LVM-Howto [Was : what are the restrictions on bootable partitions?]

[neil]

mr700 at globalnet.bg wrote:

>On Friday 30 April 2004 05:11, Ow Mun Heng wrote:
>  
>
>>>-----Original Message-----
>>>From: neil [mailto:neilcuk at aol.com]
>>>Sent: Thursday, April 29, 2004 10:35 PM
>>>To: For users of Fedora Core releases
>>>Subject: Re: what are the restrictions on bootable partitions?
>>>
>>>
>>>
>>>
>>>rpjday at mindspring.com wrote:
>>>
>>>      
>>>
>>>> what are the restrictions on where i can install another 
>>>>        
>>>>
>>>linux distro
>>>      
>>>
>>>>onto my fedora core (actually, FC2-t3) system so that grub 
>>>>        
>>>>
>>>can find it?
>>>      
>>>
>>>>(even though this is a test version of fedora, this question actually
>>>>refers to FC distros in general.)
>>>> 
>>>>
>>>>        
>>>>
>>>There are no restrictions other than the boot loader (grub) 
>>>must be able 
>>>to read the boot partition.
>>>
>>>      
>>>
>>>> typically, for historical reasons, even when i use LVM, i 
>>>>        
>>>>
>>>create a small
>>>      
>>>
>>>>primary, ext3 filesystem for /boot, and use LVM for the rest 
>>>>        
>>>>
>>>of the drive.
>>>      
>>>
>>>>is there any compelling reason for doing this anymore?  what's the 
>>>>recommended strategy for LVM?  and need for a non-LVM 
>>>>        
>>>>
>>>filesystem on newer
>>>      
>>>
>>>>machines?
>>>>
>>>>        
>>>>
>>>It really depends on what the system will be used for. Check out the 
>>>howto here: http://www.tldp.org/HOWTO/LVM-HOWTO/index.html
>>>      
>>>
>>I've actually looked through the howto but am still unable to determine
>>how to actually create a lvm system. I've recompiled my kernel to 
>>have the devive mapper as a module and modprobe'ed it.
>>
>>When I try to do vgscan it states that the kernel modules are not loaded.
>>    
>>
>    I don't remember how I did this with RH9 to make it work, but I remember
>I played a bit whth modprobe, the LVM tools and the man pages :)
>  
>
>>Please help.
>>    
>>
>http://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/sysadmin-guide/ch-lvm.html
>http://www.redhat.com/docs/manuals/enterprise/RHEL-3-Manual/sysadmin-guide/ch-lvm-intro.html
>http://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/custom-guide/ch-lvm.html
>http://www.redhat.com/docs/manuals/linux/RHL-8.0-Manual/custom-guide/ch-lvm-intro.html
>http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/custom-guide/ch-lvm-intro.html
>...
>    I did install FC1 with Software Raid 5 and LVM on top of it, but doing so on less
>than three physical disks results to up to 5 times slower transfer (because of the
>raid). If you have 3 disks read speed increases and the write speed is almost the
>same. Using ReiserFS I was able to resize 61G LV to 64G LV without errors. With
>ext3 it worked, but fsck.ext3 had a lot of work to do (the partition was ~50G full).
>I hope one day online resize will work with bouth and reiserfs will get more stable
>with acl and SELinux support.
>    http://www.aplawrence.com/Linux/lvm.html
>    ps: putting the /boot partiton ouside the LVM worked fine for me.
>
>  
>
okay - there are a few steps one needs to take to get their system using 
LVM. It can be tricky to get your brain around at first but it will slot 
into place. The steps are quite straight forward - even when setting up 
post install. Here's a brief overview. I'm assuming you can follow the 
man pages of each of the commands specified - there are a number of 
options which will be up to you:

as root
One(a): Make sure you have backed up any important data before trashing 
your system ;-)
One: make sure your kernel supports LVM (By default this is supported in 
FC1)
Two: create some LVM partitions (of type 8e under fdisk)
Three: reboot or execute partprobe
Four: execute vgscan
Five: use pvcreate to assign your newly typed disks as use within the LVM
(actually, four and five might be back to front)
Six: use vgcreate to generate a new volume group (and add some physical 
volumes tro it)
Seven: use lvcreate to make your logical volume
Eight: format your new logical volume

then it's up to you - mount as you like

use e2fsadm to extend and reduce the size of the volume

There is a huge amount of documentation and you should really get to 
grips with resizing, adding new PVs etc. Before you start putting useful 
data on your new LV!

hope this provides some guidance.

neil