Amazon EC2 and “4gb seg fixup”

Tonight I spent two hours banging on an EC2 instance that suddenly went awry. I was adding SSL to a couple of internal applications we host on this instance when my “apache2ctl configtest” command hung. I tried all sorts of things and finally noticed there were tons of entries in /var/log/messages referencing “4gb seg fixup” like this:

kernel: printk: 16 messages suppressed.
kernel: 4gb seg fixup, process sh (pid 21236), cs:ip 73:00a7b240
last message repeated 8 times
kernel: printk: 353387 messages suppressed.

Google revealed that I’m not the first to run into this problem with an EC2 instance. Several posts said to install the Xen version of libc

apt-get install libc6-xen 

and do this:

echo "hwcap 0 nosegneg" > /etc/; ldconfig

And then reboot.

This seems to have fixed it, but I’m wondering why this was either not included in the Ubuntu AMI I’m using or somehow got undone.

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4 Responses to Amazon EC2 and “4gb seg fixup”

  1. Pingback: Eric Mason . net » Blog Archive » Multiple virtual hosts using SSL on the same IP and Port

  2. Eric Hammond says:

    Thanks for tracking this down. If you can send me the reference, I’ll take a look at it for the next Ubuntu AMI release on

  3. You’re a frikkin GENIUS. I was about to blow away the whole image and give up – had found references to needing an install of libc6-xen, but where did you find the other piece?

  4. Jes5199 says:

    worked for me! I’m using the Alestic debian AMIs, and one of them mysteriously never caught this problem. I don’t know what makes it start, but this incantation certainly makes it stop.

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