Re: [OxLUG] Raw devices

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Author: Oleg Buklanov
Date:  
To: Oxfordshire Linux User Group Discussion List
Subject: Re: [OxLUG] Raw devices
Hi!

As far as I remember raw device driver is obsolete on linux, because
applications can now use O_DIRECT flag.
If you want to perform unbuffered IO with dd, you can use options
iflag=direct and/or oflag=direct.


On Tue, Oct 25, 2011 at 6:29 PM, Sad Clouds <
> wrote:

> On Tue, 25 Oct 2011 16:46:42 +0100
> John Winters <> wrote:
>
> > On 25/10/11 15:15, Sad Clouds wrote:
> > > Hi, I'd like to backup entire partition (/dev/sda1) with dd. I don't
> > > see any raw devices under /dev, so is the following good way of
> > > doing it?
> > >
> > > dd if=/dev/sda1 of=sda1.raw bs=64k
> >
> > Well, if the block device is missing from /dev then it won't work,
> > but otherwise, yes, that's a reasonable command. Your buffer is
> > quite small by today's standards. I'd be more inclined to do
> > something like:
> >
> > dd if=/dev/sd1 of=sda1.raw bs=1024k
> >
> > or even larger.
> >
> > Are you sure sda1 is missing from /dev?
> >
> > John
> >
>
> No I do have /dev/sda1, but I was used to using raw devices with dd,
> e.g. /dev/rwd0a on NetBSD or /dev/rdsk/* on Solaris. I wasn't sure if
> Linux deprecated raw device entries under /dev
>
>



--
Kind Regards
Oleg Buklanov