USB detected but not found in /dev

I have a Parabola (arch)/Linux installation with Kernel 4.9.6. When I insert a usb external hard disk I can see it in lsusb as

Bus 002 Device 055: ID 0411:01de BUFFALO INC. (formerly MelCo., Inc.) External Hard Drive HD-PCTU3 [Buffalo MiniStation]

However I cannot find it as a block device anywhere in /dev. For instance, lsblk returns

NAME              MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                 8:0    0 223.6G  0 disk 
└─sda1              8:1    0 223.6G  0 part 
  └─root          254:0    0 223.6G  0 crypt
    ├─matrix-swap 254:1    0     2G  0 lvm   [SWAP]
    ├─matrix-root 254:2    0 199.4G  0 lvm   /
    ├─matrix-boot 254:3    0     2G  0 lvm   /boot
    └─matrix-var  254:4    0  20.2G  0 lvm   /var

Here sda is my hard disk with some lvm partitions. The usb device doesn't show up in /dev/disk/by-id either. A check at dmesg yields

usb 2-1: new high-speed USB device number 55 using ehci-pci

and nothing else. I can't figure out what is the problem. Could anyone help me out?

Solution 1:

The most common cause:

You have upgraded the kernel recently, but haven't yet rebooted into it. When you connect a new device, udev tries to load modules matching the running kernel – but you don't have them anymore! Instead your /lib/modules only has files for the installed newer kernel.

Check whether uname -r and pacman -Q linux show different versions; if so, reboot.