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Thread: Setting sysctl variables

  1. #1
    Join Date
    Feb 2007

    Default Setting sysctl variables

    I'm trying to tighten up TCP/IP stack settings on my Link-4 Ubuntu 6.06 machine, and I was surprised to find this:

    # echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
    bash: /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts: Operation not permitted
    # sysctl -w net.ipv4.tcp_syncookies=1
    error: "Operation not permitted" setting key "net.ipv4.tcp_syncookies"
    So neither the sysctl utility nor the plain echo method of setting sysctl variables work. (Running as root, obviously.) I'm puzzled. Is this an OpenVZ limitation?

  2. #2


    I believe that's just the same as attempting to modify kernel settings, which we aren't capable of doing. So yah, it would be a limitation of the OpenVZ software I'm afraid.

  3. #3
    Join Date
    Jun 2008

    Default Cant set sysctl - high latency

    In a desperate attempt to improve the network performance between my east coast (DC) computer and my CentOS 5 VPS, I found that I am also unable to use sysctl to set
    to larger values. Why is that?

    My goal is to overcome my 130ms latency (yuck!), and get at least a few times better than my current 30-60kB/s (also measured on vpslink's My computer's connection is capable of 1.9MB/s on a large file from another web hosting account @90ms latency. I figure I should at least be able to get several times the current slow throughput from this VPS. I am obviously about to change DNS back over to my old shared hosting provider and give up on VPSLink.

    I was attempting to raise the TCP window size for the server, since latency seems to be not particularly good even from west coast connections I have tried.

    Anyone have any suggestions?
    Thanks, Scott

    (from DC)

    5 18 ms 8 ms 7 ms []
    6 86 ms 89 ms 89 ms []
    7 98 ms 106 ms 106 ms []
    8 133 ms 142 ms 143 ms []
    9 141 ms 142 ms 142 ms []
    10 138 ms 133 ms 135 ms []
    11 134 ms 138 ms 139 ms

  4. #4
    Join Date
    Jun 2008


    *ignore* Are you on Xen or Virtuozzo?

    Nevermind. Yes, it is a limitation on VZ. If you want more control, consider a Xen VPS.
    Last edited by The Universes; 06-26-2008 at 05:49 PM.
    Note: my views are my own and do not reflect those of VPSLink


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