[linux-lvm] LVM rootfs and cramfs as ramdisk

[linux-lvm] LVM rootfs and cramfs as ramdisk

[Jan H. van Gils]

	Hi,

First some thinks I found out.

When you create with lvmcreate_initrd the /boot/initrd-lvm-<kernel> file
the file is an ext2 filesystem. On a debian distro that wil give you problems
because the kernel expects a cramfs as ramdisk file.

Here is a work around I found :

mount the /boot/initrd-lvm-<kernel> file
mount -t ext2 -o loop /boot/initrd-lvm-<kernel> /mnt

copy the file to temporary working directory
cd /mnt; find . -print | cpio -udmp /var/tmp/lvm

dismount the /mnt file system and mount the kernel original
mount -t cramfs -o loop /boot/initrd.img-<kernel>
cd /mnt; find . -print | cpio -udmp /var/tmp/lvm

now create the new cramfs initrd file
cd /var/tmp; mkcramfs lvm/ initrd.cramfs
make sure the owner and group member are root <chown -R root:root initrd.cramfs)

To be sure you can check the initrd.cramfs with cramfsck -v initrd.cramfs.

Now I am wondering about one thing ? cramfs is a readonly filesystem
when the system boot it executes a vgscan and that creates a
"/etc/lvmtab" and "/etc/lvmtab.d" successfully created".

But because the cramfs is readonly, wil this not be an impossibility,
and is the cramfs ramdisk file not possible@all !!

Please responce on this subject.

Greetz, Jan


-- 
With regards Jan H. van Gils
Internet web-page http://www.VGNet.NL/
Internet e-mail address JanVG@VGNet.NL
RIPE Whois JHG5-RIPE, 6BONE Whois JHG1-6BONE

Re: [linux-lvm] LVM rootfs and cramfs as ramdisk

[Francis SOUYRI]

Hi Jan,

You need "/etc" in rw for this you can mount "/etc" in the "linuxrc" 
script using a tmpfs filesystem like this:

/#!/bin/sh
...
mount -t tmpfs none /etc
mount -t proc none /proc
echo "Scanning for Volume Groups..."
/sbin/vgscan
echo "Activating Volume Groups"
/sbin/vgchange -a y
...
umount /proc
umount /etc
/
I used "romfs" for the "initrd" ramdisk.

Best regards.

Francis

Jan H. van Gils wrote:

>	Hi,
>
>First some thinks I found out.
>
>When you create with lvmcreate_initrd the /boot/initrd-lvm-<kernel> file
>the file is an ext2 filesystem. On a debian distro that wil give you problems
>because the kernel expects a cramfs as ramdisk file.
>
>Here is a work around I found :
>
>mount the /boot/initrd-lvm-<kernel> file
>mount -t ext2 -o loop /boot/initrd-lvm-<kernel> /mnt
>
>copy the file to temporary working directory
>cd /mnt; find . -print | cpio -udmp /var/tmp/lvm
>
>dismount the /mnt file system and mount the kernel original
>mount -t cramfs -o loop /boot/initrd.img-<kernel>
>cd /mnt; find . -print | cpio -udmp /var/tmp/lvm
>
>now create the new cramfs initrd file
>cd /var/tmp; mkcramfs lvm/ initrd.cramfs
>make sure the owner and group member are root <chown -R root:root initrd.cramfs)
>
>To be sure you can check the initrd.cramfs with cramfsck -v initrd.cramfs.
>
>Now I am wondering about one thing ? cramfs is a readonly filesystem
>when the system boot it executes a vgscan and that creates a
>"/etc/lvmtab" and "/etc/lvmtab.d" successfully created".
>
>But because the cramfs is readonly, wil this not be an impossibility,
>and is the cramfs ramdisk file not possible at all !!
>
>Please responce on this subject.
>
>Greetz, Jan
>
>
>  
>

RE: [linux-lvm] LVM rootfs and cramfs as ramdisk

[Jan H. van Gils]

>
>Hi Jan,

Hi Francis,

>
>You need "/etc" in rw for this you can mount "/etc" in the "linuxrc" 
>script using a tmpfs filesystem like this:
>

Thanks for the information.
I was already wondering if I was the only one with this problem.

But what about the init files that are normaly in "/etc" ?
I can imagion that a tmpfs is an empty filesystem.
Or do I not fully understand what you mount option does ?

>/#!/bin/sh
>...
>mount -t tmpfs none /etc
>mount -t proc none /proc
>echo "Scanning for Volume Groups..."
>/sbin/vgscan
>echo "Activating Volume Groups"
>/sbin/vgchange -a y
>...
>umount /proc
>umount /etc
>/
>I used "romfs" for the "initrd" ramdisk.
>
>Best regards.
>
>Francis
>

With regards Jan


----
With regards Jan H. van Gils
Internet web-page http://www.Knoware.NL/users/janvg/
Internet e-mail address JanVG@Knoware.NL
RIPE Whois JHG5-RIPE, 6BONE Whois JHG1-6BONE

Re: [linux-lvm] LVM rootfs and cramfs as ramdisk

[Francis SOUYRI]

Hi Jan,

On my system lvm driver is in the kernel (no module).

/#!/bin/sh

I mount /etc with a tmpfs to have /etc in rw (I do not need the 
"/etc/fstab").

mount -t tmpfs none /etc

Now I mount /proc because "vgscan" need to access "/proc/partitions" (I 
do not need the "/etc/fstab").

mount -t proc none /proc

Finaly I can scan for the volume groups and activate these volume groups.

echo "Scanning for Volume Groups..."
/sbin/vgscan
echo "Activating Volume Groups"
/sbin/vgchange -a y

I umount /proc and /etc because, I do not need now the "/etc" (you need 
to do a vgscan in the startup script of your system to update the 
"/etc/lvm*" files in the real "/etc"), and the kernel after the mount of 
the real / mount the /proc.

umount /proc
umount /etc

I do not need any files in the "/etc" I only need to create temporaries 
files with vgscan.

Best regards.

Francis

Jan H. van Gils wrote:

>>Hi Jan,
>>    
>>
>
>Hi Francis,
>
>  
>
>>You need "/etc" in rw for this you can mount "/etc" in the "linuxrc" 
>>script using a tmpfs filesystem like this:
>>
>>    
>>
>
>Thanks for the information.
>I was already wondering if I was the only one with this problem.
>
>But what about the init files that are normaly in "/etc" ?
>I can imagion that a tmpfs is an empty filesystem.
>Or do I not fully understand what you mount option does ?
>
>  
>
>>/#!/bin/sh
>>...
>>mount -t tmpfs none /etc
>>mount -t proc none /proc
>>echo "Scanning for Volume Groups..."
>>/sbin/vgscan
>>echo "Activating Volume Groups"
>>/sbin/vgchange -a y
>>...
>>umount /proc
>>umount /etc
>>/
>>I used "romfs" for the "initrd" ramdisk.
>>
>>Best regards.
>>
>>Francis
>>
>>    
>>
>
>With regards Jan
>
>
>----
>With regards Jan H. van Gils
>Internet web-page http://www.Knoware.NL/users/janvg/
>Internet e-mail address JanVG@Knoware.NL
>RIPE Whois JHG5-RIPE, 6BONE Whois JHG1-6BONE
>
>
>_______________________________________________
>linux-lvm mailing list
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>read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
>  
>