Going from Centos 6 to Ubuntu Server

Tue Mar 27 00:33:44 MST 2012

Yes, RAID 1 does seem like a minimum requirement anymore. 
Phil Waclawski 

----- Original Message -----

From: "Michael Butash" <michael at butash.net> 
To: plug-discuss at lists.plug.phoenix.az.us 
Sent: Tuesday, March 27, 2012 12:28:53 AM 
Subject: Re: Going from Centos 6 to Ubuntu Server 

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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