USB device probing is inconsistent
 

I think this problem is caused by udev, but maybe also the kernel.

I just bought 3 new USB backup drives, WD My Passport brand, 2TB each. I have Slackware64-current installed from the packages as of 2013-08-21. When I boot up the system installed on the /dev/sda hard drive on SATA (there is also /dev/sdb on SATA), with one new USB drive plugged in, the USB drive does not come up in /proc/partitions, not even the whole drive line. If I unplug the drive, then plug it back in, then it does show up as /dev/sdc.

But this is MOST of the time. ONE time it did show up in the initial boot, as /dev/sdh. But even then replugging it changed it to /dev/sdc.

When I boot the install DVD, it always shows up in that system as dev/sdh.

But in the cases where it does not show up in /proc/partitions, it does show up in the output of "lsusb -t" as a storage device.

And udev is always reporting errors on devices up through /dev/sdg. Is it just a bad udev configuration? udev seems to always be a big trouble maker, and it has one of the most difficult configuration schemes I have ever seen (requires knowledge about existing devices when the goal should be to operate correctly regardless of the devices).

I'm actually wanting to install Slackware on the USB drive as a backup system. I probably could install it. But apparently when I boot it, it won't see its root filesystem device and won't be able to run.

I'd append a "rootdelay=20" or so in /etc/lilo.conf and identify the device by its UUID (plug it in then run blkid as root to know which it is), in /etc/fstab as in /etc/lilo.conf.

I'm not using lilo. I'm guessing you mean to have the kernel wait before trying to mount root. But keep in mind that the kernel never sees the USB device. It's not a matter of time.

You could always try to remove udev and replace it with mdev and hotplug. Few guys had a similar setup working with Gentoo a while back.

It will eliminate auto-mounting drives, meaning you'll have to setup optical drives manually and mount stuff by hand, but it works fairly well if udev is being a total pain and needs to be sacrificed and put to death.

Hotplug's last Slackware source and binary package should work with modern systems, though you may want to pour over the legacy scripts to make sure they're up-to-date. Hotplug should be able to work where mdev doesn't with auto-detecting devices and loading the driver modules for them.

Binary package:

http://mirrors.slackware.com/slackwa...-noarch-11.tgz

Source (and SlackBuild):

http://mirrors.slackware.com/slackwa...rce/a/hotplug/

Information on mdev can be found here:

https://wiki.gentoo.org/wiki/Mdev

Be warned, this is a rather advanced method to solving udev issues, and shouldn't be attempted unless udev absolutely has to be gotten rid of.

There is also Hotplug2 you can look into as well:

http://code.google.com/p/hotplug2/