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  1. #1
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    * OpenVZ Kernel Upgrade: RHEL5 - 6.

    Hello fellow WHT's;

    Got a quick question for fellow administrators. We have a server running on an older redundancy CentOS5 x86 and well its time to move over to RHEL6, just for performance upgrades alone as well as the newer OpenVZ Kernels.

    The Gold Standard in this situation is to obviously re-install the OS to CentOS6 (This along with an upgrade to x64 would probably be advised). However, the issue being a lack of external storage drives at the Datacenter (aka non available) and me being a fair distance away from the rack to carry out a backup or hot swap myself. We do have another server we could switch VM's over from but this seems potentially excessive and will require IP switching and potentially downtime also.

    I have recently noticed a guide that suggests RHEL6 Kernels can be installed on the RHEL5 Kernel. I was wondering if anyone has gone about this; aka has it been achieved safely without loss of data and how stable is it? As, RHEL6 Kernels running on RHEL5 doesn't exactly sound like the best idea to me. Guide: https://openvz.org/028_to_042_kernel_upgrade

    Any advice or personal experience here would be appreciated from anyone who has attempted a similar thing.
    Last edited by ZonedHost; 01-30-2014 at 01:39 PM.
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  2. #2
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    I have heard people of doing this, but I have also heard of plenty messed up and corrupted systems after trying this. However that may just be due to their experience level or something else.

    Have you considered buying or getting a new server from the DC and just doing a 0 downtime migration? OpenVZ makes this very easy and might even allow you to get on some newer hardware?
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  3. #3
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    That guide does work, and it is pretty stable.
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  4. #4
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    Why would you need to re-number? That would be a lot of hassle for your clients, especially if they have to re-number back after you are done upgrading your main server.

    You should get another server in place temporarily on the same subnet as your primary. No sense re-numbering 2 times.

    This will also allow you to take your time with the upgrade and possibly upgrade hardware if needed.
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  5. #5
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    Thanks for the replies guys. So as I suspected, it is a mixed bag. I think I will probably invest in some new hardware and go for a comprehensive server switch and run a live migrate between servers.
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  6. #6
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    Quote Originally Posted by ZonedHost View Post
    Thanks for the replies guys. So as I suspected, it is a mixed bag. I think I will probably invest in some new hardware and go for a comprehensive server switch and run a live migrate between servers.
    That's the safest option.

  7. #7
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    As long as you have a dedicated /vz partition for your VPS data, why not schedule an outage and reinstall the system with CentOS 6? This is a far better solution long-term than bodging it, or going down the unnecessary route of migrating to another server.

    I've done heaps of these and as long as you prepare correctly you can easily remotely reinstall, configure and restore an OpenVZ system in under 1 hour.

  8. #8
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    Quote Originally Posted by PCS-Chris View Post
    As long as you have a dedicated /vz partition for your VPS data, why not schedule an outage and reinstall the system with CentOS 6? This is a far better solution long-term than bodging it, or going down the unnecessary route of migrating to another server.

    I've done heaps of these and as long as you prepare correctly you can easily remotely reinstall, configure and restore an OpenVZ system in under 1 hour.
    That was something I was thinking about (Unmounting the /vz partition in Grub), then reinstalling BOOT image and Kernel etc, then remount the partition. I just need to find a backup source for that partition incase it all goes wrong!
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  9. #9
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    When you run the CentOS installer just choose review/modify existing partition layout, by default it wont touch the existing filesystems. Just format / - obviously beforehand you need to backup /etc/vz/conf and any other configuration files you need.

  10. #10
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    Quote Originally Posted by PCS-Chris View Post
    When you run the CentOS installer just choose review/modify existing partition layout, by default it wont touch the existing filesystems. Just format / - obviously beforehand you need to backup /etc/vz/conf and any other configuration files you need.
    I think the other issue I have is if I use the remote installer at the datacentre to carry this out, it will automatically reformat the disk.
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  11. #11
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    Might do if its automated, I usually insist in having the full CentOS DVD in the machine + kvm access so I can do it all by hand

  12. #12
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    Quote Originally Posted by PCS-Chris View Post
    Might do if its automated, I usually insist in having the full CentOS DVD in the machine + kvm access so I can do it all by hand
    I guessed as much. Will see if the Datacentre are willing to put the DVD into the drive that without charging me (unlikely!)
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