How to reconnect a logically disconnected USB device?

Question

It is possible for a USB storage device to become logically disconnected: the device is still plugged in, but is invisible from the operating system (e.g. it's not listed under /proc/bus/usb). Maybe this can happen to other kinds of USB or other removable devices as well. This can happen for example:

after Nautilus has unmounted a USB storage device;
after VirtualBox has claimed a USB storage device (the device disappears from the Linux host when it is attached in the guest, and does not automatically reappear if it is detached from the guest).

What is going on in the driver or in the hardware, and most importantly, (how) can the device be logically reconnected (without physically plugging it out and back in)?

Note that this question is not about mounting. In the “logically disconnected” state, the kernel believes there is nothing on the USB bus (and so of course there is no entry under /dev).

Shameless plug: answer working for kernel 3.x and up – Dmitry Grigoryev Jan 19 '16 at 20:36 — Dmitry Grigoryev, Jan 19 '16 at 20:36

jon_d · Answer 1 · 2011-02-15T17:07:10.287

21

It is sometimes possible to do a power cycle on branch of the USB bus where the device is plugged :

# echo suspend > /sys/bus/usb/devices/1-1/power/level
# echo auto > /sys/bus/usb/devices/1-1/power/level

The 1-1 should be adjusted to your configuration. You can see to which part of the USB tree your device is plugged by running lsusb -t before ejecting it.

You can find detailed information on the linux-usb mailing-list, this thread for example.

edited Feb 15 '11 at 17:07

answered Feb 15 '11 at 16:45

jon_d

1,043

7

"suspend" doesn't work on kernels after 2.6.36. – alexisdm Jan 31 '14 at 13:14
1

Assuming dmesg reports the correct device ID ("usb 9-4: USB disconnect [...]"), this does not work on latest Arch Linux. There is no path /sys/bus/usb/devices/9-4 afterwards. – l0b0 Mar 21 '14 at 07:07
1
dmesg:

WARNING! power/level is deprecated; use power/control instead

http://superuser.com/questions/371068/is-there-a-way-to-power-down-a-usb-device-using-software

socketpair

Dec 21 '15 at 18:06

Also suspend is no longer supported on recent kernel versions.... – Gert van den Berg Jun 22 '18 at 14:39

permission denied even with sudo – endolith Feb 01 '22 at 17:23

score 12 · Answer 2 · edited Aug 29 '16 at 07:09

12

udevadm info -a -n /dev/sdb

Now check for Kernel. E.g. if it is connected to Port 2 of Front UIP then it would be 1-1.2 and if it is connected to Port 1 of Front UIP then it would be 1-1.1.

For Port 2 : To disconnect USB :

echo '1-1.2' | tee /sys/bus/usb/drivers/usb/unbind

To connect USB :

echo '1-1.2' | tee /sys/bus/usb/drivers/usb/bind

edited Aug 29 '16 at 07:09

Gilles 'SO- stop being evil'

829,060

answered Aug 29 '16 at 04:07

Udaya

171

Works on a 3.10 kernel for me where the suspend/auto didn't. – Paul Aug 26 '22 at 20:47

score 6 · Answer 3 · answered Apr 01 '11 at 17:46

Reset the device, or the hub it is connected to, and the device should reappear. Here is a small program to do that:

http://marc.info/?l=linux-usb-users&m=116827193506484

It works for most USB drives I've tried, but there are exceptions, like my Kingston DT 101 II 4GB, which fails INQUIRY and READ CAPACITY commands after reset, and remains unusable until power-cycled.

You can power-cycle the device without unplugging if it gets power from the port, and your USB hub supports per-port power control. Here is a small program to control the power:

http://marc.info/?l=linux-usb-devel&m=113724451205634

Unfortunately, almost no USB hubs support this feature, and it's very difficult to find one that supports it. Manufacturers do not advertise it. Many hubs also lie about it, for example if you do "lsusb -v" you can see "Per-port power switching" advertised in "wHubCharacteristic", but in reality it does not work. The chipset may support it, but it was easier/cheaper for the manufacturer to connect port power pins directly to the power supply instead of going through the chipset.

score 5 · Answer 4 · edited May 11 '22 at 12:04

5

The following will disconnect the USB device.

sudo eject /dev/sde

The following will reconnect the USB device.

sudo eject -t /dev/sde

The above works on my Linux Mint.

edited May 11 '22 at 12:04

SouthwindCG

103

answered Jul 07 '19 at 05:07

Matthew Wai

437

score 5 · Answer 5 · edited Apr 13 '17 at 12:22

5

I found this answer to work great on my Gentoo system. Please also remember to re-enable your device if it's an important piece of your system (e.g. mouse or keyboard).

sudo sh -c 'AUTHFILE="/sys/bus/usb/devices/5-2/authorized" ; echo 0 > "$AUTHFILE" ; sleep 1 ; echo 1 > "$AUTHFILE"'

To see what you're disabling/re-enabling:

cat /sys/bus/usb/devices/5-2/product

edited Apr 13 '17 at 12:22

Community

1

answered Apr 28 '13 at 08:54

Avio

909

This seemed to do the trick on my modern Fedora 25 system. Some of the other methods are no longer possible. – xenithorb Dec 23 '16 at 08:28
no product file in those paths with kernel 6.1.63 -- answer outdated? – Robert Siemer Jan 25 '24 at 11:29

score 4 · Answer 6 · edited Apr 13 '17 at 12:22

4

I have tried most of the above suggestions, but they didn't work for me. I found how to reset a USB device from the command line: https://askubuntu.com/a/290519

echo $i >/sys/bus/pci/drivers/ehci_hcd/bind

where $i you can use appropriate device ID from /sys/bus/pci/drivers/ehci_hcd.

edited Apr 13 '17 at 12:22

Community

1

answered Feb 21 '14 at 22:15

Kakanakov

41

score 4 · Answer 7 · edited Sep 25 '20 at 08:50

4

This script disconnects and reconnects all USB devices.

#!/bin/bash
for i in /sys/bus/pci/drivers/[uoex]hci_hcd/:; do
  [ -e "$i" ] || continue
  echo "${i##/}" > "${i%/}/unbind"
  echo "${i##/}" > "${i%/}/bind"
done

edited Sep 25 '20 at 08:50

Gilles 'SO- stop being evil'

829,060

answered Sep 25 '20 at 08:23

oat

62

1

Welcome to the site, and thank you for your contribution. In order to be helpful to as wide an audiance as possible, would you mind editing your post to include some explanation on how your solution achieves its goal? – AdminBee Sep 25 '20 at 08:46
3

@AdminBee Added. Technically it does answer the question, but it reconnects all USB devices, which could be a problem. – Gilles 'SO- stop being evil' Sep 25 '20 at 08:51
No problem. To do for just one device get the address or name from "sudo lsusb" and run /usr/bin/usbreset for it. In my case /usr/bin/usbreset 'USB3.1 Hub' – oat Sep 25 '20 at 16:03

score -2 · Answer 8 · answered Jun 16 '21 at 20:56

-2

Many of these things don't work for me, either due to absence of data or my failure to comprehend. I simply suspended my machine and then resumed. My USB mounted mouse was restored.

answered Jun 16 '21 at 20:56

Cornell

1

You are making a comment on a 10 year old question, but your comment is basically "I suspended and resumed and it worked"? That is NOT a solution. – number9 Jun 17 '21 at 13:10

score -5 · Answer 9 · answered Feb 16 '11 at 05:42

-5

I'm uncertain that I'm properly understanding your question, but on my system if a usb device is plugged in but not mounted I can 'see it' by

$> fdisk -l

That tells me what device it's associated with (i.e. /dev/sdd1 or something), then I manually mount it.

answered Feb 16 '11 at 05:42

bev

643
4
8
17

5

Again: no, the question is not about a filesystem becoming inaccessible (i.e. unmounted), it's about a device becoming inaccesible (the kernel doesn't see a device, so of course there is no entry under /dev). – Gilles 'SO- stop being evil' Feb 16 '11 at 08:22

How to reconnect a logically disconnected USB device?

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