Now that the UNIX tree-structured file system has been introduced, it would be useful to know how to find our way through the system and how to create files, delete them and rename them. cd: Change Directory To move from one directory to another the cd command is used. Use as: cd [directory] directory may … Read more
This article will deal with how to log on to the UNIX system, and how to log out. Logging On Initially, a user needs to get a userid and, optionally, a password. The userid is typed in at the login prompt, which usually looks like: login: Following the logon, the password prompt will appear: password: … Read more
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