udhcpc: sending discover



  • Hello folks

    I have few sites I can’t get ip quick enough before fog gives up. Boot to PXE fine. No issues, gets IP address. Fog runs down some scripts and when it normally starts sending the image part it trys to get IP again from DHCP. During that part of this, does it give sending discover. I watch the switch and it turns green right when it assay failed to get IP via DHCP! Tried on interfaces enp1s0
    Please check your network setup and try again!

    I don’t see any choice within fog to address this problem. Suggestions?


  • Moderator

    @jhalbert Understand I’m NOT recommending you turn off spanning tree, only change its mode to one of the fast spanning tree protocols. The fast protocols use optimistic blocking (forward first then listen for BPDU) instead of pessimistic (block while listening for BPDU) that standard stp uses.

    Is there a way to do it without changing the network, yes but it will require a little work on your part (honestly you need to enable RSTP to fix it for all). You will need to unpack the init.xz file. Its located on the fog server in /var/www/html/fog/service/ipxe directory. The instructions for unpacking and packing the inits are here: https://wiki.fogproject.org/wiki/index.php/Modifying_the_Init_Image Follow the 1.0.0 and up instructions. Once they are unpacked in the unpacked directory you need to edit a file in ./etc/init.d called S40Network. Just before the udhcpc command add in a line that says sleep 27 Save the file and then repack the inits and move to the /var/www/html/fog/service/ipxe directory.

    What that will do is have FOS Linux pause for 27 seconds on every boot to let the network settle before trying to dhcp boot.



  • @george1421 That is what I was reading. I know its spanning tree because I am imaging computers with my netgear switch that is $30. I was wondering if there is any work around. Maybe make Linux wait longer? Even 10 more secs would solve my problem. I am on site because I could not reimagined this pc remotely. I know its my whole site but I can’t turn that feature off. It has already save me few times.


  • Moderator

    When this typically happens, its not a fog issue but an infrastructure one. This is symptomatic of having spanning tree enabled on the business switch but not having one of the fast STP protocols enabled (RSTP, MSTP, fast-STP, portfast, or what ever your switch mfg calls it).

    A quick test to see if its a spanning tree issue is to put an unmanged (read cheap dumb switch) in between the pxe booting computer and the building network switch.

    The issue is FOS Linux boots so fast, it gives up before traditional spanning tree starts forwarding data on the switch port. For traditional STP, it waits for 27 seconds listening for a BPDU packet. If it doesn’t hear one then it starts forwarding data on the port.


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