Traditionally, UNIX systems allow any host, from anywhere, to connect to its various services (such as telnetd, ftpd, POP/IMAP). Since the majority of NRC’s systems are connected directly off the Internet, it means anyone may have access to the systems and their services. To restrict who has access to which service, TCP wrappers are used … Read more
SSH (Secure SHell) is a protocol used to provide secure connections between two hosts. The secure connection is provided by encrypting the entire session between the two systems. Each system has a pair of keys: a private and a public key. The keys are created at the same time, so they do have a direct … Read more
To system administrators: use the rules. make sure every user uses a password. limit the number of people who know the root password, to at least one more than yourself, but not too many. use the root account only when performing system administration work.
File permissions have already been introduced in the File System article. USE them. If you have a file, or a directory which contains sensitive information, close it to everyone but yourself (using chmod 700 file). If a file is to be run, but the contents should not be seen by any user, do not allow … Read more
A shell is a program that interprets and runs the commands typed at the console by the user. The shell sends requests to the kernel, which executes them. UNIX comes with various shells, the most common being the C Shell, the Bourne Shell and the Korn Shell. IRIX adds the Tenex Shell. linux includes both … Read more
UNIX’s philosophy is the same as the C language’s: it assumes users know what they are doing!!!
The UNIX system is mainly composed of three different parts: the kernel, the file system, and the shell. [The kernel] is that part of the system which manages the resources of whatever computer system it lives on, to keep track of the disks, tapes, printers, terminals, communication lines and any other devices. The file system … Read more
Check the hardware. When you’re beginning the troubleshooting process, check all your hardware to make sure it’s connected properly, turned on, and working. If a cord has come loose or somebody has switched off an important router, this could be the problem behind your networking issues. There’s no point in going through the process of … Read more
Understanding the mathematics that govern our daily lives, and how you can use it to your advantage. There’s something irresistible in the idea that everything that seems vague, random and unpredictable in our lives can be explained with mathematics. That there’s an equation tucked away in some seldom-visited corner of academia able to provide answers … Read more
The United Arab Emirates (UAE) plans to send an unmanned spacecraft to the Moon in 2024, according to a senior official. Sheikh Mohammed bin Rashid Al Maktoum, the ruler of Dubai, announced the news, which follows the launch of a Mars probe earlier this year by the UAE. “It will be an Emirati-made lunar rover … Read more