SSH Public Key Based Authentication on a Linux/Unix server

last updated in Categories CentOS, Debian Linux, FreeBSD, Gentoo Linux, Howto, Linux, Linux desktop, Linux laptop, OpenBSD, RedHat/Fedora Linux, Solaris, Suse Linux, Sys admin, Tips, Ubuntu Linux, UNIX

The SSH protocol recommended a method for remote login and remote file transfer which provides confidentiality and security for data exchanged between two server systems. The SSH depends upon the use of public key cryptography. The OpenSSH server offers this kind of setup under Linux or Unix-like system. This how-to covers generating and using ssh public keys for automated usage such as:

  1. Automated Login using the shell scripts
  2. Making backups
  3. Run commands from the shell prompt and more
  4. Login without password

Linux/ FreeBSD GNU GCC Common option for C compiler

last updated in Categories Linux, UNIX

gcc is a GNU project C and C++ compiler for Linux, UNIX, FreeBSD etc. From the wikipedia:

GCC is a key component of the GNU toolchain. As well as being the official compiler of the GNU system, GCC has been adopted as the standard compiler by most other modern Unix-like computer operating systems, including Linux, the BSD family and Mac OS X. GCC has been ported to a wide variety of computer architectures, and is widely deployed as a tool in commercial and closed development environments.

Common gcc options:

cc -E :preprocessor
cc -S :create or show assembly coding
cc -o :object filename
cc -g :debug info
cc -O :optimized code
cc -O2 :optimized code with optimization level increased
cc -Wall :create or show all warning
cc -D_SYMBOL_ : Symbol for prerpcessor

You can use gcc instead of cc.