A common problem when using adb to access your Android phone via USB is:

$ adb devices List of devices attached ????????????    no permissions 

According to official Android Developers website:

If you’re developing on Ubuntu Linux, you need to add a rules file that contains a USB configuration for each type of device you want to use for development. Each device manufacturer uses a different vendor ID. The example rules files below show how to add an entry for a single vendor ID (the HTC vendor ID). In order to support more devices, you will need additional lines of the same format that provide a different value for the SYSFS{idVendor} property.

Quick fix:

sudo -s adb kill-server adb start-server adb devices 

Permanent fix:

$ lsusb Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 002: ID 093a:2510 Pixart Imaging, Inc. Hama Optical Mouse Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 002: ID 18ea:0004 Matrox Graphics, Inc. TripleHead2Go [Digital Edition] Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 010: ID 0bb4:0c87 High Tech Computer Corp.  <<<<<<<< my HTC phone Bus 001 Device 008: ID 046d:0817 Logitech, Inc. Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub 

Note 0bb4 is the vendor ID. Next, create /etc/udev/rules.d/51-android.rules with the following lines:

SUBSYSTEM=="usb", SYSFS{idVendor}=="0bb4", MODE="0666" 

Final steps:

sudo chmod a+r /etc/udev/rules.d/51-android.rules sudo udevadm control --reload-rules 

Done.

A list of popular vendor IDs: