On Thu, Oct 12, 2017 at 6:42 PM, Mike Larkin <mlar...@azathoth.net> wrote:
>> oh. I didn't know that is how it was finding things.
>>
>
> When booting it this way in qemu, qemu just reports the ID as "".
>
> So are you sure this is the way it is supposed to work?
Yes... with some caveats.
The Linux device manager (udev, I think? They've gone through
several.) creates symlinks under /dev/disk/by-{id,label,path,uuid}/,
so that you can use more permanent names in case the disk order (sda,
sdb, etc.) changes; there are also library calls to open a
device/partition by ID, UUID, etc., (via libblkid I believe, which
lets you use things like LABEL=foo or UUID=abcd... as the block device
passed to mount(8) or listed in fstab). The SUSE installer is
"helpfully" attempting to use these IDs; e.g. with a SATA disk under
VirtualBox, it uses a repo URL of
'hd:///?device=/dev/disk/by-id/ata-VBOX_HARDDISK_VB40007e3d-cdaea0a1-part2'.
However, you are correct that qemu virtio disks do not report IDs (or
report blank ones) -- at least by default (apparently with recent
qemu, there is an option to set a drive's serial number, but it
doesn't seem to be commonly used). I did a test installation of
openSUSE under Proxmox VE (qemu/KVM) using virtio disks, and the only
thing under /dev/disk/by-id is the emaulated IDE CD-ROM. -- nothing
for /dev/vda or vdb. Notably, the installer configured its repo as
'hd:///?device=/dev/vda2' without me having to tell it that, as I had
to under vmm.
By comparison, the opensuse VM I installed under OpenBSD vmm *does*
show some 'by-id' devices:
/dev/disk/by-id:
total 0
lrwxrwxrwx 1 root root 9 Oct 13 13:21 virtio-______L____I_U_ -> ../../vdb
lrwxrwxrwx 1 root root 10 Oct 13 13:21 virtio-______L____I_U_-part1 ->
../../vdb1
lrwxrwxrwx 1 root root 10 Oct 13 13:21 virtio-______L____I_U_-part2 ->
../../vdb2
(Currently /dev/vda is the VM's hard disk and vdb is the ISO...
strange that there are only links for vdb, but not vda. Of course
accessing via these symlinks works, since they point at the real
device, but doing whatever library call to open
'virtio-______L____I_U_-part2' would most likely fail, and obviously
the correct symlinks did not exist during installation.)
My best guess is that when udev gets a blank ID, it skips the by-id
stuff, and thus the installer uses the real disk device, but since vmm
doesn't implement that call, instead of marking the disk as not having
an ID, invalid disk IDs somehow get used.
-Andrew
