Use the Linux Command Line

On This Page Introducing the Linux Command Line Navigating Directories Administering Users and Groups Using File Permissions back to top Introducing the Linux Command Line Linux command line available from the Terminal emulation program Single-click the above icon on the launch panel (taskbar) Alternatively, you can launch from the Main Menu Programs => System => GNOME terminal Once you have a command line, you can use the UNIX help facility: man commandName For example, to view the man(ual) page for the cat command: man cat To quit viewing a man page, press the q (for quit) key back to top Navigating Directories When the terminal is first opened, you are located in your home directory: /home/cis164 You can verify the location using pwd (print working directory) pwd You can list the files in the current directory using ls ls View a file using any of the commands: cat, more or less cat exercise2.txt Change up one directory level: cd .. (change directory) cd .. Change to a subdirectory level: cd filename cd cis164 Change to the root of the file system: cd / cd / Change to any location in the file system: cd path cd /home Change to your home directory cd ~ cd ~ back to top Administering Users and Groups User Accounts and the Superuser Security in Linux is controlled with user accounts, just like Windows Each account has a login and password One user, known as the superuser, can do anything in the system -- even destroy it The account name for the superuser is "root" Normally, one should not log in as root The root login is strictly for configuration and administration of a system Sometimes need to switch temporarily to the root account Use su (switch user) command su -l root When finished as the superuser, use the exit command exit File Ownership Every file and directory has an owner Default owner is root Owner of the file grants permission to other users to read, modify, delete, or execute it Owner can decide that no other users should be granted access to a file The exception is the superuser A user cannot take away access from the superuser Owner (or root) can change ownership of a file or directory Type chown newOwner filename where: newOwner is the username you want to change ownership to filename is the name of the file or directory chown root myfile.txt Groups and Belonging Every user belongs to one or more groups Default group is users Every file and directory also has a group owner One can see the individual and groups by using the ls -l command ls -l Owners (or root) can change the group of a file or directory Type chgrp newGroup filename where: newGroup is the group you want to change ownership to filename is the name of the file or directory chgrp mysql myfile.txt The superuser can add users to additional groups Type useradd -g newGroup userName where: newGroup is the group you want to add to the user userName is the users account name useradd -g mysql cis164 More Information Sys. Admin back to top Using File Permissions One can see file permissions using the ls -l command First digit is the file type Next 3 digits are the Owner permissions Next 3 digits are the Group permissions Next 3 digits are the Others (everyone) permissions If a permission is missing for an owner, group of other, it is represented by - (dash) File permissions are altered with the chmod command followed by octal value for each user type and the filename, where: Read = 4 Write = 2 Execute = 1 For example: chmod 755 exercise2.txt Above example gives full permission for the owner, read and execute access for the group and others More Information CHMOD (1) The One Page Linux Manual back to top Home | WebCT | Announcements | Schedule | Expectations | Syllabus | Help | FAQ's | HowTo's | Links Last Updated: 7/16/2003 4:45:47 PM