > specified in modprobe.conf? Can someone point me to the code where this > happens? Until recently the machines were running centos 3.x and this > seems to be a difference in behavior. As already pointed out, yes adding HWADDR will "nail them down" and the entries in modprobe.conf don't mean much. If you (or a script) execute "modprobe eth0" it will load the appropriate module. Unfortunately, this is not how CentOS 5 loads drivers. With CentOS 5, udev is used to load the drivers by looking at the "modalias" file found for each device under the /sys directory (search for them, there are many). For PCI devices, the modalias includes the 4 16-bit PCI ID values, the PCI device type, and some other information. Unfortunately, udev tries to be clever and loads drivers in parallel. As a result, if there are NICs that use different drivers, the order that the NICs are assigned ethX interfaces is left to the whim of the Linux scheduler (i.e. is non-deterministic). Devices using the same driver will always be assigned interface names in the same relative ordering. If they all use the same driver, they will always be assigned the same names, without having to fuss with the HWADDR option (this is due to how drivers enumerate PCI devices). In reality, HWADDR doesn't force the kernel to assign the desired interface to each device. It simply "cleans up" after udev by renaming the interfaces from what the kernel assigned to each NIC to the interfaces you expect. Search for "rename_device" in ifup-eth and network-functions, both found in the /etc/sysconfig/network-scripts directory. Cheers, Michael _______________________________________________ CentOS mailing list CentOS at centos.org http://lists.centos.org/mailman/listinfo/centos