Another reason I wrote this book has to do with the fact that I write the monthly "Paranoid Penguin" security column in Linux Journal Magazine. About a year and a half ago, I realized that all my pieces so far had something in common: each was about a different aspect of building bastion hosts with Linux.
By then, the column had gained a certain amount of notoriety, and I realized that there was enough interest in this subject to warrant an entire book on Linux bastion hosts. Linux Journal generously granted me permission to adapt my columns for such a book, and under the foolish belief that writing one would amount mainly to knitting the columns together, updating them, and adding one or two new topics, I proposed this book to O'Reilly and they accepted.
My folly is your gain: while "Paranoid Penguin" readers may recognize certain diagrams and even paragraphs from that material, I've spent a great deal of effort reresearching and expanding all of it, including retesting all examples and procedures. I've added entire (lengthy) chapters on topics I haven't covered at all in the magazine, and I've more than doubled the size and scope of others. In short, I allowed this to become The Book That Ate My Life in the hope of reducing the number of ugly security surprises in yours.