How to know if /dev/sdX is a connected USB or HDD?

Question

How can I know if /dev/sdX is a local HDD or usb key ? best doing this without root privileges.

OK , udevadm helped a lot:

For local HDD:

udevadm info --query=all --name=sdb | grep ID_BUS
E: ID_BUS=ata

For USB key:

udevadm info --query=all --name=sdc | grep ID_BUS
E: ID_BUS=usb

Answer 1

There are a few ways to tell without root privileges, many of them tricky/hacky:

Using /dev/disk/by-id:

find /dev/disk/by-id/ -lname '*sdX'

If this responds with something like /dev/disk/by-id/usb-blah-blah-blah, then it's a USB disk. Other prefixes include ata, dm, memstick, scsi, etc.

Using /dev/disk/by-path isn't significantly different:

find /dev/disk/by-path/ -lname '*sdX'

You'll get something like /dev/disk/by-path/pci-0000:00:1d.7-usb-0:1:1.0-scsi-0:0:0:0. This shows the device path leading to the disk. In this case, a rough path is PCI → USB → disk. (note the -usb-).

Using udev (I run Debian. My udevadm is in /sbin which isn't on my $PATH — yours might be elsewhere, on or off your $PATH):

/sbin/udevadm info --query=all --name=sdX | grep ID_BUS

You'll get the bus type the device is on. Remove the | grep ID_BUS for the complete listing of information (you may need to add |less).

If you have lshw installed, Huygens' answer may also work:

lshw -class disk -class storage | less

And look through the output for your disk. In less, try / sdX and look at the preceding, bus info lines — the first one will just say scsi@…, but the one several lines before it will be more enlightening. However, you really should run this as the superuser so it may not be suitable. (symptoms: on the laptop I tried it, it listed the SATA disk but not the USB one — running with sudo listed both)

There are other ones too, more or less direct than these ones.

Answer 2

I know a solution, but it requires 'root' privilege sadly. Anyway, you might still found it usefull:

sudo lshw -class disk -class storage

For each device it will print the logical name (e.g. /dev/sda) and bus info which in case of USB device would be something like 'usb@1:2'.

Sample output:

[...]
  *-storage
       description: SATA controller
       physical id: d
       bus info: pci@0000:00:0d.0
       configuration: driver=ahci latency=64
[...]
     *-disk:0
          description: ATA Disk
          physical id: 0
          bus info: scsi@2:0.0.0
          logical name: /dev/sda
[...]
  *-scsi
       physical id: 3
       bus info: usb@1:2
       configuration: driver=usb-storage
     *-disk
          description: SCSI Disk
          physical id: 0.0.0
          bus info: scsi@6:0.0.0
          logical name: /dev/sdc
[...]

Answer 3

This doesn't need root privileges:

There are a quick way to ask about a sdX:

grep -H . /sys/block/sda/{capability,uevent,removable,device,{model,type,vendor,uevent}}
/sys/block/sda/capability:52
/sys/block/sda/uevent:MAJOR=8
/sys/block/sda/uevent:MINOR=0
/sys/block/sda/uevent:DEVNAME=sda
/sys/block/sda/uevent:DEVTYPE=disk
/sys/block/sda/removable:0
/sys/block/sda/device/model:WDC WD360GD-00FN
/sys/block/sda/device/type:0
/sys/block/sda/device/vendor:ATA     
/sys/block/sda/device/uevent:DEVTYPE=scsi_device
/sys/block/sda/device/uevent:DRIVER=sd
/sys/block/sda/device/uevent:MODALIAS=scsi:t-0x00

The realy interesting file is capability, On my Debian, I have a genhd.h file, so:

eval $(sed -ne '
   s/#define.*GENHD_FL_\([A-Z0-9_]*\)[ \t]*\([0-9]*\) \?.*$/GENHD_FLAGS[\2]="\1"/p
  ' /usr/src/linux-headers-2.6.32-5-common-openvz/include/linux/genhd.h)
diskCapa=$(</sys/block/sda/capability)
for i in ${!GENHD_FLAGS[@]};do
    [ $((diskCapa & i)) -ne 0 ] && echo ${GENHD_FLAGS[i]}
  done
MEDIA_CHANGE_NOTIFY
UP
SUPPRESS_PARTITION_INFO

diskCapa=$(</sys/block/sdd/capability)
    for i in ${!GENHD_FLAGS[@]};do
    [ $((diskCapa & i)) -ne 0 ] && echo ${GENHD_FLAGS[i]}
  done
REMOVABLE
MEDIA_CHANGE_NOTIFY
UP
SUPPRESS_PARTITION_INFO

At all, for only knowing if flag removable is set, ask for /sys/block/sdX/removable is a lot simplier! ;-)

So an USB key is removable, but as there are lot of removable device, I would prefer to ensure that size of medium is greater than 0.

My script:

I have 3 HD and 3 usb keys:

for dev in $( 
    grep -Hv '^0$' /sys/block/*/removable |
        sed 's/removable:.*$/device\/uevent/' |
        xargs grep -H '^DRIVER=sd' |
        sed 's/device.uevent.*$/size/' |
        xargs grep -Hv '^0$' |
        cut -d / -f 4
  ) ;do
    echo "$dev \"$(
        sed -e 's/ *$//g' </sys/block/$dev/device/model
        )\""
  done

sdd "Storage Media"
sde "Freecom Databar"
sdf "silicon-power"

Nota: This is the very first part of a script I'm currently working on for installing a dual-boot live USB with ability of booting Debian or Ubuntu in persistent with a live-rw for Debian and a casper-rw for Ubuntu.

There is this very first part, which seem stable now and quiet, ( not as the rest of script with fdisk and mkfs).

#!/bin/bash

export USBKEYS=($(
    grep -Hv ^0$ /sys/block/*/removable |
    sed s/removable:.*$/device\\/uevent/ |
    xargs grep -H ^DRIVER=sd |
    sed s/device.uevent.*$/size/ |
    xargs grep -Hv ^0$ |
    cut -d / -f 4
))

export STICK
case ${#USBKEYS[@]} in
    0 )
    echo No USB Stick found
    exit 0
    ;;
    1 )
    STICK=$USBKEYS
    ;;
    * )
    STICK=$(
    bash -c "$(
        echo -n  dialog --menu \
            \"Choose wich USB stick have to be installed\" 22 76 17;
        for dev in ${USBKEYS[@]} ;do
            echo -n \ $dev \"$(
                sed -e s/\ *$//g </sys/block/$dev/device/model
                )\" ;
            done
        )" 2>&1 >/dev/tty
    )
    ;;
esac

[ "$STICK" ] || exit 0

echo $STICK...

Answer 4

I suggest just using hdparm or lshw (which you might need to install), and using sudo to execute it as root.

sudo hdparm -I /dev/sda
sudo lshw -short -C disk
sudo lshw -class disk -class storage

should all give you information.

Answer 5

After you plug in the USB device, run dmesg in a console window. You will be provided with some hints.

For example it will says something along the lines of "Device plugged in, mass storage /dev/sdd".