Re: [ovirt-users] [OT] Major and minor numbers assigned to /dev/vdx virtio devices
On Tue, Jul 14, 2020 at 4:40 PM Stefan Hajnoczi wrote:
> On Mon, Jul 13, 2020 at 09:53:31PM +0300, Nir Soffer wrote:
> > On Wed, Jul 1, 2020 at 5:55 PM Gianluca Cecchi
> > wrote:
> > >
> > > Hello,
> > > isn't there an official major/minor numbering scheme for virtio disks?
> > > Sometimes I see 251 major or 252 or so... what is the udev assignment
> logic?
> > > Reading here:
> > > https://www.kernel.org/doc/Documentation/admin-guide/devices.txt
> > >
> > > 240-254 block LOCAL/EXPERIMENTAL USE
> > > Allocated for local/experimental use. For devices not
> > > assigned official numbers, these ranges should be
> > > used in order to avoid conflicting with future assignments.
> > >
> > > it seems they are in the range of experimental ones, while for example
> Xen /dev/xvdx devices have their own static assignment (202 major)
>
> No, the Linux virtio_blk driver does not use a static device major number.
>
> Regarding udev, on my Fedora system
> /usr/lib/udev/rules.d/60-persistent-storage.rules has rules like this:
>
> KERNEL=="vd*[!0-9]", ATTRS{serial}=="?*", ENV{ID_SERIAL}="$attr{serial}",
> SYMLINK+="disk/by-id/virtio-$env{ID_SERIAL}"
>
> The rules match on the "vd*" name. If you are writing udev rules you
> could use the same approach.
>
> Is there a specific problem faced when there is no static device major
> number?
>
> Stefan
>
Thanks for the information.
No, it was only a curiosity: during a recovery action (actually it was a
"poor man" P2V operation using dd) where I had to rebuild initrd file and
to reinstall grub in a chroot environment,
I had to run mknod commands to manually create the /dev/vdax files and
comparing two different existing guests I stumbled upon their /dev/vda
files that had different major/minor numbers, so I was not sure what to
use
Gianluca
Re: [ovirt-users] [OT] Major and minor numbers assigned to /dev/vdx virtio devices
On Mon, Jul 13, 2020 at 09:53:31PM +0300, Nir Soffer wrote:
> On Wed, Jul 1, 2020 at 5:55 PM Gianluca Cecchi
> wrote:
> >
> > Hello,
> > isn't there an official major/minor numbering scheme for virtio disks?
> > Sometimes I see 251 major or 252 or so... what is the udev assignment logic?
> > Reading here:
> > https://www.kernel.org/doc/Documentation/admin-guide/devices.txt
> >
> > 240-254 block LOCAL/EXPERIMENTAL USE
> > Allocated for local/experimental use. For devices not
> > assigned official numbers, these ranges should be
> > used in order to avoid conflicting with future assignments.
> >
> > it seems they are in the range of experimental ones, while for example Xen
> > /dev/xvdx devices have their own static assignment (202 major)
No, the Linux virtio_blk driver does not use a static device major number.
Regarding udev, on my Fedora system
/usr/lib/udev/rules.d/60-persistent-storage.rules has rules like this:
KERNEL=="vd*[!0-9]", ATTRS{serial}=="?*", ENV{ID_SERIAL}="$attr{serial}",
SYMLINK+="disk/by-id/virtio-$env{ID_SERIAL}"
The rules match on the "vd*" name. If you are writing udev rules you
could use the same approach.
Is there a specific problem faced when there is no static device major
number?
Stefan
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Re: [ovirt-users] [OT] Major and minor numbers assigned to /dev/vdx virtio devices
On Wed, Jul 1, 2020 at 5:55 PM Gianluca Cecchi wrote: > > Hello, > isn't there an official major/minor numbering scheme for virtio disks? > Sometimes I see 251 major or 252 or so... what is the udev assignment logic? > Reading here: > https://www.kernel.org/doc/Documentation/admin-guide/devices.txt > > 240-254 block LOCAL/EXPERIMENTAL USE > Allocated for local/experimental use. For devices not > assigned official numbers, these ranges should be > used in order to avoid conflicting with future assignments. > > it seems they are in the range of experimental ones, while for example Xen > /dev/xvdx devices have their own static assignment (202 major) This question belongs to qemu-discuss. Also added some people that may help. Nir
