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THpubs
Asked: 2012-06-05 19:53:44 +0800 CST

Why does upgrading to 12.04 on an OpenVZ VPS warn that the kernel size is 0?

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When I tried to upgrade my server to ubuntu 12.04, it gave this message, but the upgrade process will continue :

 WARNING:root:estimate_kernel_size_in_boot() returned '0'?

This is a VPS server on openvz. I just upgraded from 11.04 to 11.10 without any problems. But what to do now?

server

1 Answers

  1. Best Answer

    But what to do now?

    Continue. The warning is expected, since OpenVZ VPSs do not have their own kernels -- they operate on the physical host's kernel. OpenVZ is more like an enhanced chroot rather than a true virtual machine in that respect.

    Important - if your running kernel is less than 2.6.24

    Please check your current kernel version with uname -r. If it is less than 2.6.24, the upgrade will fail half-way with a glibc error. That happens because the glibc included by default with 12.04 requires a minimum 2.6.24 kernel -- glibc are the critical C libraries used by every application.

    At that point, you will need the instructions [from this answer], as pasted below:

    I've set up a PPA containing a recompiled libc which is compiled to work on 2.6.18 or newer (please check uname -r!), and it should override the current libc provided by Precise. Just add ppa:izx/ovz-libc, update, and it should let you get past this. Specifically, something like this:

    apt-add-repository ppa:izx/ovz-libc
apt-get update
apt-get -f install
do-release-upgrade

    and continue on until the upgrade completes successfully. I highly recommend NOT replacing any changed or non-existent config files.

    I will be keeping the ppa updated as and when libc is updated upstream. The PPA package includes a pin so that it will only be updated when the new fixed libc is available on the PPA, not when it first appears in the official repositories.

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