Unix File Management Basics

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Questions and Answers

What command is used to create an empty file?

touch filename.txt

Which command can create a file and write a line of text to it?

echo "Hello, World!" > filename.txt

What command is used to display the content of a file?

cat filename.txt

Which command would you use to append text to an existing file?

echo "Additional text" >> filename.txt Signup and view all the answers

The command `mkdir` is used to create a _____.

directory Signup and view all the answers

The `rmdir` command can remove a non-empty directory.

False Signup and view all the answers

What command is used to remove a directory and its contents recursively?

rm -r directory_name Signup and view all the answers

What does the `chmod` command do?

It changes file and directory permissions. Signup and view all the answers

What permission corresponds to read-only access for others?

r-- Signup and view all the answers

What command would you use to add a new user to the system?

sudo useradd username Signup and view all the answers

Which file contains basic information about all user accounts?

/etc/passwd Signup and view all the answers

What is the purpose of the `tar` command?

To create, extract, or manage tar archive files. Signup and view all the answers

What does the 'grep' command do?

Searches text using patterns. Signup and view all the answers

A ______ links to another file by storing the path to it.

soft link Signup and view all the answers

What is a key characteristic of hard links?

They share the same inode as the original file. Signup and view all the answers

What command would you use to view the status of a service?

systemctl status servicename Signup and view all the answers

What is the primary purpose of virtualization?

To create multiple virtual machines on a single physical machine. Signup and view all the answers

What is the loopback interface used for?

Internal testing and communication within the host Signup and view all the answers

What is the loopback IP address?

127.0.0.1 Signup and view all the answers

What does LAN stand for?

Local Area Network Signup and view all the answers

What does WAN stand for?

Wide Area Network Signup and view all the answers

What is the function of a Network Interface Card (NIC)?

Connects a computer to a network Signup and view all the answers

At which layer of the OSI model do switches operate?

Data link layer (Layer 2) Signup and view all the answers

At which layer of the OSI model do routers operate?

Network layer (Layer 3) Signup and view all the answers

What does NAT stand for and what is its purpose?

Network Address Translation; it translates private IP addresses to a public IP address. Signup and view all the answers

What is the purpose of a subnet mask?

To divide an IP address into network and host portions Signup and view all the answers

What is a static IP address?

A fixed, unchanging IP address manually set for a device Signup and view all the answers

What is a dynamic IP address?

An IP address assigned automatically by a DHCP server that can change Signup and view all the answers

What is the configuration file for network interfaces in Debian/Ubuntu?

/etc/network/interfaces Signup and view all the answers

What command is used to obtain an IP address from a DHCP server?

dhclient Signup and view all the answers

What does DHCP stand for?

Dynamic Host Configuration Protocol Signup and view all the answers

What does DNS stand for?

Domain Name System Signup and view all the answers

What is the primary function of a firewall?

To configure IP packet filter rules for a system Signup and view all the answers

What is a VPN?

Virtual Private Network Signup and view all the answers

The IP address format of IPv4 consists of _______ bits.

32 Signup and view all the answers

A unique hardware address used within LANs is known as a _______.

MAC Address Signup and view all the answers

Which command can be used to show details of a specific connection?

nmcli con show Signup and view all the answers

Study Notes

File Management in Unix-like Systems

Use touch filename.txt to create an empty file.
echo "Hello, World!" > filename.txt creates a file and writes content.
cat > filename.txt allows creation and input of text to a file.
Edit files with vi filename.txt for a powerful text editor.
Append text to files using echo "Additional text" >> filename.txt.
Merge file content with cat anotherfile.txt >> filename.txt.

Reading Files

Display file content using cat filename.txt.
Use more filename.txt and less filename.txt for paginated reading.
View the beginning of files with head filename.txt.
Check the end of files using tail filename.txt.

Directory Management

Create a directory with mkdir directory_name.
Create nested directories using mkdir -p parent_directory/child_directory.
Remove empty directories with rmdir directory_name.
Use rm -r directory_name for recursive directory removal.
Force deletion with rm -rf directory_name.

File Operations

Copy files with cp source_file destination_file.
Copy multiple files into a directory using cp file1 file2 destination_directory/.
Recursively copy directories using cp -r source_directory destination_directory.
Move or rename files with mv source_file destination_directory/ or mv old_filename new_filename.

File and Directory Permissions

Permissions display as -rwxr-xr--, indicating file type and permissions for owner, group, and others.
r = read, w = write, x = execute.
Change permissions using chmod with symbolic (+, -, =) and numeric methods (e.g., chmod 755 filename).
Set default file permissions based on umask, which subtracts from default values (666 for files, 777 for directories).

User Management

Add a user with sudo useradd username and set password using sudo passwd username.
Use sudo usermod -aG groupname username for additional group permissions.
Remove a user with sudo userdel username or sudo userdel -r username to delete their home directory.

Log Files

/var/log/syslog records system activity and security events.
/var/log/auth.log contains authentication logs for login attempts and account changes.
/var/log/kern.log logs kernel messages for system diagnostics.

Search and Process Management

Use grep and egrep for text searching; egrep supports extended regex.
Common grep flags include -i (ignore case), -r (recursive), -c (count lines), and context options (-A, -B, -C).
Manage processes with systemctl (start, stop, enable, disable services).
Use kill PID or pkill process_name to terminate processes.

Virtualization

Virtualization creates multiple VMs on a single machine for better resource utilization.
Types include Type 1 (bare metal hypervisor) and Type 2 (hosted hypervisor).
VMware ESXi is a Type 1 hypervisor for hardware resource management.
vSphere combines ESXi and vCenter for centralized management of VMs.

Networking Basics

NIC (Network Interface Card) enables device network connectivity.
LAN (Local Area Network) connects devices within a limited area while WAN (Wide Area Network) spans larger geographic areas.
Routers forward packets between networks, while switches connect multiple devices within a LAN.
NAT translates private IP addresses for public internet access and adds security.

IP Addressing

IPv4 uses 32-bit addresses, while IPv6 uses 128 bits for a larger address space.### IPv6 and IP Addressing
IPv6 utilizes 128-bit IP addresses, providing a virtually unlimited address space.
A MAC address is a unique hardware identifier for network interface cards, specifically used within local area networks (LANs).
The subnet mask divides an IP address into network and host portions, helping to identify the network segment.
The default gateway is the router's IP address that forwards local network traffic to other networks, including the internet.

Static vs. Dynamic IP Addresses

Static IP addresses remain fixed and are manually assigned, preferred for devices needing consistent access like servers and printers.
Dynamic IP addresses are automatically assigned by DHCP servers and can change, suitable for devices such as computers and smartphones that connect and disconnect often.

Network Configuration Files

/etc/network/interfaces is used in Debian/Ubuntu for network interface configuration.
/etc/sysconfig/network-scripts/ifcfg-* is for configuring interfaces in Red Hat/CentOS systems.
/etc/nsswitch.conf defines the lookup order for hostname resolution and user information.
/etc/hosts maps hostnames to IP addresses for local name resolution.
/etc/resolv.conf specifies DNS servers for resolving domain names.

Network Configuration Tools

ifconfig is a deprecated tool for network interface configuration.
ip is the modern command used for managing IP addresses and interfaces.
nmcli and nmtui manage NetworkManager through command line and text-based interfaces.
dhclient is a DHCP client tool to receive IP address configurations.

NetworkManager

A Linux system service aimed at simplifying network management, supporting various connection types and adapting to network changes.
Features include dynamic configuration, connection persistence, automatic IP assignment, and an API for user integrations.
It monitors network connectivity and supports security measures such as VPN management.

Network Services

DHCP assigns IP addresses and other network settings automatically to connected devices.
DNS converts user-friendly domain names into IP addresses.
SSH provides a secure protocol for remote machine access.

Routing Concepts

The routing table determines packet paths, modified with route or ip route commands.
Static routing involves manually defined paths, while dynamic routing adjusts automatically through protocols like OSPF and BGP.

Network Diagnostic Tools

ping checks connectivity by sending ICMP echo requests.
traceroute traces paths packets take to a destination.
ip route displays current routing table information.
ethtool configures settings for network interface cards.

Host and VM Information Commands

Use ifconfig, ip addr show, or mcli to find IP addresses.
Network mask/prefix can also be viewed with ifconfig and ip addr show.
Determine the gateway with route -n and netstat -nr.
DNS details can be accessed via nslookup and dig.

Firewalls

iptables is a user-space program to configure packet filter rules for Linux kernel firewalls.
firewalld offers dynamic management of firewall settings via a D-Bus interface.

Virtual Networking

A bridge connects multiple network interfaces at the data link layer.
VLANs create separate broadcast domains on the same physical network.
VPNs establish secure, encrypted connections over potentially insecure networks.

Basic Network Commands

Show all connections: nmcli con show
Get details of a specific connection: nmcli con show <connection_name>
Activate or deactivate a connection: nmcli con up <connection_name>, nmcli con down <connection_name>
Modify or clone connections using nmcli connection modify <connection_name> and nmcli connection clone <source_connection_name>.
Delete a connection: nmcli connection delete <connection_name>.

Creating a New Connection

Create an Ethernet connection with nmcli connection add con-name <name> type ethernet ifname <interface> ipv4.addresses <address> ipv4.dns <dns> ipv4.gateway <gateway> ipv4.method manual connection.autoconnect yes.
Example: nmcli connection add con-name ens171 type ethernet ifname ens192 ipv4.addresses 10.10.60.156/18 ipv4.dns 1.1.1.1 ipv4.gateway 10.10.60.1 ipv4.method manual connection.autoconnect yes.

Packet Management

Handles software packages for installation, updating, and removal.
For Red Hat-based systems, use sudo dnf upgrade to update the package list or yum/dnf commands for installation and removal.
Search installed packages with yum list installed or dnf list installed.

LDAP Overview

LDAP is a protocol for accessing and managing directory services and is essential for centralized user management.
Key concepts include directory services, entries and attributes, distinguished names (DN), schemas, and core operations like Bind, Search, and Compare.

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Description

This quiz covers the essential commands for creating, modifying, and managing files in a Unix-like operating system, such as Linux. Learn how to use commands like touch, echo, and cat effectively to handle files and text. Perfect for beginners looking to enhance their skills in file management.