LINUX File System Overview and Commands

LINUX File System Overview

• LINUX uses a hierarchical tree structure for its filesystem, starting from the root directory (/).
• Each directory can have multiple child directories but only one parent directory.
• Paths can be absolute (from root) or relative (from the current directory).

Listing LFS Directories

• The ls command displays current directory contents; it lists visible files and directories by default.
• Hidden files (starting with a period) can be shown using ls -a, which lists all entries, including . (current) and .. (parent) directories.

I-node Structure

• An i-node is a data structure that stores file metadata, including ownership, location, and pointers to file blocks.
• Each partition has its own set of i-nodes, allowing files with the same i-node number in different partitions.
• Use ls -i to display i-node numbers for files in the current directory.

Hard and Symbolic Links

• Links are a file name combined with an i-node number, allowing access to files from different locations.
• Hard links are direct duplicates of the original file; symbolic links point to the original file's location.
• Create symbolic links with ln -s existing_file new_file.

Finding Files

• Use the find command to search for files by name within a directory tree.
• Example to find .txt files: find /home -name "*.txt" -print.
• Find can filter files by type, permissions, size, etc., and can execute commands on found files with the -exec option.

Finding Text in Files

• The grep command searches for text patterns in files.
• Basic syntax: grep options pattern files, where options can modify behavior (e.g., -c counts matches, -i ignores case).
• Combine grep with find to search through files in directory trees (e.g., grep hello \find . -name "*.txt" -print``).

Sorting Files

• The sort command organizes file contents alphabetically or numerically.
• To output sorted results to another file, use redirection (e.g., sort input1.txt input2.txt > output.txt).
• The uniq command removes adjacent duplicate lines from a file, often used after sort for streamlined output (e.g., sort input.txt | uniq > output.txt).