Linux

Hard Disk Drive vs Solid State Disk

Hard disks have a motor and moving parts, while solid state disks do not and provide faster access to stored data.

CentOS

A Linux distribution that allows Red Hat Enterprise Linux users to apply their knowledge for a hobby project.

Reverse DNS

The process of assigning hostnames to IP addresses.

SATA Bus

Type of bus that connects hard disk drives with the motherboard.

DNS Resolution Command

The 'host' command is used to resolve a DNS name to an IP address.

Top Command

Displays running processes ordered by CPU or RAM consumption.

Free Command

Displays memory usage information including total, used, and available memory.

dmesg

Displays the content of the Linux kernel’s ring buffer and may not show older information.

Last Command Output

Shows the last login information and session details.

File Ownership

Each file is owned by exactly one user and one group.

UID for Root User

0 is the UID of the root user.

chmod 654

Modifies permissions, setting them to -rw-r-xr-- for a regular file.

Tar Compression Options

-z and -j handle compression in tar commands.

/tmp Permissions

Set to rwxrwxrwt, allowing all users to write but restricting deletion.

/etc/passwd Information

Stores the username, numerical user ID, and user’s default shell.

Add User with Home Directory

The command 'useradd -m tux' creates a user with a home directory.

Create Archive with Tar

Use 'tar -cf work.tar ./work/' to create an archive.

Execute Shell Script

Use 'bash test.sh' or './test.sh' to execute a valid shell script.

Exit less Command

Press 'q' to exit the less command.

Start Loop in Shell Script

The keyword 'for' is used to begin a loop in a shell script.

Find File Command

The 'find /home -name foo.txt' command is used to search for files.

Output of Shell Script Loop

The script outputs a.txt b.txt when using for file in *.txt.

Execute Bit for Script

The execute bit should be set in permissions to execute a shell script.

Sort Output Command

Use 'export-logs | sort' to sort the output of the export-logs command.

Linux Distribution Definition

A bundling of the Linux kernel, system utilities, and other software.

OS on Raspberry Pi

Stored on a removable SD card inserted into the Raspberry Pi.

Vector Graphics Editor

Inkscape is a graphical editor for vector graphics.

Red Hat Package Manager

rpm is the package management tool used in Red Hat-based systems.

Root Privilege Indicator

The '#' character in the shell prompt indicates root privileges.

Public Cloud Services

Include Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

Free Software License

Defines the conditions for modifying and distributing licensed software.

Web Browser Cookies Risks

Support identification and tracking of users, which is a security risk.

Remove Empty Directory Command

Use 'rmdir Downloads' or 'rm -r Downloads' to remove an empty directory.

Recursive Directory Listing

Includes the content of sub-directories.

Commands for ls Usage

Use 'man ls' or 'info ls' to get information on the ls command.

Documentation Directory

/usr/share/doc/ contains documentation and example configuration files.

Display Directory Content

'ls ../Documents/' displays the content of /home/user/Documents/.

Add to PATH Variable

Use 'export PATH=/new/dir:$PATH' to add a directory to the PATH.

Copy Text Files Command

'cp *.txt /tmp/' copies all .txt files to the /tmp/ directory.

Split Command Across Lines

Use '\' to split a command across multiple lines.

DNS Record Types for IP

AAAA and A records hold an IP address.

Valid Process ID

21398 is a valid process ID on Linux.

Automatic IP Configuration Protocol

DHCP is the protocol used for automatic IP address configuration.

Hard Disk Partition Representation

/dev/sda2 represents a hard disk partition.

Linux Hardware Drivers

Drivers are either compiled into the Linux kernel or loaded as kernel modules.

/proc/ Directory Contents

Contains one directory per running process.

Long-Term Server Requirement

Ubuntu Linux LTS and Red Hat Enterprise Linux meet the requirements for long-term support.

Writable Directory Mount Requirement

/var must be mounted with read and write access.

Change File Owner Command

'chown tux doku.odt' changes the ownership of a file.

File after Owner Deleted

The UID of the former owner is shown, and ownership remains unchanged.

/etc/skel Functions

Contains default configuration files for new users and is copied at account creation.

Links in Linux File System

A symbolic link can point to a file on another file system.

Information Sources for User IDs

/etc/passwd and /etc/group are sources for user information.

passwd Command Functions

Change a user's password and lock a user account.

su Command Functionality

Runs a shell or command as another user.

Recursive Listing Parameter for ls

'ls -R' prints a recursive listing of a directory's content.

Usage Information for Commands

Displayed by running the command with the -h or --help option.

Current Directory Path Command

'pwd' shows the absolute path to the current working directory.

Display Text File Content Command

'cat Texts\ 2.txt' or 'cat 'Texts 2.txt'' displays the file content.

Display File Names Only Command

'ls -a' shows file names only without additional information.

Purpose of PATH Variable

Allows execution of commands without knowing the executable's location.

Set Variable Command

'USERNAME=bob' sets the variable USERNAME to the value bob.

Manual Pages Command

'man' displays manual pages.

Copy Directory Contents Command

Use 'cp -r /etc/* /root' to copy contents including subdirectories.

Sort File Lines Command

'sort data.csv' sorts the lines of the file alphabetically.

For Loop Structure in Shell Script

for file in *.txt do echo $i done shows the loop structure.

Regular Expression Operator

The '?' operator matches the preceding character zero or one time.

Export Variable for Script

'export MYVAR=value' makes MYVAR available for script execution.

Return Value of Shell Script

The return value of a successful shell script execution is 0.

Create ZIP Archive Command

Use 'zip poems.zip *.txt' to create a ZIP archive.

Typical Shell Script Features

Starts with #! and has the executable permission bit set.

Extract Compressed Archive Command

Use 'tar -xzf file1.tar.gz' to extract contents of a tar.gz file.

Grep Command for Case Insensitive Search

Use 'grep -i linux operating-systems.txt' to find lines containing the term.

True Passwords Statement

Passwords are only stored in hashed form.

Web Server Programs

Apache and NGINX are web server software.

Red Hat Derived Linux Distribution

CentOS is derived from Red Hat Enterprise Linux.

True Statement about Free Software

Free Software may be modified by anyone using it.

Provisioning Linux Instance in Cloud

Pre-prepared images of popular distributions are used for new instances.

Private Browsing Differences

Private windows do not store cookies persistently, do not keep history, and do not send regular cookies.

Preferred Source for Apps in Linux

The distribution's package repository is the preferred source for application installation.