Operating System

Linux software categories

Server applications; Desktop applications; Tools

what does Linux server applications do

Software that provides information/services to client computers over a network

Linux desktop applications

Software that users interact with directly

Early use of Linux servers

Web servers

Linux email client

Thunderbird

Linux web browsers

mozilla firefox, Chrome

Function of Linux packages

Add, remove, and update software

Package management systems

APT; YUM/DNF

Debian package update command

apt-get update

Digital footprint

Information left online that can be used for advertising or malicious purposes

Cloud computing

Use of remote computing resources over the Internet

Cloud

Data, servers, storage, applications, and resources hosted in remote data centres

Cloud deployment models

Public cloud; Private cloud; Community cloud; Hybrid cloud

Why Linux is suitable for cloud computing

Security; Scalability; Flexibility; Automation

Virtualization

Running multiple guest operating systems on one physical host

Hypervisor

Software that manages and allocates resources to virtual machines

what are 2 Virtualization software

VMware, VirtualBox

Containers

Run applications in isolated containers

Most common Linux shell

Bash

Linux prompt contains

Username; Hostname; Current directory

Function of compression

Reduce file size for storage and transmission

Types of compression

Lossy; Lossless

Most common compression tool

gzip

Decompress gzip command

gunzip

Traditional UNIX archiving tool

tar

Create tar archive

tar -cf file.tar folder/

Create tar.gz archive

tar -czf file.tar.gz folder/

List tar.gz archive

tar -tzf file.tar.gz

Extract tar.gz archive

tar -xzf file.tar.gz

FHS

Filesystem Hierarchy Standard

Commands to view processes

ps; top

/proc

Pseudo filesystem containing process, hardware, and kernel information

/proc/meminfo

Detailed system memory usage information

whats /proc/cmdline

Shows kernel boot parameters passed at startup

/proc/modules

Loaded kernel modules

PID 1

init/systemd process

Parent process

Process that starts another process

Child process

Process started by another process

pstree

Shows parent-child process tree

ps default output

Running processes

top

Real-time process monitoring

free -s 20

Display memory usage every 20 seconds

Logging daemons

syslogd; klogd; journald

Log storage location

/var/log

Commands to view logs

cat; less; journalctl

Command for binary log files

file

/var/log/dmesg

Kernel messages during startup

what does /var/log/messages contain

System messages while running

journalctl

View systemd journal logs

ifconfig

Display and configure network settings

route

Display kernel IP routing table

ping

Check network connectivity and host reachability

ping -c 3 localhost

Send 3 ping requests to localhost

Destination Host Unreachable

No available network path to destination host

netstat

Show network connections, routing table, and open ports

what does ss do

Show socket statistics and active network connections

dig

DNS lookup tool for domain-to-IP mapping and DNS records

what is ssh

Secure remote login and command execution on another machine

file

Identify file type