What Are Bind Mounts and Why Use Them A bind mount is a special type of mount in Linux that allows you to create a mirror of a directory structure in another location. It involves mounting an existing filesystem somewhere else while retaining the same permissions and semantics. The key difference compared to symbolic links…
Demystifying Linux File Permissions As a Linux system administrator, fully grasping Linux file permissions is crucial for properly securing and maintaining access control across your systems. However, the concepts around owners, groups, and access modes can sometimes become confusing. In this comprehensive guide, we will unravel the mystery around Linux file permissions by exploring key…
Preserving Extended Attributes When Moving Data When migrating data in Linux environments, special care must be taken to preserve extended file attributes (xattrs), which often contain critical security metadata. If xattrs are not properly retained during data migration, the result can be catastrophic security gaps and compliance violations in the new environment. What are Extended…
What are SELinux and Extended Attributes? SELinux (Security-Enhanced Linux) is an access control mechanism implemented in the Linux kernel that provides rigid controls over files, processes, and users through security policies. It enforces rules over what subjects such as users and processes can access which objects like files and directories. SELinux policies comprehensively manage access…
Understanding Linux File Permissions On Linux systems, each file and directory has assigned permissions that determine which users can access, modify, or execute it. Understanding how permissions work is crucial to properly securing your system. Permissions can be viewed, set, and altered using various commands. Defining file ownership and permissions All files and directories are…
Catching Errors in sed Detecting errors is the first step towards handling them gracefully in sed scripts. The exit code of the last command executed is stored in the $? variable. Checking this variable after running sed allows detecting errors via non-zero exit codes. Using Exit Codes to Detect Errors A simple way to check…
Understanding In-Place Editing In-place editing refers to modifying a file directly on disk, rather than creating a separate output file with the changes. The sed utility allows performing fast in-place edits on text files using regular expressions and editing commands. Typical use cases where in-place editing with sed excels include: Mass find-and-replace operations across multiple…
Mitigating Security Risks when Using sed The stream editor sed is a powerful tool for text manipulation and transformation. However, if used carelessly, sed can introduce security vulnerabilities into applications that allow arbitrary user input. Malicious users may attempt to inject sed control sequences or exploit the evaluation of unsafe functions in an attempt to…
Why Escaping Characters Matters in sed The sed text processing utility interprets certain characters in a special way during its substitution commands. Characters like the forward slash (/), backslash (\), and dollar sign ($) have predefined functions in the syntax of sed substitution, so they need to be escaped if you want them to be…
Understanding Argument Parsing in Bash In Bash scripts, arguments refer to the data passed to commands, programs, functions, and scripts. Understanding how Bash handles argument parsing is crucial for writing robust scripts that accept input correctly. There are two main types of arguments in Bash: Positional Arguments – Arguments that are mapped to variables based…