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, …
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 …
umask is a Unix shell built-in command that automatically sets file permissions on newly created files. The umask command can be confusing to use because it does work as a mask. In other words, the user sets the permissions that he/she does not want in the umask. To calculate permissions that will result from specific …
List Logged In Unix Users Unix has many commands to list users who are logged in. These commands include ‘w,’ ‘who,’ and ‘users:’ $ w 9:51PM up 99 days, 5:39, 2 users, load averages: 0.83, 0.90, 0.90 USER TTY FROM LOGIN@ IDLE WHAT will p0 c-66-164-235-73. 8:11AM – w spencer p3 c-66-164-235-73. 8:26PM 1:24 pine …
Bootable distributions of the Linux operating system are becoming very popular for use in securing networks, testing network security, and conducting forensics after suspected intrusions. Local Area Security Linux Local Area Security Linux is a ‘Live CD’ distribution with a small footprint. Containing over 200 information security and administration related tools, as well as a …