LINUX FIELD GUIDE // 01

Create and audit Linux files with deliberate permissions

Inspect location and ownership before creating files, then verify directory and file permissions separately.

Scenario

A shared server contains unfamiliar files and permissions that must be handled safely.

BEFORE YOU START

Prerequisites and boundaries

Practice as a non-root user in a disposable directory.
Identify the user and group that should read or modify the target.
Remember that directory execute permission controls traversal, not program execution.

OPERATIONAL REASONING

The goal is not merely to memorize commands. Each inspection, change, and verification step reduces a different failure mode.

Relative paths depend on the current directory, so pwd is part of the safety check.

Directories need traversal permission while regular files usually do not need an execute bit.

ls and stat provide complementary views of ownership and permission bits.

STANDARD PROCEDURE

Confirm the location, create the hierarchy and file, then restrict directory traversal and file access separately.

INCIDENT RESPONSE

Locate and inspect the file before restricting it to its owner, then verify the final permission bits.

COMMON FAILURE MODES

A recursive chmod removed execute permission from directories and made them inaccessible.
A relative path created or changed files in the wrong directory.
Permissions were tightened but ownership still granted access to the wrong account.

VERIFICATION