I just experienced this bug on Ubuntu 13.04 amd-64 desktop. The following appeared in /var/log/auth.log after attempting to install a VirtualBox extension package:
Running gksu-properties, it seems that the 'authentication mode' is originally set to 'su', which does not work when there is no root administrator password set (default + strongly recommended for Ubuntu desktop installation, see https://help.ubuntu.com/community/RootSudo). Switching the option in gksu-properties to 'sudo' and then using the logged-in user's password fixed the issue.
It seems this default should really be fixed in Ubuntu's default install, but application developers could also call 'gksudo' instead of 'gksu', which seems to use 'sudo' properly regardless of the gksu-properties setting.
I just experienced this bug on Ubuntu 13.04 amd-64 desktop. The following appeared in /var/log/auth.log after attempting to install a VirtualBox extension package:
Jul 30 12:47:54 will-desktop su[9696]: pam_unix(su:auth): authentication failure; logname= uid=1000 euid=0 tty=/dev/pts/5 ruser=will rhost= user=root
Jul 30 12:47:56 will-desktop su[9696]: pam_authenticate: Authentication failure
Jul 30 12:47:56 will-desktop su[9696]: FAILED su for root by will
Jul 30 12:47:56 will-desktop su[9696]: - /dev/pts/5 will:root
Running gksu-properties, it seems that the 'authentication mode' is originally set to 'su', which does not work when there is no root administrator password set (default + strongly recommended for Ubuntu desktop installation, see https:/ /help.ubuntu. com/community/ RootSudo). Switching the option in gksu-properties to 'sudo' and then using the logged-in user's password fixed the issue.
It seems this default should really be fixed in Ubuntu's default install, but application developers could also call 'gksudo' instead of 'gksu', which seems to use 'sudo' properly regardless of the gksu-properties setting.