On Tue, 2020-12-01 at 13:33 -0700, Chris Murphy wrote: > On Tue, Dec 1, 2020 at 1:07 PM Samuel Sieb <samuel@xxxxxxxx> wrote: > > > > On 12/1/20 8:42 AM, Patrick O'Callaghan wrote: > > > On Tue, 2020-12-01 at 09:01 -0700, Chris Murphy wrote: > > > > On Tue, Dec 1, 2020 at 6:59 AM Tom Horsley <horsley1953@xxxxxxxxx> wrote: > > > > > > > > > > On Tue, 1 Dec 2020 14:52:21 +0100 > > > > > Roberto Ragusa wrote: > > > > > > > > > > > How do you power them down? > > > > > > > > > > I don't know about the original poster, but my "noauto" disks > > > > > timeout and power down all by themselves, then even when they aren't > > > > > mounted at all, every time I reboot, the reboot hangs while it > > > > > spins up the disks for some reason. I constantly wish I could make > > > > > it stop doing that. > > > > > > > > Enumeration. I'm not sure if it's udev scanning everything, or the > > > > kernel or both. And also maybe libblkid, to know what everything is. > > > > The only way it can know what it is, it needs to be spun up to read > > > > the partition map and all the signatures on each partition. > > > > > > Obviously it needs to spin up if it needs to know these things. My > > > point is that it doesn't need to know them until I tell it. > > > > But it can't know that it shouldn't until it knows what's there. :-) > > The kernel scanning the USB bus will trigger the dock to check the > > drives which will spin them up. Even if the dock didn't, the kernel > > would still check the drives, so they would still be started. > > Yep. For sure the kernel is what's responsible for reading the > partition table. And that alone would cause a spin up. e.g. > > [ 6.426044] sdb: sdb1 sdb2 > > Only later does udev come in with "aha! a partition! let's scan it!" > and then I see things like: > > [ 6.506645] BTRFS: device label fedoraroot devid 2 transid 398800 > /dev/sdb2 scanned by systemd-udevd (326) > > And there is an interaction with libblkid in the kernel to determine > that this partition contains a Btrfs signature, what the label is, > what the fs UUID is. And it's udev along with that information from > libblkid that creates the disk by label, disk by uuid, disk by > partuuid, disk by whatever. Just for the record, these drives are using ext4, not BTRFS, though that may change. > The parameter to use to get detailed udev reporting dumped into the > journal is udev.log_priority=debug and then you can see what does > what, and in what order. Thanks. poc _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx
