I cant init Google Cloud SDK on Ubuntu

I downloaded Google Cloud SDK for python on my Ubuntu. (https://cloud.google.com/sdk/docs/quickstart-linux#before-you-begin)

Then I followed the steps from the page but when I run

gcloud init

I get this

Could not setup log file in /home/ariel/.config/gcloud/logs, (IOError: [Errno 13] Permission denied:'/home/ariel/.config/gcloud/logs/2016.05.25/11.54.37.438036.log') Welcome! This command will take you through the configuration of gcloud.

ERROR: (gcloud.init) Failed to create the default configuration. Ensure your have the correct permissions on: [/home/ariel/.config/gcloud/configurations]. Could not create directory [/home/ariel/.config/gcloud/configurations]: Permission denied.

Please verify that you have permissions to write to the parent directory.

PS: Then I found this other file https://cloud.google.com/appengine/downloads#Google_App_Engine_SDK_for_Python (seems to be the same but it is 40.2MB and the one I used was 7.5MB)

Thanks !Ariel