From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrey Borzenkov <arvidjaar@mail.ru>
Date: Sat, 21 Apr 2007 10:29:36 +0000
Subject: Re: [PATCH] creating link /dev/root to device / is mounted from
Message-Id: <200704211429.40740.arvidjaar@mail.ru>
MIME-Version: 1
Content-Type: multipart/mixed; boundary="===============1774747757=="
List-Id: <linux-hotplug.vger.kernel.org>
References: <200704201246.21524.zzam@gentoo.org>
In-Reply-To: <200704201246.21524.zzam@gentoo.org>
To: linux-hotplug@vger.kernel.org

--===============1774747757==
Content-Type: multipart/signed; boundary="nextPart5210464.XSf00eGj6F";
	protocol="application/pgp-signature"; micalg=pgp-sha1
Content-Transfer-Encoding: 7bit

--nextPart5210464.XSf00eGj6F
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

On Saturday 21 April 2007, Matthias Schwarzott wrote:
> On Freitag, 20. April 2007, Kay Sievers wrote:
> > On 4/20/07, Matthias Schwarzott <zzam@gentoo.org> wrote:
> > > Some software (like hal) needs the /dev/root link (as /proc/mounts can
> > > contain it).
> >
> > Right, but HAL doesn't need it, it just assumes that device-file
> > entries in /proc/mounts are also available in /dev.
> >
> > The "/dev/root missing but in /proc/mounts" only happens for people
> > who run their own compiled kernels without an initramfs.
> >
> > > The attached patch contains one program which compares the major/minor
> > > number supplied to it on the command-line with the numbers of the
> > > device / is located on.
> > > It is used with this rule (see 60-root_link.rules):
> > > SUBSYSTEM=3D=3D"block", PROGRAM=3D=3D"blockdev_is_root $major $minor",
> > > SYMLINK+=3D"root"
> >
> > Why do we want to run a program for _every_ block device, just to
> > create /dev/root? It's an operation you only need to do once at
> > bootup, and the root-device is obviously already there, before you
> > start udev out of the rootfs. :)
>
> I think this is not too bad, as the program itself is only around 3k size.
>
> > The udev init-script checks if /dev is already mounted with tmpfs from
> > initramfs, if not, it will need to do it, and at that point, we can
> > just mknod /dev/root, can't we?
>
> Well, our initramfs does not move its /dev to new mounted root filesystem,
> but we get a completely fresh tmpfs.
>

I believe, most iplementations do. Actually how you solve the issue=20
with /dev/null & Co. without it?

> We also can just have a program to write out major/minor of "/" and then
> mknod it (outside of udev)
> But I really like a link better.
> Here I also can search udev-database (or whatever)
>

Yes that is nice. What about a simple program that can manupulate udev=20
database? I am not sure if the format allows it though.

=2Dandrey

> For example when /usr is already mounted (for udevinfo):
> dev_nr=3D$(root_get_dev_nr)
> dev_path=3D$(udevtrigger --verbose --attr-match=3Ddev=3D${dev_nr})
> dev_name=3D$(udevinfo -q name --path ${dev_path})
> ln -s /dev/${dev_name} /dev/root
>
>
> Or inject some rule into udev like
> ATTR{dev}=3D=3D"${dev_nr}", SYMLINK+=3D"root"
> But how to inject? /etc is read-only at udevd starting. Or can rule-files
> include other rule files? Like in /dev/.udev/
>
> Matthias



--nextPart5210464.XSf00eGj6F
Content-Type: application/pgp-signature

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (GNU/Linux)

iD8DBQBGKeeRR6LMutpd94wRAryqAKC9jOXPOU2OPw8PTVjC6Tnjg4qB/ACaA8aG
4JhOcxHMOaPxcTfWebm3amQ=
=sQiV
-----END PGP SIGNATURE-----

--nextPart5210464.XSf00eGj6F--


--===============1774747757==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

-------------------------------------------------------------------------
This SF.net email is sponsored by DB2 Express
Download DB2 Express C - the FREE version of DB2 express and take
control of your XML. No limits. Just data. Click to get it now.
http://sourceforge.net/powerbar/db2/
--===============1774747757==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel

--===============1774747757==--