Editing 028 to 042 kernel upgrade

This article describes a way to upgrade your old OpenVZ system with RHEL5-based
(028stabNNN kernel) to RHEL6-based (042stabNNN) kernel, and convert /vz
from ext3 to ext4, while keeping RHEL/CentOS 5 as a host OS.

Assumptions:
* systems is CentOS (RHEL) 5.x
* vzkernel is 028stabXXX, i.e. RHEL5-based
* /vz uses ext3

End result should be:
* Same CentOS 5 system
* vzkernel is 042stabXXX
* /vz uses ext4

== Update your system ==

 yum update

Install required software:

 yum install e4fsprogs.x86_64

== Add rhel6 kernel repos ==

Disable rhel5 and enable rhel6 OpenVZ kernel repository.
In other words, change <code>/etc/yum.repos.d/openvz.repo</code>
to look like this (changes required are '''in bold'''):

   [openvz-kernel-rhel6]
   name=OpenVZ RHEL6-based stable kernels
   <nowiki>#baseurl=http://download.openvz.org/kernel/branches/rhel6-2.6.32/current/</nowiki>
   <nowiki>mirrorlist=http://download.openvz.org/kernel/mirrors-rhel6-2.6.32</nowiki>
   '''enabled=1'''
   gpgcheck=1
   <nowiki>gpgkey=http://download.openvz.org/RPM-GPG-Key-OpenVZ</nowiki>
   '''#exclude=vzkernel-firmware'''

   [openvz-kernel-rhel5]
   name=OpenVZ RHEL5-based kernel
   <nowiki>#baseurl=http://download.openvz.org/kernel/branches/rhel5-2.6.18/current/</nowiki>
   <nowiki>mirrorlist=http://download.openvz.org/kernel/mirrors-rhel5-2.6.18</nowiki>
   '''enabled=0'''
   gpgcheck=1
   <nowiki>gpgkey=http://download.openvz.org/RPM-GPG-Key-OpenVZ</nowiki>


== Install new OpenVZ kernel ==

 # yum install vzkernel.x86_64

== Check bootloader configuration ==

Make sure 042stab kernel is there and will boot by default:

   cat /boot/grub/grub.conf
 
   timeout 5
   default 0
   title OpenVZ (2.6.32-042stab081.8)
   root (hd0,1)
   kernel /vmlinuz-2.6.32-042stab081.8 ro root=/dev/sda3 vga=0x317 selinux=0 sysfs.deprecated=1
   initrd /initrd-2.6.32-042stab081.8.img
   
   title OpenVZ (2.6.18-348.16.1.el5.028stab108.1)
   root (hd0,1)
   kernel /vmlinuz-2.6.18-348.16.1.el5.028stab108.1 ro root=/dev/sda3 vga=0x317 selinux=0
   initrd /initrd-2.6.18-348.16.1.el5.028stab108.1.img
   ....

== Reboot into new kernel ==

 # reboot

and make sure the system is up and running.

== For linux swraid (mdadm) users with bitmap enabled and low IO write speed, you might need to redo bitmap
cat /proc/mdstat , if chunk size is small  , try (example for internal bitmap) :
mdadm --grow --bitmap=none /dev/md2
mdadm --grow --bitmap=internal --bitmap-chunk=16384 /dev/md2

== Convert /vz to ext4 ==

If your /vz is a separate file system, you need to stop all containers
and umount it first:

 for ve in $(vzlist -1); do vzctl stop $ve; done
 umount /vz

Alternatively, boot the node from a live-CD (such as CentOS 6 live CD).

Check file system:
 # fsck.ext3 -f /dev/sd''xY''

Turn on ext4 features:
 # tune4fs -O extents,uninit_bg,dir_index /dev/sd''xY''

Check the new file system again, as ext4 this time:
 # fsck.ext4 -fpD /dev/sd''xY''

If you have booted from the live CD, you can do the same for root filesystem.

If you have booted from the live CD, do this:
* mount your ROOT and BOOT partitions:
 # mkdir /tmp/root
 # mount /dev/sd''aB'' /tmp/root
 # mount /dev/sd''aC'' /tmp/root/boot
* chroot into it:
 # chroot /tmp/root

Finally, edit <code>/etc/fstab</code>, replacing <code>ext3</code> with <code>ext4</code> for <code>/vz</code> (and <code>/</code> if you converted it as well).
 # vi /etc/fstab

== Create new initrd with proper modules ==

 # KV=042stab083.2
 # mkinitrd -v -f --with=ext4 --without-usb /boot/initrd-2.6.32-${KV}.img 2.6.32-${KV}

Notes:
* you have to add ext4 explicitly
* in RHEL6 kernels USB modules are built-in

== Reboot and enjoy ==

End result is:

      # cat /etc/issue
      CentOS release 5.10 (Final)
      Kernel \r on an \m
      
      # uname -a 
      Linux CentOS-58-64-minimal 2.6.32-042stab081.8 #1 SMP Mon Sep 30 16:52:24 MSK 2013 x86_64 x86_64 x86_64 GNU/Linux

      # df -Th
      Filesystem    Type    Size  Used Avail Use% Mounted on
      /dev/sda3     ext4    259G  1.5G  244G   1% /
       tmpfs        tmpfs     16G     0   16G   0% /dev/shm
      /dev/sda2     ext3    496M   46M  425M  10% /boot
      /dev/sdb1     ext4    1.8T  196M  1.7T   1% /vz

== Next steps ==

You can now install [[ploop]] and enjoy all its benefits.

Also, it makes sense to convert your containers to [[VSwap]].

== See also ==

* [[Quick installation]]

== Acknowledgements ==

This article was originally written by [[User:Denis Hohryakov|Denis Hohryakov]].

[[Category: HOWTO]]