160

I want to mount a USB drive, two of them and I need two different mount points. Unfortunately, the Linux kernel underwent a name change and I can't figure out which /dev location is the right one. Is there a way to look through dmesg or /proc or somewhere else to find out which device node is a USB drive.

(I'm using ArchLinux if that helps any.../dev/sda is the first hard drive, /dev/sr0 is a dvd drive, etc.)

edit: The USB drive is connected to a USB hub. I looked through dmesg and it says the hub was connected and it scanned for the 3 devices connected to it. Still can't see where my USB drive is though.

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  • 1
    Can't see it? Maybe wait for a bit. Or try another USB port. See what differences there is in 'lsusb' – Nick Devereaux Mar 10 '09 at 23:02
  • Might want to rephrase the question somewhat - not all usb devices are disks, after all. – Arafangion Mar 10 '09 at 23:23
  • 3
    The df command shows you where it was mounted – Will Sheppard Aug 28 '13 at 14:09

13 Answers 13

83

Easiest way: Look at the output of dmesg after connecting the USB device. It should show you what /dev node was assigned to it.

  • 2
    dmesg works great, but I have a case where dmesg does not show the /dev node: [421963.864281] usb 3-6: new high-speed USB device number 32 using xhci_hcd What does this mean? How can I mount this device? The device shows up on lsusb... – modulitos Apr 25 '16 at 5:58
  • 1
    Actually, I figured it out. There was a kernel update since my last reboot that was causing this problem. After a reboot, my usb mounts just fine. Hopefully this helps someone! – modulitos Apr 25 '16 at 6:39
54

As long as you are running udev, you can do this easily by referencing /dev/disk/by-id/usb-manufacturername_serialnumber. These appear as symbolic links which you can either directly reference within your fstab, or which you can dereference using readlink -e to determine the associated block device.

Here's a real world example. On my machine, I have 3 USB hard drives connected. These each show up in /dev/disk/by-id with unique serial numbers (although they share a common manufacturer string). I have created symbolic links to each of these three unique entries, and can now quickly determine which drive is which (and which device is associated with each drive) by running readlink -e linkname. For example, running readlink -e /root/disk2 on my machine currently displays "/dev/sde", while readlink -e /root/disk3 produces no output whatsoever.

  • 15
    Short and simply: for devlink in /dev/disk/by-id/usb*; do readlink -f ${devlink}; done – Felipe Alcacibar Nov 25 '15 at 14:02
54

All of these are good suggestions, but the quickest and least verbose method is to just type the following in the terminal:

mount

which will give a list of all the mounted devices (this assumes the USB drive is mounted, which is usually the case with modern Linux distros).

  • 5
    No, it doesn't magically mount your device. You have to specify it with mount /dev/id /mount/point, so that doesn't work. – polym Jul 22 '14 at 14:02
  • 9
    My answer addresses the user's question 'Is there a way to look through dmesg or /proc or somewhere else to find out which device node is a USB drive.', and is not intended to provide guidance on the practicality of mounting a drive under Linux. – AnotherLongUsername Jul 23 '14 at 14:43
  • This answer solved an almost identical question for me. – Matthew Brown aka Lord Matt Oct 10 '14 at 11:04
  • 1
    I think automount behavior depends alot on the distro type. – jiggunjer Feb 2 '16 at 2:08
  • 1
    df too, i suppose. – Alexey May 26 '16 at 16:11
24

Try the command udevinfo -q all -n /dev/sda, where /dev/sda is the path to your disk. This gives you a boatload of info about the disk you're looking at - there's an entry that tells you about the bus it's connected to.

This of course saves you from having to grep through dmesg and/or logs.

Update

udevadm info --query=all -n /dev/sda 

From at least Jul 2010 [1] udevinfo was substituted in Debian (and derived) by udevadm info with a little transient with which there were symlinks soon deprecated and removed (you can still found them in old not updated machine). Always from [1] we can read:

In udev 117, udevadm was introduced and udevinfo and other programs turned into compatibility symlinks. The symlinks were deprecated in udev 128 and removed for good in udev 147.

  • 8
    In Debian, udevinfo is renamed udevadm. – Steve Pomeroy Aug 23 '11 at 14:44
  • 8
    On Ubuntu, the command seems to be "udevadm info --query=all -n /dev/sda" – machineghost Dec 13 '11 at 6:06
  • I suppose they renamed the command at some point - when I wrote the answer (ages ago) the command worked on the ubuntu system that I posted it from ;) – Eltariel Dec 15 '11 at 5:08
  • Command works still in ubuntu, udevadm info --query=all -n /dev/ttyUSB1 – Siddharth Jun 4 '13 at 8:43
  • 1
    udevadm info --query=all -n /dev/ttyUSB in Fedora too. – slm Oct 26 '13 at 14:50
22

the simplest method to see what's going on is just typing (as root of course):

blkid -c /dev/null

this gives you a complete overview about all block devices even if not mounted

  • Not all distro have this. Which were you using? – New Alexandria Sep 19 '15 at 17:26
  • This outputs nothing on my Raspbian distro. – IgorGanapolsky Aug 8 '16 at 6:17
  • Command not found: blkid – IgorGanapolsky Sep 28 '16 at 17:13
  • No output from this command on Ubuntu 14.04 64-bit. – gbmhunter Apr 17 '17 at 18:15
11

/dev/disk/by-* is the easiest way in this case, if for some reason you want to make life more interesting you can use HAL.

To list all devices you use:

hal-device

To get a specific property you use (this will return /dev/sd* on a USB storage device):

hal-get-property --udi $UDI --key block.device

There is also:

hal-find-by-capability
hal-find-by-property

If you want to make it even more complicated you can relatively easy write yourself a HAL based auto mounter, which can be quite handy if you want to automate things completly.

And just for completeness there are also:

lsusb -v
lshw

Which provides some general information about USB and your hardware in general.

  • 2
    /dev/disk/by-id/*usb* is very helpful. – Rob Dec 12 '11 at 18:56
  • /dev/disk/by-label ftw. Thanks :) – Triptych Jun 17 '13 at 13:25
10
sudo fdisk -l

And just analyse the result.

  • 1
    fdisk man page "If no devices are given, those mentioned in /proc/partitions (if that exists) are used." Running fdisk may not be an option... Based on one Debian system that I know doesn't have it installed, my guess is that some GPT systems might not install the unneeded software. Still, checking /proc/partitions ought to be an option. – TOOGAM Nov 10 '15 at 7:33
  • This was the only option that worked fine for me. I am sorry if it didn't work for you! – Felipe Nov 10 '15 at 21:52
8

Use

ls -l /dev/disk/by-id/usb*

Under the default udev rules, that will show you most usb devices and it will show you the symlink to their block-device name on the system.

If that doesn't work, look at /dev/disk/by-id/ directly.

6

For USB devices you can simply do

REMOVABLE_DRIVES=""
for _device in /sys/block/*/device; do
    if echo $(readlink -f "$_device")|egrep -q "usb"; then
        _disk=$(echo "$_device" | cut -f4 -d/)
        REMOVABLE_DRIVES="$REMOVABLE_DRIVES $_disk"
    fi
done
echo Removable drives found: "$REMOVABLE_DRIVES"
  • 1
    +1. Simple and concise script to do the task automatically. – leesei Nov 18 '15 at 14:28
2

Take a look at the tree under /dev/disk. It lists disks and their partitions (file systems) by various schemes.

2

/var/log/message if dmesg no longer has the information.

0

If you unplug the USB drive and plug it back in, you should see it initialize from the kernel (dmesg)

0

Based on the excellent answer from stormlash and with a dependency on udev to populate the "/dev/disk/by-id/usb" device tree, you could define a predicate (Bash) as follows:

is_usb_device() {
    local device_path=$1        # such as /dev/sdc
    for devlink in /dev/disk/by-id/usb*; do
        if [ "$(readlink -f "$devlink")" = "$device_path" ]; then
            return 0
        fi
    done
    return 1
}

And then use it:

if is_usb_device "/dev/sdg"; then
    echo "/dev/sdg is a usb device"
else
    echo "/dev/sdg is not a usb device"
fi

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