[linux-lvm] where do i find the device mapper/LVM2 documentation?

[linux-lvm] where do i find the device mapper/LVM2 documentation?

[Jon Bendtsen]

Hi there, i'm looking for documentation for the device mapper/lvm2 in 
the linux 2.5/6 kernel.



JonB

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Joe Thornber]

On Tue, May 27, 2003 at 11:26:22AM +0200, Jon Bendtsen wrote:
> Hi there, i'm looking for documentation for the device mapper/lvm2 in 
> the linux 2.5/6 kernel.

i) Enable dm in the kernel config.
ii) Install libdevmapper from the latest device-mapper release at www.sistina.com
iii) Install LVM2 tools.

There is more documentation in the device-mapper and LVM2 packages.

- Joe

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Jon Bendtsen]

Joe Thornber wrote:
> On Tue, May 27, 2003 at 11:26:22AM +0200, Jon Bendtsen wrote:
> 
>>Hi there, i'm looking for documentation for the device mapper/lvm2 in 
>>the linux 2.5/6 kernel.
> 
> 
> i) Enable dm in the kernel config.
> ii) Install libdevmapper from the latest device-mapper release at www.sistina.com
> iii) Install LVM2 tools.
> 
> There is more documentation in the device-mapper and LVM2 packages.

i downloaded devicemapper.?.98?.tar.gz or something (the latest one) and 
i dont find much documentation in that, though i have looked into the 
INTRO file i didnt find others that from name appeared to be documentation.




JonB

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Joe Thornber]

On Tue, May 27, 2003 at 12:27:48PM +0200, Jon Bendtsen wrote:
> Joe Thornber wrote:
> >On Tue, May 27, 2003 at 11:26:22AM +0200, Jon Bendtsen wrote:
> >
> >>Hi there, i'm looking for documentation for the device mapper/lvm2 in 
> >>the linux 2.5/6 kernel.
> >
> >
> >i) Enable dm in the kernel config.
> >ii) Install libdevmapper from the latest device-mapper release at 
> >www.sistina.com
> >iii) Install LVM2 tools.
> >
> >There is more documentation in the device-mapper and LVM2 packages.
> 
> i downloaded devicemapper.?.98?.tar.gz or something (the latest one) and 
> i dont find much documentation in that, though i have looked into the 
> INTRO file i didnt find others that from name appeared to be documentation.

What exactly do you want to know ?

- Joe

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Debian User]

On Tue, May 27, 2003 at 11:49:59AM +0100, Joe Thornber wrote:
> On Tue, May 27, 2003 at 12:27:48PM +0200, Jon Bendtsen wrote:
> > Joe Thornber wrote:
> > >On Tue, May 27, 2003 at 11:26:22AM +0200, Jon Bendtsen wrote:
> > >
> > >>Hi there, i'm looking for documentation for the device mapper/lvm2 in 
> > >>the linux 2.5/6 kernel.
> > >
> > >
> > >i) Enable dm in the kernel config.
> > >ii) Install libdevmapper from the latest device-mapper release at 
> > >www.sistina.com
> > >iii) Install LVM2 tools.
> > >
> > >There is more documentation in the device-mapper and LVM2 packages.
> > 
> > i downloaded devicemapper.?.98?.tar.gz or something (the latest one) and 
> > i dont find much documentation in that, though i have looked into the 
> > INTRO file i didnt find others that from name appeared to be documentation.
> 
> What exactly do you want to know ?

How it is built up. Detailed information explaining to me how i can expand
it, stuff like that. The LVM1 howto has a part that describes how the LVM1
is built up piece by piece, Physical Volumes, Physical Extends, ...




JonB

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Joe Thornber]

On Wed, May 28, 2003 at 12:09:01AM +0200, Debian User wrote:
> On Tue, May 27, 2003 at 11:49:59AM +0100, Joe Thornber wrote:
> > On Tue, May 27, 2003 at 12:27:48PM +0200, Jon Bendtsen wrote:
> > > Joe Thornber wrote:
> > > >On Tue, May 27, 2003 at 11:26:22AM +0200, Jon Bendtsen wrote:
> > > >
> > > >>Hi there, i'm looking for documentation for the device mapper/lvm2 in 
> > > >>the linux 2.5/6 kernel.
> > > >
> > > >
> > > >i) Enable dm in the kernel config.
> > > >ii) Install libdevmapper from the latest device-mapper release at 
> > > >www.sistina.com
> > > >iii) Install LVM2 tools.
> > > >
> > > >There is more documentation in the device-mapper and LVM2 packages.
> > > 
> > > i downloaded devicemapper.?.98?.tar.gz or something (the latest one) and 
> > > i dont find much documentation in that, though i have looked into the 
> > > INTRO file i didnt find others that from name appeared to be documentation.
> > 
> > What exactly do you want to know ?
> 
> How it is built up. Detailed information explaining to me how i can expand
> it, stuff like that. The LVM1 howto has a part that describes how the LVM1
> is built up piece by piece, Physical Volumes, Physical Extends, ...

LVM2 uses the same model, the difference is it uses dm to implement
it.  Read the dmsetup man page for more info on how dm works.

- Joe

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Jon Bendtsen]

Joe Thornber wrote:
> On Wed, May 28, 2003 at 12:09:01AM +0200, Debian User wrote:
> 
>>On Tue, May 27, 2003 at 11:49:59AM +0100, Joe Thornber wrote:

[cut]


>>>What exactly do you want to know ?
>>
>>How it is built up. Detailed information explaining to me how i can expand
>>it, stuff like that. The LVM1 howto has a part that describes how the LVM1
>>is built up piece by piece, Physical Volumes, Physical Extends, ...
> 
> 
> LVM2 uses the same model, the difference is it uses dm to implement
> it.  Read the dmsetup man page for more info on how dm works.

Okay? thats not the impression i got from reading what documentation i 
could find (INTRO and dmsetup.8).



JonB

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Joe Thornber]

On Wed, May 28, 2003 at 10:52:49AM +0200, Jon Bendtsen wrote:
> Okay? thats not the impression i got from reading what documentation i 
> could find (INTRO and dmsetup.8).

The driver is very different, but the userland tools still have
exactly the same concepts of extents, PVs, LVs and VGs.  The LVM2
tools have a few extra features, but other than that they are
identical in use to the LVM1 ones.

- Joe

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Jason H. Smith]

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> >>How it is built up. Detailed information explaining to me how i can
> >> expand it, stuff like that.

May I suggest the source code?

-- 
Jason Smith
Open Enterprise Systems
Bangkok, Thailand

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Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Daniel Phillips]

On Wednesday 28 May 2003 11:42, Jason H. Smith wrote:
> > >>How it is built up. Detailed information explaining to me how i can
> > >> expand it, stuff like that.
>
> May I suggest the source code?

One can always suggest the source code, and without understating the value of 
that, we can and will do better.

Regards,

Daniel

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Debian User]

On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
> On Wednesday 28 May 2003 11:42, Jason H. Smith wrote:
> > > >>How it is built up. Detailed information explaining to me how i can
> > > >> expand it, stuff like that.
> >
> > May I suggest the source code?
> 
> One can always suggest the source code, and without understating the value of 
> that, we can and will do better.

I'm sorry, you lost me somewhere? I dont mind looking at the code, but
other documentation is nice too.



JonB

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Daniel Phillips]

On Thursday 29 May 2003 20:38, Debian User wrote:
> On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
> > On Wednesday 28 May 2003 11:42, Jason H. Smith wrote:
> > > > >>How it is built up. Detailed information explaining to me how i can
> > > > >> expand it, stuff like that.
> > >
> > > May I suggest the source code?
> >
> > One can always suggest the source code, and without understating the
> > value of that, we can and will do better.
>
> I'm sorry, you lost me somewhere? I dont mind looking at the code, but
> other documentation is nice too.

Sorry if I wasn't clear.  We're violently agreeing.

Regards,

Daniel

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Joe Thornber]

On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
> On Wednesday 28 May 2003 11:42, Jason H. Smith wrote:
> > > >>How it is built up. Detailed information explaining to me how i can
> > > >> expand it, stuff like that.

If you're interested in writing your own targets I suggest you look at
a couple of the trivial targets that already exist.  Such as
dm-linear.c, dm-stripe.c.

- Joe

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[jon+lvm]

On Thu, May 29, 2003 at 10:21:27PM +0100, Joe Thornber wrote:
> On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
> > On Wednesday 28 May 2003 11:42, Jason H. Smith wrote:
> > > > >>How it is built up. Detailed information explaining to me how i can
> > > > >> expand it, stuff like that.
> 
> If you're interested in writing your own targets I suggest you look at
> a couple of the trivial targets that already exist.  Such as
> dm-linear.c, dm-stripe.c.

i am planning to write my own targets as a graduate project.
My idea was encryption and possibly compression as well.
(is anyone else doing any of these targets?)


JonB

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Daniel Phillips]

On Friday 30 May 2003 00:02, jon+lvm@silicide.dk wrote:
> On Thu, May 29, 2003 at 10:21:27PM +0100, Joe Thornber wrote:
> > On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
> > > On Wednesday 28 May 2003 11:42, Jason H. Smith wrote:
> > > > > >>How it is built up. Detailed information explaining to me how i
> > > > > >> can expand it, stuff like that.
> >
> > If you're interested in writing your own targets I suggest you look at
> > a couple of the trivial targets that already exist.  Such as
> > dm-linear.c, dm-stripe.c.
>
> i am planning to write my own targets as a graduate project.
> My idea was encryption and possibly compression as well.
> (is anyone else doing any of these targets?)

Not as far as I know - it's considered good though.

Regards,

Daniel

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[jon+lvm]

On Fri, May 30, 2003 at 12:54:07AM +0200, Daniel Phillips wrote:
> On Friday 30 May 2003 00:02, jon+lvm@silicide.dk wrote:
> > On Thu, May 29, 2003 at 10:21:27PM +0100, Joe Thornber wrote:
> > > On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
> > > > On Wednesday 28 May 2003 11:42, Jason H. Smith wrote:
> > > > > > >>How it is built up. Detailed information explaining to me how i
> > > > > > >> can expand it, stuff like that.
> > >
> > > If you're interested in writing your own targets I suggest you look at
> > > a couple of the trivial targets that already exist.  Such as
> > > dm-linear.c, dm-stripe.c.
> >
> > i am planning to write my own targets as a graduate project.
> > My idea was encryption and possibly compression as well.
> > (is anyone else doing any of these targets?)
> 
> Not as far as I know - it's considered good though.

What is considered good ?



JonB

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Daniel Phillips]

On Friday 30 May 2003 09:22, jon+lvm@silicide.dk wrote:
> On Fri, May 30, 2003 at 12:54:07AM +0200, Daniel Phillips wrote:
> > On Friday 30 May 2003 00:02, jon+lvm@silicide.dk wrote:
> > > i am planning to write my own targets as a graduate project.
> > > My idea was encryption and possibly compression as well.
> > > (is anyone else doing any of these targets?)
> >
> > Not as far as I know - it's considered good though.
>
> What is considered good ?

Implementing an encrypting or compressing block device as a device-mapper 
target.  It's been discussed, but as far as I know, nobody has started on it.

Regards,

Daniel

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Joe Thornber]

On Fri, May 30, 2003 at 12:02:39AM +0200, jon+lvm@silicide.dk wrote:
> i am planning to write my own targets as a graduate project.
> My idea was encryption and possibly compression as well.
> (is anyone else doing any of these targets?)

This is an idea that quite a few people have come up with, but as far
as I know nobody is following up on it.  I'd suggest you start with
the encryption target, I think that's slightly easier since you can
arrange for the encrypted data to be the same size as clear.  You
should then use the end_io() method to catch the buffer_heads after
they've read the encrypted data and decrypt it there.  The dm side
should be very simple, yell if you have any questions.

- Joe

re[2]: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Greg Freemyer]

 >>  On Thu, May 29, 2003 at 10:21:27PM +0100, Joe Thornber wrote:
 >>  > On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
 >>  > 
 >>  > If you're interested in writing your own targets I suggest you look at
 >>  > a couple of the trivial targets that already exist.  Such as
 >>  > dm-linear.c, dm-stripe.c.

 >>  i am planning to write my own targets as a graduate project.
 >>  My idea was encryption and possibly compression as well.
 >>  (is anyone else doing any of these targets?)

An encrypting target would be nice, but does it offer any value over an encrypting loopback device?

(I assume LVM2 is compatible with the existing loopback encrypting devices.)

A compressing target would be uniquely valuable because I don't think it can be implemented via a loopback device.

i.e. I believe a loopback device requires a 1:1 (or constant) ratio between input size and output size.

Actually, that sounds like a pretty interesting problem to try to work on.  

Greg
-- 
Greg Freemyer

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Joe Thornber]

On Fri, May 30, 2003 at 01:22:32PM -0400, Greg Freemyer wrote:
>  >>  On Thu, May 29, 2003 at 10:21:27PM +0100, Joe Thornber wrote:
>  >>  > On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
>  >>  > 
>  >>  > If you're interested in writing your own targets I suggest you look at
>  >>  > a couple of the trivial targets that already exist.  Such as
>  >>  > dm-linear.c, dm-stripe.c.
> 
>  >>  i am planning to write my own targets as a graduate project.
>  >>  My idea was encryption and possibly compression as well.
>  >>  (is anyone else doing any of these targets?)
> 
> An encrypting target would be nice, but does it offer any value over an encrypting loopback device?

I still don't trust the loop device enough to use it.

- Joe

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Luca Berra]

On Fri, May 30, 2003 at 06:23:55PM +0100, Joe Thornber wrote:
>On Fri, May 30, 2003 at 01:22:32PM -0400, Greg Freemyer wrote:
>> An encrypting target would be nice, but does it offer any value over an encrypting loopback device?
>
>I still don't trust the loop device enough to use it.
well.
i have been using loop-AES on my laptop for over 1 year and i am
satisfied with it.
said that, if having encryption as a dm target would mean havig a single
interface for device mapping, it would certainly be the best thing.

-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
 /"\
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  X        AGAINST HTML MAIL
 / \

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[jon+lvm]

On Fri, May 30, 2003 at 06:23:55PM +0100, Joe Thornber wrote:
> On Fri, May 30, 2003 at 01:22:32PM -0400, Greg Freemyer wrote:
> >  >>  On Thu, May 29, 2003 at 10:21:27PM +0100, Joe Thornber wrote:
> >  >>  > On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
> >  >>  > 
> >  >>  > If you're interested in writing your own targets I suggest you look at
> >  >>  > a couple of the trivial targets that already exist.  Such as
> >  >>  > dm-linear.c, dm-stripe.c.
> > 
> >  >>  i am planning to write my own targets as a graduate project.
> >  >>  My idea was encryption and possibly compression as well.
> >  >>  (is anyone else doing any of these targets?)
> > 
> > An encrypting target would be nice, but does it offer any value over an encrypting loopback device?
> 
> I still don't trust the loop device enough to use it.

Why not?
What makes you think you will trust an encryption target that also
uses cryptoAPI?



JonB

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Joe Thornber]

On Sat, May 31, 2003 at 11:08:33AM +0200, jon+lvm@silicide.dk wrote:
> Why not?

because it deadlocks when testing under load.

- Joe

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[Daniel Phillips]

On Friday 30 May 2003 19:22, Greg Freemyer wrote:
>  >>  On Thu, May 29, 2003 at 10:21:27PM +0100, Joe Thornber wrote:
>  >>  > On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
>  >>  >
>  >>  > If you're interested in writing your own targets I suggest you look
>  >>  > at a couple of the trivial targets that already exist.  Such as
>  >>  > dm-linear.c, dm-stripe.c.
>  >>
>  >>  i am planning to write my own targets as a graduate project.
>  >>  My idea was encryption and possibly compression as well.
>  >>  (is anyone else doing any of these targets?)
>
> An encrypting target would be nice, but does it offer any value over an
> encrypting loopback device?

Simplicity and reliability?

Regards,

Daniel

Re: [linux-lvm] where do i find the device mapper/LVM2 documentation?

[jon+lvm]

On Fri, May 30, 2003 at 01:22:32PM -0400, Greg Freemyer wrote:
>  >>  On Thu, May 29, 2003 at 10:21:27PM +0100, Joe Thornber wrote:
>  >>  > On Thu, May 29, 2003 at 02:27:15PM +0200, Daniel Phillips wrote:
>  >>  > 
>  >>  > If you're interested in writing your own targets I suggest you look at
>  >>  > a couple of the trivial targets that already exist.  Such as
>  >>  > dm-linear.c, dm-stripe.c.
> 
>  >>  i am planning to write my own targets as a graduate project.
>  >>  My idea was encryption and possibly compression as well.
>  >>  (is anyone else doing any of these targets?)
> 
> An encrypting target would be nice, but does it offer any value over an encrypting loopback device?

yes it does, or atleast so with the old LVM. Here at work i run
LVM ontop of loop-aes, and PPDD ontop of LVM (different machines)

bad:
loop-aes can not change password
you encrypt the hole LVM-system
ppdd can change password, but LVM1 wont run ontop of that, and still, you
have to encrypt everything
snapshots doesnt work when you puut loop-back ontop of a LV,
unless you unmount.


> (I assume LVM2 is compatible with the existing loopback encrypting devices.)

it does work, but there are some issues


> A compressing target would be uniquely valuable because I don't think it can be implemented via a loopback device.
> 
> i.e. I believe a loopback device requires a 1:1 (or constant) ratio between input size and output size.


knoppix has a read-only encryption loop-back device. I've talked with
my fellow students about writeable encryption, and they thought that
it would be like audio/video codecs, where you also cant map an address
in the system after to an address in the system before. (sector in data
to sector in compressed data). So they thought that adding indexes would
handle the problem that you cant know how much space data takes after
compression.


> Actually, that sounds like a pretty interesting problem to try to work on.  

yeah, i guess so



JonB