1. EMT 2390L Lecture 5 Dr. Reyes Reference: The Linux Command Line, W.E. Shotts

2. Outline Ownership Change Mode Changing Identities Processes Environment Variables

3. Ownership Files permissions are divided in three levels: owner, group, everybody o ls -l id command is used to find out information about your identity o id

5. Change Mode chmod - change the mode or permissions of a file or directory Permissions represented using octal notation o > foo.txt o ls -l foo.txt o chmod 600 foo.txt o ls -l foo.txt o chmod 777 foo.txt o ls -l foo.txt

6. Changing Identities su command allows you to log in as another user o su – o su – username sudo command allows you to execute commands as a different user, usually a superuser in a controlled way o sudo chown command is used to change the owner of a file passwd command is used to change the password

7. Processes When the system starts, the kernel executes the init program init runs several shell scripts that start the services When a program launch another program, these are know as parent process and child process respectively. Each process is assigned a process ID (PID) ps – command used to view a snapshot of the processes o ps o ps x top – command used to view process dynamically o top

8. Controlling a Process Execute the following commands o xlogo o Ctrl + C o xlogo & o ps o jobs o fg %1 o Ctrl + Z o ps (Check the PID of xlogo) o kill PID (where PID is the Process ID of xlogo) o xlogo & o kiallall xlogo

9. Commands pstree – command used to display the processes parent/children relationship o pstree vmstat – outputs a snapshot of system resource usage including memory and disk o vmstat printenv – displays a list of the environment variables o printenv o printenv USER o printenv | grep USER o echo $USER

10. Important Environment Variables (cont.)

11. Important Environment Variables

12. Modifying the Environment Locate the configuration files that needs to be modify such as.bash_profile,.bashrc or.profile Create a backup Use a text editor, make the changes, and save them Use the command source followed by the name of the file you just changed to activate the changes o source.profile

13. Assignments Check the class OpenLab site for new Labs Check Blackboard for new Quizzes Midterm Review