This book shows usage of the Linux operating system at expert level. The basics are covered in a profound way while the knowledge necessary for professional work are given. The commands of File System & Content Manipulation take place in main text. Advanced topics such as regular expressions & AWK together with editors such as vi/vim, nano and emacs are explained. The compression & archive tools such as zip, gzip & bzip2 are in contents. The wget & curl tools are covered for data transfers. The package managers are explained in general & some details about yum and apt are explained by practical examples.