My mbp has a serious problem and cannot boot or proceed to a normal osx startup. I can only get into unix, pressing command-s during startup. From this unfriendly(for me) environment, I want to find a way to completely delete the hard disk, before I sell my mbp for spare parts. I don't want to give the ssd with my personal information inside it, at least I want to trash everything and disappear anything from my data. Last time I tried to type some commands, I remember having several 'denies' from system, due to permissions matters, as I just got into unix, I am not administrator or anything like that. But, I think I should have a way to delete my files. So please give me all the alternative ways, commands, pathways, to be able, in any case, to proceed to extermination of my files inside the internal mbp disk. I 'll write them down, and I will try them all. I hope that some of these commands could do the job.