Wiki source code of Xen

Last modified by Sebastian Marsching on 2022/03/27 15:37
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3 {{warning}}
4 This page was migrated from an old version of this Wiki where it was last updated on 2010-05-17. This means that the information on this page might be outdated.
5 {{/warning}}
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7 # Clock issues
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9 Usually Xen will try to sync the clocks of Dom0 and the DOMUs, however this might not work as expected. In order to make a DomU maintain the clock on its own, one has to set `/proc/sys/xen/independent_wallclock` to `1`.
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11 # Upgrading Xen server from Ubuntu 7.10 to 8.04
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13 See [http://sebastian.marsching.com/blog/archives/89-Making-Xen-work-on-Ubuntu-8.04-Hardy-Heron.html](http://sebastian.marsching.com/blog/archives/89-Making-Xen-work-on-Ubuntu-8.04-Hardy-Heron.html)
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15 # Upgrading Xen DomU from Ubuntu 8.04 (hardy) to 10.04 (lucid)
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17 * Ubuntu 10.04 does not run with kernel 2.6.24, so install `linux-server` in Xen DomU and copy `vmlinuz-*` and `initrd-*` to Xen Dom0, so that the DomU can be booted with the new kernel.
18 * Disk devices are now available as `/dev/xvdaX` instead of `/dev/sdaX`, so change `root` line in DomU configuration and entries in `/etc/fstab` of DomU.
19 * In DomU configuration, change `extra` line from `xencons=tty` to `console=hvc0`. You also have to copy `/etc/init/tty1.conf` to `/etc/init/hvc0.conf` within the DomU and replace all occurrences of `tty1` in the copied file with `hvc0`.
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21 # Using a special IP setup with Xen
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23 See [http://wiki.hetzner.de/index.php/9_IP_Adressen_mit_Ubuntu](http://wiki.hetzner.de/index.php/9_IP_Adressen_mit_Ubuntu) (German only)
24
25 # Bad network perfomance in Xen DomU
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27 If you are using a routed networking setup with Xen, you might encounter a bad network performance for the Xen DomU: The solution is to disable tx checksums for the virtual ethernet device: They are not needed as their are no physical errors on a virtual interface that only connects to another virtual interface in the Dom0. To disable tx checksums the following line can be added to `/etc/network/interfaces`
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29 post-up ethtool -K eth0 tx off
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31 This line has to be added within the definition of the corresponding interface and `eth0` has to be replaced by the name of this interface.
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33 Please note that this solution will not work with Ubuntu, if `/usr` is in the DomU is stored on its own partition: You will have to deactivate the `ifup` and `ifdown` hooks in `/etc/udev/rules.d/85-ifupdown.rules` because `ethtool` lies in `/usr/sbin` and `/usr` is not yet mounted when this hooks are executed. Deactivating this hooks probably won't hurt as the interfaces will be brought up by `/etc/init.d/networking` and you are unlikely to use a hotplugged interface within a Xen DomU. In newer Ubuntu releases (e.g. 10.04 - lucid lynx) this is not so easy, as the the network interfaces are managed by upstart. Therefore you have to copy `ethtool` to the root partion and use the corresponding path in the `post-up` script.