adb devices command not working

One thing I didn't try was editing /etc/udev/rules.d/70-android.rules. Is that likely to be the issue?

Any particular reason why you didn't do that? To answer the question - YES! The udev rules are what informs Ubuntu what your device is and allows user-space tools to therefore access it.

You will not be able to use adb without correctly following the instructions.

With that in mind however, you don't say what version of Ubuntu you're using but I had issues with 10.10 - let me know if you need me to post the contents of my rules file.

Don't worry about running adb via sudo, you don't need it. The MODE="0666" from the udev rule allows you to access the device as any user.

EDIT:

Don't forget to reload the rules:

sudo udevadm control --reload-rules

EDIT #2:

As @Jesse Glick correctly points out, if adb is already running in daemon mode, you'll also need to restart it for this to work:

sudo adb kill-server

I've used sudo here, since that will guarantee that adb will be killed , and it's the officially supported method to stop the server. It will be automatically restarted the next time adb is used, but this time with the correct environment.

You need to restart the adb server as root. See here.

On my Gentoo/Funtoo linux system I am having similar problems:

I gotting always not the correct device description and insufficient permissions:

# sudo ./adb devicesList of devices attached ????????????    no permissions# ./adb usberror: insufficient permissions for device

For me helps the howto from Google. In my case I needed to add the udev rule:

# cat /etc/udev/rules.d/51-android.rules SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", MODE="0666", GROUP="plugdev" 

and setting up the filesystem rights

# chmod a+r /etc/udev/rules.d/51-android.rules

After replugging my smartphone the access to the phone was successful, it also appears now in Eclipse' Android Device Chooser:

# sudo ./adb devicesList of devices attached 3XXXXXXXXXXXXXC device# sudo ./adb usbrestarting in USB mode

You also have to check the membership of your user to the plugdev-group.