2.0 Operating Systems & Linux Basics Flashcards

Question

# 2.0 Operating Systems & Linux Basics What is the difference between a **host OS** and a **guest OS**?

Answer 1

The host OS runs directly on the physical machine; the guest OS runs inside a VM managed by a hypervisor. ## Footnote Understanding this distinction is important for virtualization concepts.

Answer 2

A hypervisor that runs directly on the hardware, managing guest OSes without a host OS layer. ## Footnote Type 1 hypervisors are often used in enterprise environments.

Answer 3

Cloud providers, data centers, and high-performance virtualization environments. ## Footnote Their efficiency makes them suitable for resource-intensive applications.

Answer 4

A hypervisor that runs inside a host OS as an application, adding another software layer. ## Footnote Type 2 hypervisors are often used for personal or development purposes.

Answer 5

Local development, learning, testing multiple OSes, and running portable VM images. ## Footnote They provide flexibility for users experimenting with different operating systems.

Answer 6

* Hardware efficiency * Agility * Portability (VM image files) * Easy backups * Cost savings * Environment isolation ## Footnote These benefits contribute to the popularity of virtualization in modern IT.

Answer 7

The VM is isolated; mistakes do not impact the main OS. ## Footnote This isolation allows for safe testing of new software or configurations.

Answer 8

* Install VirtualBox * Create an Ubuntu VM * Allocate CPU/RAM/disk from host * Install Linux inside the VM * Remember: resources are shared with the host ## Footnote Following these steps ensures a successful VM setup.

Answer 9

A single-root hierarchical tree structure starting at `/`. ## Footnote This structure allows for organized file storage and access.

Answer 10

Linux has one root (`/`); Windows has multiple root drives (`C:\`, `D:\`, etc.). ## Footnote This affects how files are organized and accessed.

Answer 11

**Everything in Linux is a file**, including text files, commands, directories, and devices. ## Footnote This unifies the way resources are handled in the system.

Answer 12

A reference to any resource treated as a file (documents, devices, directories, commands). ## Footnote File descriptors are essential for managing input/output operations.

Answer 13

Each user gets isolated disk space and their own configurations and permissions. ## Footnote This enhances security and customization for each user.

Answer 14

A computer-readable executable file. ## Footnote Binaries are essential for running applications and commands.

Answer 15

Historically due to storage constraints, leading to separation between root binaries and user-installed binaries. ## Footnote This organization helps manage system resources effectively.

Answer 16

Software installed by the user, such as Docker, Minikube, Java; available to all users. ## Footnote This directory is for user-installed software that is not part of the default system.

Answer 17

* `/usr/local`: for programs split into multiple components * `/opt`: for programs not split (self-contained) ## Footnote This distinction helps in managing software installations.

Answer 18

Device files that apps and drivers use to communicate with hardware. ## Footnote This directory is crucial for hardware interaction.

Answer 19

System and application log files. ## Footnote Logs are essential for monitoring system performance and troubleshooting.

Answer 20

Cached data generated by applications. ## Footnote Caching improves performance by reducing the need to regenerate data.

Answer 21

Automatically created mount points for removable devices like USB drives or CDs. ## Footnote This directory simplifies access to external storage.

Answer 22

Temporary mount points, historically used by sysadmins for manual mounts. ## Footnote This allows for flexible management of file systems.

Answer 23

File names beginning with a dot (`.`), also called dotfiles. ## Footnote Hidden files are often used for configuration settings.

Answer 24

To avoid accidental deletion and store system or application configuration. ## Footnote This helps maintain system stability.

Answer 25

CLI is the interface where commands are entered; the Terminal is the GUI window displaying the CLI. ## Footnote Understanding this distinction is important for effective command line usage.

Answer 26

It’s faster, more efficient for bulk tasks, supports more formats, and servers often lack a GUI. ## Footnote CLI tools are essential for automation and remote management.

Answer 27

Root has full system privileges; regular users are limited for safety. ## Footnote This separation enhances security and prevents accidental system damage.

Answer 28

Allows a regular user to temporarily run commands with root privileges. ## Footnote This is crucial for performing administrative tasks without logging in as root.

Answer 29

A compressed archive containing the program and metadata about its dependencies. ## Footnote Packages simplify software installation and management.

Answer 30

Most apps require other libraries to function; the package manager installs them automatically. ## Footnote This ensures that all necessary components are available for software to run.

Answer 31

* Downloads and installs software * Resolves dependencies * Ensures package authenticity * Places files in correct directories * Updates installed software ## Footnote Package managers streamline software management.

Answer 32

A user-friendly package manager (Advanced Package Tool) preinstalled on Ubuntu. ## Footnote APT simplifies the installation and management of software on Debian-based systems.

Answer 33

To refresh the local package index with the latest changes from repositories. ## Footnote This ensures you are installing the most current versions of software.

Answer 34

A database storing metadata about available packages. ## Footnote This index is essential for the package manager to function correctly.

Answer 35

APT is more user-friendly with cleaner output; APT-GET has more commands but requires additional flags for nicer output. ## Footnote Both tools serve similar purposes but differ in usability.

Answer 36

A GUI-based app store for installing, removing, and updating software on Ubuntu. ## Footnote This provides a user-friendly interface for software management.

Answer 37

A universal Linux packaging system where each snap includes its app and all dependencies. ## Footnote Snap packages simplify installation across different Linux distributions.

Answer 38

* Self-contained packages * Works across distros * Automatic updates ## Footnote These features enhance usability and convenience.

Answer 39

* Larger installation size * Additional runtime overhead ## Footnote These factors can affect system performance.

Answer 40

* Snap includes dependencies; APT shares dependencies * Snap is universal; APT is distro‑specific * Snap auto‑updates; APT updates manually ## Footnote Understanding these differences is crucial for effective package management.

Answer 41

To install software not available in official repositories or newer versions. ## Footnote This expands the available software options for users.

Answer 42

Adds a new source to `/etc/apt/sources.list`, allowing APT to install from it. ## Footnote This is essential for accessing additional software packages.

Answer 43

A community-run repository allowing developers to distribute updated or experimental software. ## Footnote PPAs provide access to software that may not be in the official repositories.

Answer 44

* Potential security issues * Quality concerns * Upgrade problems during major Ubuntu releases ## Footnote Users should exercise caution when adding PPAs.

Answer 45

APT and APT-GET. ## Footnote These tools are essential for managing software on Debian systems.

Answer 46

YUM (or DNF in newer versions). ## Footnote These tools facilitate software management on Red Hat systems.

Answer 47

Primarily based on the package manager ecosystem they prefer to maintain. ## Footnote This choice impacts system administration practices.

Answer 48

Only minor differences; they share most concepts and tools. ## Footnote This similarity simplifies the learning curve for users transitioning between distros.

Answer 49

Servers typically do not have a GUI; all tasks must be done through command line. ## Footnote Mastery of CLI is essential for effective server management.

Answer 50

It allows quick, efficient edits without opening GUI tools. ## Footnote This efficiency is crucial for productivity in development environments.

Answer 51

* Writing Git commit messages * Editing Kubernetes YAML * Searching logs * Bulk operations * One-line script fixes ## Footnote CLI excels in situations requiring speed and precision.

Answer 52

Built‑in command‑line text editors. Vi is the most widely distributed; Vim (“Vi IMproved”) is an enhanced version. ## Footnote Vim is designed for efficient text creation and editing.

Answer 53

It is designed to make creating and editing text highly efficient using modes and keyboard shortcuts. ## Footnote Vim's efficiency is a key reason for its popularity among developers.

Answer 54

* Command Mode * Insert Mode ## Footnote These modes dictate how users interact with the text editor.

Answer 55

You cannot type text; keystrokes are interpreted as commands (navigate, delete, search, undo, etc.). ## Footnote Command Mode is essential for executing commands without inserting text.

Answer 56

You can type and edit text freely; pressing `Esc` returns to Command Mode. ## Footnote Insert Mode is where actual text editing occurs.

Answer 57

* Saving/quitting files * Editing configs * Searching and replacing text * Editing scripts on servers ## Footnote Vim is often used for quick edits in server environments.

Answer 58

* Username * UID (User Identifier) ## Footnote These identifiers are crucial for user management and permissions.

Answer 59

Username can change; UID is fixed permanently. ## Footnote This distinction is important for user management.

Answer 60

System-level authentication and tracking user activity. ## Footnote UID plays a critical role in security and user identification.

Answer 61

Always UID 0. ## Footnote The root user has unrestricted access to the system.

Answer 62

A non-human system user created to run specific services or applications (e.g., mysql user). ## Footnote Service accounts enhance security by limiting access.

Answer 63

For security—root has unrestricted access; compromising a root-running service compromises the system. ## Footnote Running services as root increases vulnerability.

Answer 64

Linux users are local to each machine; Windows domain accounts are centrally managed. ## Footnote This difference impacts how user permissions are handled.

Answer 65

For traceability and per-user permission control. ## Footnote Shared accounts can lead to security and accountability issues.

Answer 66

A list of all user accounts, one per line; readable by all users but writable only by root. ## Footnote This file is essential for user management in Linux.

Answer 67

At user level or group level (recommended for multiple users). ## Footnote Group-level permissions simplify management for teams.

Answer 68

Always GID 0. ## Footnote The root group has special privileges in the system.

Answer 69

* `useradd`: low-level, requires manual options * `adduser`: interactive, user‑friendly, autogenerates configs/home directory ## Footnote Understanding these commands is crucial for user management.

Answer 70

* Create: `adduser`, `addgroup`, `useradd`, `groupadd` * Delete: `deluser`, `delgroup`, `userdel`, `groupdel` ## Footnote These commands are fundamental for user and group management.

Answer 71

An owning user and an owning group. ## Footnote Ownership is critical for file permissions and security.

Answer 72

* Read (r) * Write (w) * Execute (x) ## Footnote Understanding these permissions is essential for file security.

Answer 73

* Owner * Group * Others ## Footnote These categories help define access levels for files.

Answer 74

`chown : ` ## Footnote This command is essential for managing file permissions.

Answer 75

`ls -l` ## Footnote This command provides detailed information about file permissions.

Answer 76

Example: `chmod g-w file.txt` (remove write from group). ## Footnote Symbolic permissions are intuitive for managing access.

Answer 77

Example: `chmod g=rwx file.txt` ## Footnote This method allows for precise permission management.

Answer 78

`chmod 740 file` ## Footnote Numeric permissions provide a compact way to set access levels.

Answer 79

Sends one program's output into another program as input. ## Footnote This operator is essential for chaining commands.

Answer 80

Sends command output to a specified file (overwrites it). ## Footnote Redirecting output is a common practice in scripting.

Answer 81

Displays file content one page at a time and allows scrolling. ## Footnote This tool is useful for viewing large files.

Answer 82

It loads only what’s needed—does not read the entire file at once. ## Footnote This efficiency is crucial for performance.

Answer 83

Searches text for patterns and outputs matching lines. ## Footnote Grep is a powerful tool for text processing.

Answer 84

* stdin: input * stdout: output * stderr: error output ## Footnote Understanding these streams is fundamental for command-line operations.

Answer 85

Automate repetitive tasks, maintain configuration history, and perform bulk logic. ## Footnote Shell scripts enhance productivity in system administration.

Answer 86

.sh ## Footnote This extension indicates that the file is a shell script.

Answer 87

`#!` — tells the OS which shell interpreter to run the script with. ## Footnote The shebang is crucial for script execution.

Answer 88

To allow the OS to run them as programs. ## Footnote Making scripts executable is a necessary step in script deployment.

Answer 89

* `sh` (Bourne shell) * `bash` (Bourne Again shell) ## Footnote Different shells offer various features and capabilities.

Answer 90

`variable=value` ## Footnote Variable assignment is fundamental in scripting.

Answer 91

`var=$(command)` ## Footnote This technique is essential for capturing results in scripts.

Answer 92

A shorthand for the `test` command. ## Footnote This syntax simplifies conditional expressions.

Answer 93

* Numeric * String * File test operators ## Footnote Understanding these operators is crucial for effective scripting.

Answer 94

$1, $2, $3, etc. ## Footnote Positional parameters allow scripts to handle input arguments.

Answer 95

All passed arguments as a single string. ## Footnote This is useful for processing multiple arguments.

Answer 96

The number of arguments passed into the script. ## Footnote This allows scripts to adapt based on input size.

Answer 97

* `for` * `while` * `until` * `select` ## Footnote Loops are essential for repetitive tasks in scripts.

Answer 98

Iterates over a list and runs commands for each item. ## Footnote For loops are commonly used for processing lists.

Answer 99

Repeats commands until a condition becomes false. ## Footnote While loops are useful for conditional repetition.

Answer 100

To break scripts into reusable, logical code blocks. ## Footnote Functions enhance code organization and readability.

Answer 101

$1, $2, etc., within the function. ## Footnote This allows functions to accept and process input.

Answer 102

Single Responsibility Principle—each function should do one thing. ## Footnote This principle promotes cleaner and more maintainable code.

Answer 103

Assign meaningful variable names inside the function. ## Footnote Meaningful names improve code clarity.

Answer 104

Use `top` or `htop` to identify processes with high %CPU, then inspect logs or kill/restart the offending process. ## Footnote This helps in pinpointing resource hogs affecting server performance.

Answer 105

* An infinite loop * Runaway script * Memory leak triggering excessive garbage collection * Misconfigured service ## Footnote Identifying the root cause is essential for resolution.

Answer 106

`kill ` for graceful termination; if it does not stop, use `kill -9 ` for forceful termination. ## Footnote This ensures that the process is terminated properly.

Answer 107

Gradually increasing RAM usage for a single process and heavy swap usage over time. ## Footnote Monitoring memory usage is crucial for system stability.

Answer 108

Use `top` sorted by `%MEM` or `ps aux --sort=-%mem`. ## Footnote This helps in identifying memory-intensive applications.

Answer 109

* Services crash * Logging stops * Applications fail to write * Some commands may hang ## Footnote This can lead to significant system instability.

Answer 110

`du -sh *` or `du -sh /var/*` to inspect directories; `df -h` for filesystem usage. ## Footnote Understanding disk usage is vital for maintenance.

Answer 111

Log files growing indefinitely (e.g., `/var/log/syslog`, application logs). ## Footnote Regular log management is necessary to prevent this issue.

Answer 112

A process still holds the file handle open. Restart the service or run `lsof | grep deleted`. ## Footnote This is important for effective disk space management.

Answer 113

/tmp and /var/tmp, but only remove files not actively in use. ## Footnote Caution is advised to avoid disrupting running applications.

Answer 114

Ping by IP. If IP works but hostname fails, DNS is the problem. ## Footnote This method helps isolate DNS-related issues.

Answer 115

DNS resolution. ## Footnote This indicates that the DNS settings may need to be checked.

Answer 116

Incorrect default route or gateway. Check with `ip route`. ## Footnote Proper routing configuration is essential for network connectivity.

Answer 117

The service is not running or not listening on that port. ## Footnote This requires checking the service status and configuration.

Answer 118

Firewall blocking the port or unreachable destination. ## Footnote This necessitates firewall rule verification.

Answer 119

`sudo netstat -tulpn | grep ` or `ss -tulpn`. ## Footnote This is crucial for troubleshooting network services.

Answer 120

Service is bound to localhost only; it won’t accept external connections. ## Footnote This indicates a need for reconfiguration for external access.

Answer 121

Parent directory permissions may not allow traversal (`x` flag missing). ## Footnote This highlights the importance of checking directory permissions.

Answer 122

Missing execute permission (`chmod +x script.sh`) or missing shebang. ## Footnote Ensuring proper permissions and shebang lines is essential for script execution.

Answer 123

Filesystem mounted with `nosuid` or `immutable`. Check with: `lsattr file` → immutable flag (`i`). ## Footnote This requires checking filesystem attributes.

Answer 124

Removed from `sudo` or `wheel` group, or `/etc/sudoers` misconfigured. ## Footnote Regular audits of user permissions are advisable.

Answer 125

Wrong permissions on `~/.ssh` or on key files. Required: `chmod 700 ~/.ssh`, `chmod 600 ~/.ssh/authorized_keys`. ## Footnote Correct permissions are critical for SSH access.

Answer 126

`systemctl status ` for immediate error output. ## Footnote This provides insight into the failure reason.

Answer 127

`journalctl -u -xe`. ## Footnote This is essential for diagnosing service issues.

Answer 128

The script lacks a valid shebang or uses Windows line endings (CRLF). ## Footnote Ensuring correct script formatting is crucial.

Answer 129

The service file is missing or not reloaded. Run: `sudo systemctl daemon-reload`. ## Footnote This is important for ensuring service availability.

Answer 130

Crash loop due to bad configuration, missing dependencies, or failing health checks. ## Footnote This requires reviewing service configuration and dependencies.

Answer 131

PATH not updated; may need to restart terminal or check `/usr/local/bin`. ## Footnote This is important for ensuring command availability.

Answer 132

Outdated package index. Fix: `sudo apt update`. ## Footnote Keeping the package index updated is essential for package management.

Answer 133

The repository is missing or disabled; needs to be added to `/etc/apt/sources.list`. ## Footnote Ensuring repository availability is crucial for package installation.

Answer 134

The `/var` partition specifically is full; apt stores packages in `/var/cache/apt/`. ## Footnote Monitoring partition usage is vital for package management.

Answer 135

Kernel remounted the filesystem read‑only due to corruption or disk errors. ## Footnote This requires immediate attention to filesystem health.

Answer 136

`mount | grep `. ## Footnote This helps in diagnosing filesystem issues.

Answer 137

Incorrect entries in `/etc/fstab`, wrong UUID, or missing device. ## Footnote Proper configuration of `/etc/fstab` is essential for boot processes.

Answer 138

The process hit its file descriptor limit. Increase with `ulimit -n`. ## Footnote This is important for managing resource limits.

Answer 139

A process is using that mount. Check with `lsof +D `. ## Footnote Identifying active processes is crucial for unmounting.

Answer 140

The filesystem is out of inodes — too many small files. ## Footnote Monitoring inode usage is essential for filesystem health.

Answer 141

DNS lookup delays in SSH session; fix by editing `/etc/hosts`. ## Footnote This can significantly improve command response times.

Answer 142

Cron runs with a limited PATH; absolute paths must be used. ## Footnote This is important for ensuring scripts run as expected.

Answer 143

The script is currently being executed; Linux locks it until done. ## Footnote This is a normal behavior in Linux to prevent execution issues.

2.0 Operating Systems & Linux Basics Flashcards

(167 cards)