OT:Linux question

[Brian K. White]

On 11/22/2010 9:32 AM, Boaz Bezborodko wrote:
>
>> Date: Sun, 21 Nov 2010 13:25:47 -0500
>> From: Fairlight<fairlite at fairlite.com>
>> Subject: Re: OT:Linux question
>> To: filepro-list at lists.celestial.com
>> Message-ID:<20101121132547.A15495 at iglou.com>
>> Content-Type: text/plain; charset=us-ascii
>>
>> On Sun, Nov 21, 2010 at 11:53:36AM -0500, after drawing runes in goat's blood,
>> Boaz Bezborodko cast forth these immortal, mystical words:
>>> While I risk angering Mark for an OT question on Linux, I trust you guys
>>> the most on these issues.
>> My lord, man!  How -could- you?!?!?  :) :) :)
>>
>
> Hey...I'm still sensitive about how you flamed me 3 years ago when I
> first started using Linux and was asking some basic questions.
>
>>> I have a question regarding expanding storage on Linux.  I have an old
>>> Proliant system running Centos 4 with a raid array.  I've replaced older
>>> 73GB drives with 146GB drives and I wanted to extend the volume size.
>>> The HP Array Cofiguration Utility is giving me a warning that some OSes
>>> don't support "extending" the volume and that this might make the data
>>> unavailable to them.
>>>
>>> Will LVM on Centos 4 recognize this and be able to increase the volume?
>>>
>>> If yes, should I dismount the volume before running the operation?
>> http://tldp.org/HOWTO/LVM-HOWTO/extendlv.html
>> http://www.brighthub.com/computing/linux/articles/48452.aspx
>> http://www.softpanorama.org/Commercial_linuxes/logical_volume_manager.shtml
>>
>> The last one covers RHEL4, which is largely the same codebase as CentOS 4,
>> except CentOS has RH's insane bugs removed.  :)
>>
>> Funny, I thought everyone knew about Google by now...
>>
>> mark->
>
> I figured that part out even though I didn't need to.  Webmin can do
> this all easily.
>
> The question is whether Centos 4 will recognize the extra space after I
> extend the size of the existing logical drive using the HP array
> utility.  If not then I have to add the extra space as another logical
> drive and tell LVM to add it as a new physical volume before extending
> the volume size.
>
> I was hoping that someone on this list, given the vast amount of Linux
> experience some people (like yourself) have, that this is something that
> can be answered easily.

His point was that "linux experts" don't just know everything, they use 
google, even when they do happen to know something because the details 
often change.

Linux expertise does not answer a question like that directly. Even if 
you happened to have done exactly that same task before, chances are 
some of the details have changed since last time you did it, so you'd 
still need to start by looking it all up, not by thinking you're a linux 
expert and already know.

Linux expertise says things like don't use lvm unless necessary, (which 
necessarily means learning what lvm is and does and what it's drawbacks 
are so that you can even decide if it's necessary or not).

Linux expertise says things like you can use webmin if you like on your 
box, but I won't have it installed on mine.

Linux expertise says here's how you go about answering any question like 
that:
* Determine all involved version numbers and context info, what 
platform, what distribution, what version of the distribution, what 
version of linux kernel, what version of any lvm utilities.
* Google up the manuals for lvm and try to find info specifically for 
those versions.
* Determine what kind of filesystem you have, and google up if it's even 
possible to resize that type of filesystem, because not all are 
resizable, and some are resizable only after certain versions, and some 
are unsafe to resize even though it's supposed to be possible.

Linux expertise helps you filter the garbage from all the google results 
and spot the patterns that show "it's mostly idiots who say X, and 
mostly knowledgeable who say Y"

And finally Linux expertise says whatever you google up, no matter how 
appropriate it seems, exactly matching all your details and seeming to 
come from "good" sources, you still don't do anything without looking up 
each suggested action and working out exactly what it will do, and 
agreeing with it's appropriateness for your particular situation.

Actually, before any of that, Linux expertise says reshaping a raid 
array and resizing a filesystem are both risky at best, and probably 
unnecessary, and thus unwise. Linux expertise says it's much safer, 
easier, simpler, not to mention faster, to just add a new filesystem, 
move some big directory to it, and rename the mount point to take the 
place of the directory the data originally came from, if there is any 
such directory where the data is a suitable size and grows at a suitable 
rate to make this practical.

-- 
bkw