IT Systems, Networks, Security and Education
A course in using the Linux command line and an introduction to Python.
This is post 1 of 11 in the series “The Linux Command Line” Objectives Understanding Linux file systems, users and groups, and permissions. Becoming familiar with basic navigational commands, built-in and binary executables, and advanced functions available at the bash command line. Learning how to use special permissions on executables and directories to manage availability …
This is post 2 of 11 in the series “The Linux Command Line” Let’s be clear: the structure of directories in any OS is a directory tree. You, I and everyone will want to call it a “file system.” That’s okay, and the other kids usually won’t laugh at you. But formally, a file system …
This is post 3 of 11 in the series “The Linux Command Line” Boot, login, and start Secure Telnet/Secure Shell or PuTTY. Log in with your UNM user name and password. Check Your Shell Command: echo $SHELL Your answer may be: /bin/sh # the Bourne shell /bin/csh # the C shell /bin/bash # the Bourne …
This is post 4 of 11 in the series “The Linux Command Line” You can change your own password, or if you are an admin you can also change the passwords of other users. To change the password for your currently logged-in user: passwd # Enter existing password # Enter new password # Enter new …
This is post 5 of 11 in the series “The Linux Command Line” When you start a shell session, it opens in your home directory. This is true in all OSs, and even the paths are similar. In Windows: C:\Users\username\ In Mac: /Users/username/ In Linux: /home/username/ or /users/username/ Why home? It keeps your stuff segregated …
This is post 6 of 11 in the series “The Linux Command Line” Where user information is stored User names and primary groups are stored in /etc/passwd. To see this file: cat /etc/passwd This file can be directly edited, although this is not recommended. The format of each line is: User name (normally all lower …
Where group information is stored Group information is stored in /etc/group. This file should be changed with the usermod, groupadd and groupmod commands. The format of each line is: Group name Group password (hardly ever used) Group ID User names (separated by commas) Each field is separated by a colon.
This is post 7 of 11 in the series “The Linux Command Line” When a new user is created, the default files and directories that are created are stored in /etc/skel. This directory can be modified to fit your needs. Modifications will only affect new users; they do not change anything for existing users.
This is post 8 of 11 in the series “The Linux Command Line” Examine root’s user profile and PATH characteristics. Become root: sudo su – Enter the command: ifconfig as root, and you’ll see your IP address (among other things). Just to be sure, run: whoami And while you’re at it, check your (root’s) group …
This is post 9 of 11 in the series “The Linux Command Line” Both sudo and su are highly dangerous. The sudo command is used to run a following command as the super-user. Think “super-user do.” It lets regular users do rootly thing, like: sudo cat /etc/shadow You’ll be prompted for a password: Your Password. …