FAQ
We've got about 200 existing servers running CentOS/RHEL 5.6 and all new
servers are being provisioned using CentOS/RHEL 6.1. So that everything
is consistent we need to upgrade the servers running CentOS/RHEL 5.6. I've
searched the CentOS wiki, the Red Hat site, and the internet looking for
something official on upgrading/migrating from CentOS/RHEL 5.x to
CentOS/RHEL 6.x. There's got to be a way other than having 2 times
hardware.

Any ideas???

Thanks,
Gene Poole

+ It's impossible for everything to be true. +

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  • Frank Cox at Jan 10, 2012 at 2:08 pm

    On Tue, 10 Jan 2012 13:55:05 -0500 Gene Poole wrote:

    We've got about 200 existing servers running CentOS/RHEL 5.6 and all new
    servers are being provisioned using CentOS/RHEL 6.1. So that everything
    is consistent we need to upgrade the servers running CentOS/RHEL 5.6. I've
    searched the CentOS wiki, the Red Hat site, and the internet looking for
    something official on upgrading/migrating from CentOS/RHEL 5.x to
    CentOS/RHEL 6.x. There's got to be a way other than having 2 times
    hardware.
    Backup your data/configurations, reformat, re-install your data/configurations.

    There is no other "official way" to change from v5 to v6.

    --
    MELVILLE THEATRE ~ Real D 3D Digital Cinema ~ www.melvilletheatre.com
    www.creekfm.com - FIFTY THOUSAND WATTS of POW WOW POWER!
  • Mark Roth at Jan 10, 2012 at 2:35 pm

    Gene Poole wrote:
    We've got about 200 existing servers running CentOS/RHEL 5.6 and all new
    servers are being provisioned using CentOS/RHEL 6.1. So that everything
    is consistent we need to upgrade the servers running CentOS/RHEL 5.6. I've
    searched the CentOS wiki, the Red Hat site, and the internet looking for
    something official on upgrading/migrating from CentOS/RHEL 5.x to
    CentOS/RHEL 6.x. There's got to be a way other than having 2 times
    hardware.

    Any ideas???
    What we do is build one, then create /boot/new and /new on the next
    server, rsync over to them, then mkdir /boot/old and /old, and (using zsh
    with modules loaded) mv * old, mv old/lost+found ., mv old/new/* ., make
    sure a few things are correct (for example, ifcfg-eth*, /etc/ssh/), and
    sync, then reboot. All your other stuff is fine....

    mark
  • Les Mikesell at Jan 10, 2012 at 4:16 pm

    On Tue, Jan 10, 2012 at 1:35 PM, wrote:
    We've got about 200 existing servers running CentOS/RHEL 5.6 and all new
    servers are being provisioned using CentOS/RHEL 6.1. ?So that everything
    is consistent we need to upgrade the servers running CentOS/RHEL 5.6. I've
    searched the CentOS wiki, the Red Hat site, and the internet ?looking for
    something official on upgrading/migrating from CentOS/RHEL 5.x to
    CentOS/RHEL 6.x. ?There's got to be a way other than having 2 times
    hardware.

    Any ideas???
    What we do is build one, then create /boot/new and /new on the next
    server, rsync over to them, then mkdir /boot/old and /old, and (using zsh
    with modules loaded) mv * old, mv old/lost+found ., mv old/new/* ., make
    sure a few things are correct (for example, ifcfg-eth*, /etc/ssh/), and
    sync, then reboot. All your other stuff is fine....
    Have you looked at http://rear.sourceforge.net/ (and in EPEL) as a
    potential backup/clone/rollout mechanism? It seems like something
    that might suit your sensibilities, but I'm not sure what kind of
    contortions you would need to do to boot into its recovery image
    remotely. For anyone too lazy to look, it builds a bootable iso
    containing your own current system's tools to re-install itself,
    recreating the filesystem (LVM/raid/partitions) and dropping in a
    backup that can be included or separate. It is intended for mostly
    automated restores back onto the same system but I think it can be
    abused for cloning and there is a point where you can adjust the
    filesystem layout.

    --
    Les Mikesell
    lesmikesell at gmail.com
  • Mark Roth at Jan 10, 2012 at 4:35 pm

    Les Mikesell wrote:
    On Tue, Jan 10, 2012 at 1:35 PM, wrote:

    We've got about 200 existing servers running CentOS/RHEL 5.6 and all
    new servers are being provisioned using CentOS/RHEL 6.1. ?So that
    everything is consistent we need to upgrade the servers running
    CentOS/RHEL 5.6.
    <snip>
    Any ideas???
    What we do is build one, then create /boot/new and /new on the next
    server, rsync over to them, then mkdir /boot/old and /old, and (using
    zsh with modules loaded) mv * old, mv old/lost+found ., mv
    old/new/* ., make sure a few things are correct (for example,
    ifcfg-eth*, /etc/ssh/), and sync, then reboot. All your other stuff is
    fine....
    Have you looked at http://rear.sourceforge.net/ (and in EPEL) as a
    potential backup/clone/rollout mechanism? It seems like something
    <snip>
    The one difference with the method we use is that you *don't* have to
    format /, and so anything you have under it is still safe. We normally
    have a few directories that are local, and so need to be saved (web, a
    temp that everyone can use that is guaranteed *not* to go away, etc).

    It's also pretty quick: you don't affect the running system while you're
    rsyncing over, so then the rotation takes long enough to issue the few
    commands, check grub and fstab, and reboot.

    mark
  • Les Mikesell at Jan 10, 2012 at 8:19 pm

    On Tue, Jan 10, 2012 at 3:35 PM, wrote:

    What we do is build one, then create /boot/new and /new on the next
    server, rsync over to them, then mkdir /boot/old and /old, and (using
    zsh with modules loaded) mv * old, mv old/lost+found ., mv
    old/new/* ., make sure a few things are correct (for example,
    ifcfg-eth*, /etc/ssh/), and sync, then reboot. All your other stuff is
    fine....
    Have you looked at http://rear.sourceforge.net/ (and in EPEL) as a
    potential backup/clone/rollout mechanism? ?It seems like something
    <snip>
    The one difference with the method we use is that you *don't* have to
    format /, and so anything you have under it is still safe. We normally
    have a few directories that are local, and so need to be saved (web, a
    temp that everyone can use that is guaranteed *not* to go away, etc).
    But that also means you don't get to re-arrange your filesystem layout
    to set up a bigger /boot, change filesystem types, or fix something
    you've learned could be better in the years of running the previous
    version.

    --
    Les Mikesell
    lesmikesell at gmail.com
  • Rushton Martin at Mar 12, 2012 at 2:08 pm
    I'm trying to configure an old 64-bit desktop machine as a client for a
    CentOS server. The client must have no modifiable storage at all so my
    options seem to be:
    1) Stateless network boot
    2) Live DVD

    I've been looking at the latter route, does anyone know if there is a
    convenient hook so that the live dvd will automatically download and
    execute a file during bootstrapping? I need to have some state, but
    held on the server. If there are any instructions for hacking the
    CentOS live dvd, please point me at them.

    I'd prefer not to go for a complete stateless network boot, the server
    will be booted in a number of configurations and it would mean
    reconfiguring xCAT or similar on each set of disks. Just to be even
    more awkward, there is no external network connection to the server,
    which will be running a 64-bit variant.

    Martin Rushton
    HPC System Manager, Weapons Technologies
    Tel: 01959 514777, Mobile: 07939 219057
    email: jmrushton at QinetiQ.com
    www.QinetiQ.com
    QinetiQ - Delivering customer-focused solutions
    This email and any attachments to it may be confidential and are
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    Park, Ively Road, Farnborough, Hampshire, GU14 0LX http://www.qinetiq.com.
  • Mark Roth at Mar 12, 2012 at 2:10 pm

    Rushton Martin wrote:
    I'm trying to configure an old 64-bit desktop machine as a client for a
    CentOS server. The client must have no modifiable storage at all so my
    options seem to be:
    1) Stateless network boot
    2) Live DVD

    I've been looking at the latter route, does anyone know if there is a
    convenient hook so that the live dvd will automatically download and
    execute a file during bootstrapping? I need to have some state, but
    held on the server. If there are any instructions for hacking the
    CentOS live dvd, please point me at them.
    Not CentOS, but perhaps you might be interested in LPS
    <http://www.spi.dod.mil/lipose.htm>

    No mounted storage at all, and built by a team from the US DoD, who
    *ought* to be paranoid enough for you. I've put it on a USB key, and have
    been saying for a month or so I need to try it (this would be for work,
    where I *have* to use a PIV "smart card" to get in from outside).

    mark
  • Johnny Hughes at Jan 11, 2012 at 8:17 am

    On 01/10/2012 12:55 PM, Gene Poole wrote:
    We've got about 200 existing servers running CentOS/RHEL 5.6 and all new
    servers are being provisioned using CentOS/RHEL 6.1. So that everything
    is consistent we need to upgrade the servers running CentOS/RHEL 5.6. I've
    searched the CentOS wiki, the Red Hat site, and the internet looking for
    something official on upgrading/migrating from CentOS/RHEL 5.x to
    CentOS/RHEL 6.x. There's got to be a way other than having 2 times
    hardware.

    Any ideas???
    Note, it does not take 2x the hardware ... you only need 1 extra machine
    to convert 1 server at a time from 5.x to 6.x and when you get done, use
    that do the next one. You can do more than one on a machine with VMs as
    well (or as suggested, backup, format and bring on data, reconfigure)

    You CAN (unsupported :D) also use a 6.x disc and run an upgrade over top
    the old machine. (It should offer that as an option for the install).
    But RH does not recommend or support upgrades done that way if using
    RHEL, so use at your own risk. Also please understand that things are
    not going to "just work" after an upgrade from CentOS 5.x to 6.x. For
    example, if you have php based websites using php-5.1.6-x in CentOS-5,
    you are likely going to have issues running them on php-5.3.x in CentOS-6.

    The bottom line is that CentOS provides 7 years of support, but moving
    between major versions requires that you reconfigure everything. You
    can still get support for CentOS-5.x through 31 Mar 2014, so you have
    time before you need to move those 5.x servers to 6.x.

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