Note: this question is a duplicate of Unable to reset password in Recovery Mode, but the solution mentioned there was to reinstall the OS, which is not really the solution I'm striving for if there is any other way to solve this.
Due to a problem with my keychain mentioned here OS X is repeatedly asking for login keychain password, I now wanted to reset my user folder permissions by booting in recovery mode and then via the
But none of my disks shows up here:
(My Mac, which I got with Mountain Lion, is meanwhile on El Capitan. I have only one user, which is also the admin user. Beside the keychain issue I linked above, I haven't noticed any other issues with my system / users so far.)