Going from Centos 6 to Ubuntu Server
Michael Butash
michael at butash.net
Tue Mar 27 00:28:53 MST 2012
Well, most people don't bother or even know why they would unless
jockying servers. Most will just pop in _one_ hard disk, install linux,
and call it a day celebrating the imminent death of windoze. Until it
fails, they scratch their head, cry, and get another _one_, not
understanding two redundant disks are just a possibly easy to setup/use
and would have saved the hassle.
I've been playing with raids since the 90's where slowaris taught me
partitioning strategies. I forced myself to learn/use software raid
once linux became viable for me full-time with ubuntu. Once I found the
Ubuntu Alt cd circa 6.06 had recipies for raid/lvm already, it was a
no-brainer.
I use the alt disk exclusively for desktop to layer file systems, mostly
because I :
1) need redundancy (md),
2) need crypto (luks, work laptop roams with me, or not), and
3) need versatility (lvm, partitioning extends for those "wow, win7 is
really a pig wanting 25g for a silly vm, good thing I left free space on
the vg!" moments).
You have to use that really ugly and scary ncurses menu on Alt installs,
but after dozens of installs I can fly with it much more efficiently
than the full desktop, with way more rich disk features.
I'm surprised more linux users don't pay their desktops respect they
would a server with raid. It's almost as painful to toss a disk without
redundancy in a desktop as it is a production server, in may ways more.
MDadm has been more of a pain in recent years, but all in all it's
saved me at least 3 times on personal systems over the years from a
total loss, even though recovery isn't always so straight forward. Time
well spent to learn - good subject for a hackfest.
-mb
On 03/26/2012 11:45 PM, ChasM Marshall wrote:
> Wow!
>
> This is the first I've seen here that ANYONE is using a seperate /boot
> partition.
>
> I've been using one since about 2.2 kernels.
> I started out using 50Mb but, with Ubuntu and GRUB 2.0
> it needs around 300Mb to 500Mb. A Fedora 15 install didn't
> complain using a little as 150Mb. The minimum is for my
> Windows "ntldr" which requires only 50Mb.
>
> I've never needed LVMs or software raids for my desktop.
> As I understand it, they are not involved during boot, but are
> a requirement to access the newer GRUB config scripts in Ubuntu.
> Use a live boot disc, as Stephen says, to be sure they are accessable.
> Most of my (single-user) boxes have three to seven OSes to boot from.
> All within a less than 100Gb hard drive. I'm using Grub Legacy.
>
> If your Centos server is a large system, you may rather try this on a
> seperate hardware test machine, for safety. I've seen trouble from the
> Ubuntu GRUB scripts. Specifically, their "os_prober" has problems
> identifying other bootable kernels and systems when generating
> the new Ubuntu boot menu.
>
> Another problem is that Ubuntu is capable of GPT or MBR hard drives.
> MBR is the classic Master Boot Record.
> GPT is newer, larger, and demands specific hardware abilities.
> I've seen Win 7 using GPT, so caveat emptor.
>
> (-: Chas.M. :-)
>
> ------------------------------------------------------------------------
> Date: Wed, 21 Mar 2012 20:11:34 -0700
> Subject: Re: Going from Centos 6 to Ubuntu Server
> From: nadimhoque at gmail.com
> To: plug-discuss at lists.plug.phoenix.az.us
>
> Well with my setup I do have the boot partition separate from the LVM
> and the raid is pure software as far as I know. I was just asking if it
> was safe to do so. Unfortunately the boot partition is a bit on the
> smaller size at 100mb so I can easily fit around 2 kernels. I guess the
> other reason I am thinking to switch is because with Ubuntu, they have a
> predictable release schedule and with 12.04 LTS around the corner, I can
> get a server OS that is "stable" and up to date. I know I can compile
> from source all of the packages I have, like the the kernel and the
> software for the LAMP stack that I am also running.
>
> I also like the fact for the Ubuntu implementation of Samba; I can use
> the the system username and password instead of first creating a user on
> the system and again as a samba user. Other than that I do like Centos
> right now. Thanks for your help.
>
> On Wed, Mar 21, 2012 at 7:21 PM, Michael Butash <michael at butash.net
> <mailto:michael at butash.net>> wrote:
>
> Should be able to - depends how you're partitioned.
>
> I'm assuming your raid0 is done with mdadm and not fake-raid based.
>
> As long as your boot partition (non-lvm) is large enough to support
> enough kernels, you should be able to install over the system lv's
> you don't want, and not touch the ones that you do. Probably just
> create new lv's assuming you have the space for new root, usr, var,
> whatever you want. I usually create home without a separate
> partition, leaving alone the existing home, and simply mount the
> /home lv after reinstall "just in case".
>
> Note I've had some weirdness with ubuntu/mdadm depending what
> version mdadm metadata it was built with. In 11.04 I had to build
> md's specifically to use 0.90 metadata to work fully (i.e. reboot
> without having to busybox assemble md manually), 11.10 and higher I
> had to build the raid specifically with the current version
> (default) to work.
>
> I layered luks/lvm/ext4 atop this too, never did figure out exactly
> which was borking it, but the metadata was the trick for me. It also
> could have been related to my ssd alignment partitioning that always
> gave me grief with low-level fs.
>
> -mb
>
>
>
> On 03/21/2012 03:19 PM, Stephen wrote:
>
> if it boots up and sees the LVM then you should be able to customer
> partition and configure without reformatting.
>
> you can look and see a fair amount without even writing changes
> to the disk.
>
> However i would still make a backup.
>
> On Wed, Mar 21, 2012 at 1:55 PM, Nadim
> Hoque<nadimhoque at gmail.com <mailto:nadimhoque at gmail.com>> wrote:
>
> I currently have Centos 6 installed with software raid 0
> with LVM. I was
> wondering if it is possible to install Ubuntu server 10.04
> with those
> settings without data loss and that the current raid/lvm
> will stay in tact.
> So far in my experience I should be able to do this, but I
> just wanted your
> input on the matter. I might switch to ubuntu server for the
> vast number of
> packages in the default repos and when I used it before I
> really liked it (I
> love how the default repos have what I want, and ufw is nice
> as well).
>
> --
> Nadim Hoque
> Undergraduate Intern
> ASU Advanced Computing Center
> Cell: 480-518-6235
>
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> --
> Nadim Hoque
> Undergraduate Intern
> ASU Advanced Computing Center
> Cell: 480-518-6235
>
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