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Thread: 16.04.1 upgraded server does not start network

  1. #1
    Join Date
    Nov 2009
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    60
    Distro
    Ubuntu

    16.04.1 upgraded server does not start network

    Hi, after upgrade from 14.04, my 16.04 virtual machine does not start it's network:

    Code:
    journalctl -b
    shows on eth0

    Code:
    Jul 31 08:01:02 server systemd[1]: Started ifup for eth0.
    Jul 31 08:01:02 server sh[1551]: ifup: interface eth0 already configured
    However, only lo was brought up, ifconfig shows no trace of eth0.

    Code:
    #ifdown eth0
    #ifup eth0
    fixes the situation. For a permanent workaround, I can put these two commands into rc.local

    Any suggestion for what's going wrong here?

    Thanks!

  2. #2
    Join Date
    Mar 2010
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    USA
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    Ubuntu Development Release

    Re: 16.04.1 upgraded server does not start network

    Moved to Virtualization section for better exposure.

    Please post the results of
    Code:
    sudo lshw -class network
    ls /sys/class/net
    ip -o link show | awk '{print $2,$9}'
    cat /proc/net/dev
    I think what we will find, is that the device names have changed. If I look at the bootup messages of "upgraded" Ubuntu virts in my console, I notice a message fly by saying something about eth0 being renamed... but that would be just a legacy convention, that might have fell through for you. Wired strictly being named as eth0 (etc.) is now deprecated.

    Newer systems now use a different naming system for net devices, other than eth0, eth1... ethX; more like Predictable Network Interface Names, with BIOS input and systemd, now show as something like emX or ensX, and are now variably named based on that auto-gen'ed process. Add in that OS'es now can recognise that they are running as virtualized.

    Some people initially fought it, and tried to come up with ways to rename it back to what they were used to... but manually renaming those devices is just more work. If you are just aware that it might have a different name, embrace it, and go with it...
    Last edited by MAFoElffen; August 1st, 2016 at 04:14 PM.
    Concurrent coexistance of Windows, Linux and Unix...
    Ubuntu user # 33563, Linux user # 533637
    Sticky: [all variants] Graphics Resolution- Upgrade /Blank Screen after reboot

  3. #3
    Join Date
    Nov 2009
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    Ubuntu

    Re: 16.04.1 upgraded server does not start network

    Thanks for looking into this. If the devices name has changed, why does a manual ifdown eth0 && ifup eth0 help?

    In any case, these are the outputs immediately after a boot:

    sudo lshw -class network
    Code:
      *-network DISABLED
           description: Ethernet interface
           product: Virtio network device
           vendor: Red Hat, Inc
           physical id: 3
           bus info: pci@0000:00:03.0
           logical name: eth0
           version: 00
           serial: 52:54:00:64:a4:cf
           width: 32 bits
           clock: 33MHz
           capabilities: msix bus_master cap_list rom ethernet physical
           configuration: autonegotiation=off broadcast=yes driver=virtio_net driverversion=1.0.0 latency=0 link=no multicast=yes
           resources: irq:10 ioport:c060(size=32) memory:febf1000-febf1fff memory:febc0000-febdffff
    ls /sys/class/net
    Code:
    eth0
    lo
    ip -o link show | awk '{print $2,$9}'
    Code:
    lo: UNKNOWN
    eth0: DOWN
    cat /proc/net/dev
    Code:
    Inter-|   Receive                                                |  Transmit
     face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
        lo:  166957    2743    0    0    0     0          0         0   166957    2743    0    0    0     0       0          0
      eth0:       0       0    0    0    0     0          0         0        0       0    0    0    0     0       0          0
    Thanks again!

  4. #4
    Join Date
    Nov 2009
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    Ubuntu

    Re: 16.04.1 upgraded server does not start network

    As it turned out, I still had an udev rule 85-ifupdown.rules in /etc/udev/rules.d. Probably a leftover from some old Ubuntu version, this VM exists since 6.06. If I delete this rule, the network comes up reliably.

    Thanks for your help!

  5. #5
    Join Date
    Mar 2010
    Location
    USA
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    Distro
    Ubuntu Development Release

    Re: 16.04.1 upgraded server does not start network

    You are welcome. Yes yours was named eth0, as your update confirmed. That is just something to check now, as it is "not always" that name now. I could see from other output that your link was down... with you seemes to have fixed by changing your udev rules... Those commands help me see what's going on with virtualized network devices. Even on my own. You can't really see a cable plugged in or a link light on a VM Guest.

    Since this is resolved for you now: Please do us a favor and revisit this thread, Link at the upper right of the page "Thread Tools" > Select "Mark Thread as Solved". This help others (later) to search and find answers to their similar problems.
    Last edited by MAFoElffen; August 3rd, 2016 at 06:25 AM.
    Concurrent coexistance of Windows, Linux and Unix...
    Ubuntu user # 33563, Linux user # 533637
    Sticky: [all variants] Graphics Resolution- Upgrade /Blank Screen after reboot

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