OPS 102: Introduction to Operating Systems

Connection to Matrix

• Seneca students have access to a Matrix server, a cluster of computers running CentOS (a version of Linux), which can be accessed remotely using VPN or SSH.
• To connect to Matrix, students need to download and install a VPN client or use SSH (secure shell) protocol.
• Connection to Matrix is required for practicing Linux commands, performing Linux labs, and doing quizzes/tests.

File Systems

• A file system is a method of organizing and retrieving files efficiently from a storage medium (e.g., hard disk).
• Both Linux and Windows are hierarchical file systems, where files are organized in folders and subfolders.
• In Linux, the topmost directory is the root (/), and there are no drive letters like C: or D.
• In Windows, the File System hierarchy starts from drives: C:, D:, etc.

Files and Folders (Directories)

• Folders are containers that can have files and other folders (subfolders).
• Files are used to save user data, and can be of many different types (e.g., Word documents, XL files, PPT files).
• File types are identified by their extensions (e.g., .docx, .exe, .txt).
• A specific program or application is required to open each file type.

File Names

• Unix/Linux is case sensitive, whereas Windows is not case sensitive for file names.
• Adopt a consistent file naming scheme, and avoid non-alphanumeric characters and spaces in file names.

Linux Hierarchical File System

• The standard Linux distribution follows a specific directory structure, with multiple top-level directories (e.g., /bin, /home, /usr, /etc, /var, /tmp, /dev, /opt).

Current Working Directory

• The current working directory is the folder/directory where you are currently working.
• The cd command is used to change the current working directory.

Paths

• A path specifies a unique location of a file or directory in the file system.
• There are three ways of specifying pathnames: absolute, relative, and relative to home.
• Examples of paths: /home/cory, C:\Users\Natali, /home/jono/work.

Changing the Current Working Directory

• The cd command is used to change the current working directory.
• You can use any type of paths (absolute, relative, or relative to home) with the cd command.

Listing the Contents of a Directory

• In Linux, the ls command is used to display a list of files and subdirectories in the current directory or any other directory.
• In Windows, the dir command is used to list the contents of a directory.
• Options can be used with these commands to customize the output.

File Systems and Matrix

• Connection to matrix: Seneca students have access to both Windows and Linux OS, with Linux available on the matrix server.
• Matrix server consists of several computers running CentOS, a version of Linux, connected together to form a cluster.
• All registered students in this course have access to an account on Matrix for practicing Linux commands, performing Linux labs, and doing quizzes/tests.

Connecting to Matrix

• As of September 2020, students must connect to the Seneca Global Portal VPN to access their matrix Linux account when off-campus.
• Download and install the VPN client from https://students.senecacollege.ca/spaces/186/it-services/wiki/view/1025/student-vpn.
• Connect to matrix from any Seneca lab workstation or personal computer using ssh (secure shell) protocol.
• Commands: who prints information about the current logged-in user, whoami prints the name of the current user, cls or clear clears the terminal screen, and tree shows the folder hierarchy in a tree format.

File System

• A file system is a method of organizing and retrieving files efficiently from a storage medium, such as a hard disk.
• Both Linux and Windows are hierarchical file systems, with files organized in folders and subfolders.
• In Linux, the topmost directory is the root (/), and all files and directories appear under it.
• There are no drive letters like C, D, etc. in Linux.

Files and Folders (Directories)

• Virtually everything in a modern computer system is a file or a folder.
• Folders are containers that can have files and other folders (called sub-folders).
• Examples of folders: Home folder, Desktop folder, Root Folder.
• Files are used to save user data, and can be of many different types, such as Word documents, XL files, PPT files, etc.
• File types are identified by their extensions (3 or 4 last characters after a dot).

Navigation and Listing

• cd command changes the directory to the parent of the current directory.
• cd /home/ops102 changes the directory to the location specified by an absolute path.
• ls command lists the contents of a directory in Linux, and dir is the parallel command in Windows.
• ls -l command determines the type of file and looks at the first character in the detailed listing.

File Types in Linux

• ls -l command displays file types:
  • - indicates a regular file.
  • b or c indicates a device file.
  • d indicates a directory.
  • l indicates a symbolic link.
  • p indicates a pipe, used to communicate between processes on the same server.
  • s indicates a socket, used to communicate between processes on the same or different servers.