Free derivatives of Unix can be easily downloaded via the Internet. This sets Unix apart from other proprietary operating systems like Microsoft Windows. The different Unix versions and Unix-like operating systems available for download include FreeBSD, OpenBSD, Red Hat Fedora Linux, Debian Linux, Ubuntu Linux, and Sun Solaris. Those who are new to Unix or …
UNIX is one of the most important operating systems ever developed. What made Unix stand out in the crowd of countless other operating systems is that it was a competent operating system that was extremely affordable and worked on low cost hardware. Economics definitely played a large part in UNIX’s popularity and today it is …
Top is a small, but powerful program on both Unix and Linux systems. Its purpose is to allow users to monitor processes on their system. It has two main sections. The first displays general information such as the load averages, number of running and sleeping tasks, and overall CPU and memory usage. The second main …
A rootkit is a type of computer malware that is created to hide programs or other computer processes from detection from both users and antivirus software programs. Once installed, a rootkit will typically obtain administrator or higher-level permissions on the infected computer. Although rootkits originated with the UNIX operating system by providing root access to …
A signal is a message that can be sent to a running process. Programs, users, or administrators can initiate signals. For example, the proper method of telling the Internet Daemon (inetd) to re-read its configuration file is to send it a SIGHUP signal. For example, if the current process ID (PID) of inetd is 4140, …
The total number of Unix commands is immense. No normal user or system administrator would ever need to know them all. The Unix commands available to you will vary based upon several factors: The version of Unix you are using (FreeBSD, Linux, Solaris, AIX, HP-UX, OpenBSD, etc…) The Unix shell you are using (sh, csh, …
Unix file permissions are based upon an octal code. Unix file permissions are stored in a ten character array. The first character of the file permissions stores the file type. The standard file types are: Character Meaning – Plain file d Directory c Character device b Block device l Symbolic link s Socket = or …
A restricted shell is a Unix shell that has been modified to allow the Unix shell user to do fewer things than a normal shell would allow him to do. It may allow the user to run only certain programs. It may stop the user from changing directories. Many sites run their own restricted shells …
One of the best methods to capture a Unix terminal session is to use the `script` command. In this example we start a script session, run a couple of commands, and then use the `exit` command to stop capturing the terminal session: $ script Script started, output file is typescript $ pwd /home/will $ ps …
A computer process is a computer program that is executing and has a unique process identification or PID. On the Unix Operating System (OS), a process may be running in the background, foreground, or be in a suspended state. On Unix, the OS shell will not return the prompt to the end-user until the current …