bug#25756: systemd mucking with partition tables ( was: bug#25756: Problems using "parted ... print" on nvme devices )

[Phil Susi]

On 2/16/2017 12:32 PM, Brian C. Lane wrote:
> I think the tricky part of that is going to be that when we open the
> device we don't really know what commands are going to be issued so it
> needs to be RDWR to allow for all the other possibilities.

I'm sure I have seen a patch floating around somewhere and been meaning
to merge it for some time that opens the device RO at first, then
switches to RW if and when it is required.  We should do that, but...

> There should be some way to lock out udev during your tests.

Why the hell has udev started mucking with the partition tables and dev
nodes every time someone opens the block device rw?  Parted and other
partitioning tools have always manipulated the in memory partition table
themselves after updating the disk, so why does systemd now think this
is its responsibility?

Parted takes care to only manipulate the individual partitions that have
changed, but I'm not sure that systemd doesn't just blow them all way
and recreate them all, causing significant system wide disruption.
There are some open bugs in Ubuntu for the unity desktop where drives
you have unlocked from your hotbar reappear due to them being "removed"
and reappearing due to this behavior.  systemd should stop this nonsense.