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

Outline Ownership Change Mode Changing Identities Processes Environment Variables

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

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

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

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

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

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

Important Environment Variables (cont.)

Important Environment Variables

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

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