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Linux VM over Hyper-V : vmbus associated with Network Adapters appear to be random after reboot of Virtual Machine

    Question

  • In a hyper-v based linux virtual machine, vmbus(s) are instantiated.

    They look something like this

    [root@localhost devices]# pwd
    /sys/bus/vmbus/devices
    [root@localhost devices]# ll
    total 0
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_1 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_1
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_10 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_10
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_11 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_11
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_12 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_12
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_13 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_13
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_14 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_14
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_15 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_15
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_16 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_16
    lrwxrwxrwx 1 root root 0 Apr  3 07:02 vmbus_0_17 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_17

    Devices associated with these bus(s) are instantiated when systems starts up

    For example network adapters come up as

    [root@localhost net]# pwd
    /sys/class/net
    [root@localhost net]# ll
    total 0
    lrwxrwxrwx 1 root root    0 Apr  3 09:48 bond0 -> ../../devices/virtual/net/bond0
    -rw-r--r-- 1 root root 4096 Apr  3 09:48 bonding_masters
    lrwxrwxrwx 1 root root    0 Apr  3 09:48 elan1 -> ../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_14/net/elan1
    lrwxrwxrwx 1 root root    0 Apr  3 09:48 elan2 -> ../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_15/net/elan2
    lrwxrwxrwx 1 root root    0 Apr  3 09:48 elan3 -> ../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_16/net/elan3
    lrwxrwxrwx 1 root root    0 Apr  3 09:48 elan4 -> ../../devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A03:00/device:07/VMBus:00/vmbus_0_17/net/elan4

    However, we have seen that vmbus association with corresponding vmbus is not consistent.

    Question:

    Is the bus (number) chosen for individual HW random and does not remain fixed after reboot? If yes, then this is different from standard. Note: We checked this when no changes were done VirtualMachine's setup metadata and no HW was added or removed. We were just rebooting the virtual machine again and again, and we saw the bus association changed after some reboots.


    Monday, April 3, 2017 11:52 AM

All replies

  • Hi Sir,

    This is more related to Linux VM on hyper-v , I'd suggest you post it into following forum:

    https://social.technet.microsoft.com/Forums/windowsserver/en-US/home?forum=linuxintegrationservices&filter=alltypes&sort=lastpostdesc

     

    Best Regards,

    Elton


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    Tuesday, April 4, 2017 8:26 AM
    Moderator