Archive for October 16th, 2011

Networking upgrade from Xen 4.0 to 4.1

I believe that Xen 4.1 saw the rewrite of what I’m assuming is the entire network configuration stack. Perhaps the most significant thing for me was that the domU’s network connection isn’t created/initiated properly if the domU config file has anything other than the MAC address and the bridge to which to attach the vif to.

Which meant that my test domU didn’t have a working connection. Oh, it appeared on both systems. Dom0 had a vif1.o show up, and the domU had a eth0 show up. Just that… ifup eth0 would timeout. But removing the ‘network-script=bridge’ component from the domU config file and restarting the domU got the network connection up and running again.

So I have to remember this for when I upgrade the rest of my domUs.

And dom0.

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Scheduling stuff to happen at reboots in Linux

Problem: My 1U is throwing correctable memory errors every few seconds, but I can’t do much about it, so I’m ignoring it.

Solution: Disable the log messages about correctable memory errors.

For future reference, the command is

echo 0 > /sys/module/edac_core/parameters/edac_mc_log_ce

Problem: I don’t want to have to do that after every reboot!

Solution:

  1. Use the module config file (located… somewhere) to disable the messages
  2. Use crontab’s @reboot keyword to run a command at every reboot
Guess which solution I chose.

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The downsides of using old servers as test beds

I managed to forget that Xen needs a PAE enabled kernel on i686. Oops.

On a related note, adding ‘noreboot’ to the Xen command line stops automatic reboots, giving you enough time to read the error message.

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