Re: External USB HD showing up late in /dev
Davide Mancusi wrote:
> Hi .*,
>
> I have an external USB hard disk that I use for automated
> backups. I have written the following udev rules:
> SUBSYSTEMS=="usb", ATTRS{serial}=="574341535530323537353839",
> KERNEL=="sd?", SYMLINK+="exthd", GROUP="plugdev" SUBSYSTEMS=="usb",
> ATTRS{serial}=="574341535530323537353839", KERNEL=="sd?1",
> SYMLINK+="exthd1", GROUP="plugdev"
> to create symlinks to the right device and partition, and I have a
> fstab entry:
> /dev/exthd1 /mnt/exthd ext3 user,auto,errors=remount-ro 0 2
> to mount the backup partition automatically at boot time.
>
> The problem is that sometimes, when init calls
> fsck, /dev/exthd1 has not appeared yet, fsck bombs and init drops me to
> an emergency shell. This happens about 50% of the times. Then I use the
> emergency prompt to check if /dev/exthd1 actually exists, and, again,
> 50% of the times it doesn't; the /dev/sd?1 file is always there,
> though. When /dev/exthd1 doesn't exist, a "udevadm trigger" will bring
> it up.
>
> This looks like some kind of race condition between kernel and
> udev, but I don't really understand why udev doesn't pick on the new
> devices automatically, as soon as the kernel creates them. I have tried
> to add WAIT_FOR="/dev/exthd1" to my udev rule, but it didn't help.
>
> Any help would be appreciated.
>
> Davide
>
Upto 2.6.26 I know there is a delay_use option for usb_storage.
It's set to 5sec by default. I didn't look for such an option in 2.6.28, but
as delay_use is doing nothing I assume it was either removed or replaced.
What you describe sounds like this default is working for you.
Are you using 2.6.26 or similar.
try adding following somehwere in your /etc/modprobe.d/ files
options usb-storage delay_use=0
regards
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