Re: Inhibiting device startup at boot

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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



[Index of Archives]     [Older Fedora Users]     [Fedora Announce]     [Fedora Package Announce]     [EPEL Announce]     [EPEL Devel]     [Fedora Magazine]     [Fedora Summer Coding]     [Fedora Laptop]     [Fedora Cloud]     [Fedora Advisory Board]     [Fedora Education]     [Fedora Security]     [Fedora Scitech]     [Fedora Robotics]     [Fedora Infrastructure]     [Fedora Websites]     [Anaconda Devel]     [Fedora Devel Java]     [Fedora Desktop]     [Fedora Fonts]     [Fedora Marketing]     [Fedora Management Tools]     [Fedora Mentors]     [Fedora Package Review]     [Fedora R Devel]     [Fedora PHP Devel]     [Kickstart]     [Fedora Music]     [Fedora Packaging]     [Fedora SELinux]     [Fedora Legal]     [Fedora Kernel]     [Fedora OCaml]     [Coolkey]     [Virtualization Tools]     [ET Management Tools]     [Yum Users]     [Yosemite News]     [Gnome Users]     [KDE Users]     [Fedora Art]     [Fedora Docs]     [Fedora Sparc]     [Libvirt Users]     [Fedora ARM]

  Powered by Linux