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Occasionally on Lubuntu 12.04 64bit, when I plug in my iPod touch or my Sansa ClipZip+, my USB wifi dongle will stop working, and the device will not be mounted. The only way I can fix this is by restarting it. This doesn't happen every time I plug in one of the two, but it can get very annoying.

What can I do to find out why this is happening? Are there logs I can look at to see why lubuntu's USB stops working? Is there a way to restart usb so I don't have to restart my entire computer?

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up vote 1 down vote accepted

To watch the logs as something is connected you can either monitor kern.log in gnome-system-monitor or other logging software, or use the command-line and enter

tail -f /var/log/kern.log

When your device is connected you will see a lot of information, such as

usb 1-3: new high-speed USB device number 5 using ehci_hcd
Initializing USB Mass Storage driver...
scsi2 : usb-storage 1-3:1.0
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
usbcore: registered new interface driver uas
scsi 2:0:0:0: Direct-Access     CREATIVE ZEN_Stone

You can keep the log open in the terminal and monitor when any errors occur as well. You can grep the log for past errors with grep -i usb /var/log/kern.log, but you will probably need to use some more specific search terms with grep such as error or the name of your hardware, as just using usb as a search term will return a lot of results.

Most of the advice you read to restart the USB subsystem won't work in Ubuntu, and this way here at Ubuntu forums doesn't seem to work for me, but you could try restarting udev by entering

sudo service udev restart

but you may very well still have to reboot.

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