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#1 2013-12-07 11:54:27
- CrazyTux
- Member
- Registered: 2013-08-23
- Posts: 32
USB disk not recognized
I just plugged in my external usb3 disk, and nothing appeared in /dev. I tried plugging it into a usb2 port, still nothing. When I did the same on an Ubuntu box, it worked. Also, it is listed in lsusb. Just not in /dev, so I can't mount it. Why is this? Is there any way to make it appear?
PS: I'm rather new to Arch, so I don't know that much.
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#2 2013-12-07 11:56:46
- karol
- Archivist
- Registered: 2009-05-06
- Posts: 25,440
Re: USB disk not recognized
Reboot and try again.
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#3 2013-12-07 12:04:08
- CrazyTux
- Member
- Registered: 2013-08-23
- Posts: 32
Re: USB disk not recognized
That did it! Why? Is it a common problem?
So embarrassed that I didn't try rebooting 
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#4 2013-12-07 12:05:05
- Grant
- Member
- From: Italy
- Registered: 2012-12-15
- Posts: 246
Re: USB disk not recognized
That usually happens when you've just upgraded the kernel.
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#5 2013-12-07 19:18:42
- ewaller
- Administrator
- From: Pasadena, CA
- Registered: 2009-07-13
- Posts: 20,690
Re: USB disk not recognized
That did it! Why? Is it a common problem?
So embarrassed that I didn't try rebooting
To expand on Grant's comment. It really is not a problem; at least it is not a systemic problem. As Arch is designed to run on a wide variety of hardware, we cannot build a custom kernel that contains all the drivers for a given computer. What is more, it is impractical to build in every module for every USB device that may be encountered by a given computer. As such, Arch, like most distributions, use dynamically loaded kernel modules. Those modules have a one to one correspondence with a given kernel. When you update a kernel in a running system, the modules for the new kernel replace the modules for the old kernel in /lib. In the mean time, the old kernel is the one that is remains running until the next reboot.
After you replaced your kernel modules, but did not reboot, you inserted a USB device. The kernel probably noticed; you can tell by looking at the output of dmesg. The kernel then would have tried to find its modules, but they are gone, having been replaced with the modules for a different kernel.
Rebooting pulls in the new kernel which is able to use the new modules.
So the 'problem' exists between the keyboard and chair (PEBKAC) 
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
The shortest way to ruin a country is to give power to demagogues.— Dionysius of Halicarnassus
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