Linux Commands

ls

list directory contents

cd

change directory

pwd

print working directory

cp

copy files and directories

mv

move or rename files and directories

rm

remove files or directories

mkdir

make directories

rmdir

remove empty directories

touch

change file timestamps or create empty files

find

search for files in a directory hierarchy

locate

find files by name

tree

display directories in a tree like format

chmod

change file permissions

chown

change file owner and group

chgrp

change group ownership

stat

display file or file system status

cat

concatenate and display file content

tac

concatenate and display file content in reverse

more

view file content interactively (page by page)

less

view file content interactively (scrollable)

head

output the first part of a file

tail

output the last part of a file

nano

text editor in terminal

vim or vi

advanced text editor in terminal

emacs

text editor in terminal

grep

search text using patterns

sed

stream editor for filtering and transforming text

awk

pattern scanning and processing language

cut

remove sections from each line of files

sort

sort lines of text files

uniq

report or omit repeated lines

ps

report a snapshot of current processes

top

display linux tasks

htop

interactive process viewer (advanced top)

kill

send a terminate signal to a process

killall

terminate process by name

bg

resume a suspended background job

fg

bring a job to the foreground

jobs

list active jobs

nice

run a program with modified scheduling priority

renice

alter priority of running processes

uptime

show how long the system is up and running

time

measure program running time

df

report file system disk space usage

du

estimate file space usage

fdisk

partition table manipulator

lsblk

list information about block devices

mount

mount a file system

umount

unmount a file system

parted

partition table manipulator

mkfs

create a file system

fsck

file system consistency check and repair

blkid

locate/print block device attributes

ifconfig

configure network interfaces

ip

show/manipulate routing, devices and tunnels

ping

send ICMP echo requests to network host

netstat

network statistics

ss

socket statistics

traceroute

trace the route packets take to a network host

nslookup

query internet name servers interactively

dig

DNS lookup utility

wget

non-interactive downloader

curl

transfer data with URLs

scp

secure copy files between hosts

ssh

secure shell for remote login

ftp

file transfer protocol client

useradd

add a user

usermod

modify a user

userdel

delete a user

groupadd

add a group

groupdel

delete a group

passwd

modify the user password

chage

change password expiry information

whoami

print the current logged in user

who

show who is logged in

w

show who is logged in and what they are doing

id

display the user and group id

groups

show the user's groups

uname

print system information

hostname

show or set the system's hostname

uptime

how long the system has been running

dmesg

boot and system messages

free

display memory usage

top

display linux tasks

vmstat

report virtual memory statistics

lscpu

display information about the CPU architecture

lsusb

list USB devices

lspci

list PCI devices

lshw

list hardware configuration

tar

archive files
tar -czf test.tar.gz /directory/path/ → compress files using gzip
tar -xzf test.tar.gz → extract gzipped tarball
tar -cf test.tar → /directory/path → create a tarball
tar -xf test.tar → extract tarball

zip

package and compress files into a ZIP archive

unzip

extract files from a ZIP archive

gzip

compress files using the gzip algorithm

gunzip

decompress files compressed with gzip

bzip2

compress files using the bzip2 algorithm

bunzip2

decompress files compressed with bzip2

xz

compress files using the xz algorithm

unxz

decompress files compressed with xz

apt-get

APT package handling utility
apt-get install packagename → install a package
apt-get update → update package list
apt-get upgrade → upgrade installed packages
apt-get remove packagename → remove a package

apt-cache

query APT cache
apt-cache search packagename → search for a package
apt-cache show packagename → show package details

yum

package manager for RPM based systems
yum install packagename → install a package
yum update → update installed package
yum remove packagename → remove a package

dnf

next generation package manager (CentOS 8+, Fedora)
dnf install packagename → install a package
dnf update → update installed packages
dnf remove packagename → remove a package

rpm

RPM package manager
rpm -i packagename.rpm → install an RPM package
rpm -e packagename → remove an RPM package

dpkg

Debian package manager
dpkg -i packagename.deb → install a Debian package
dpkg -r packagename → remove a Debian package

systemctl

control the systemd system and service manager
systemctl start servicename → start a service
systemctl stop servicename → stop a service
systemctl restart servicename → restart a service
systemctl enable servicename → enable a service to start on boot
systemctl disable servicename → disable a service from starting on boot
systemctl status servicename → check service status

service

older service management command (used in non systemd systems)
service servicename start → start a service
service servicename stop → stop a service
service servicename restart → restart a service
service servicename status → check service status

cron

daemon for running scheduled commands
crontab -e → edit cron jobs for the current user
crontab -l → list the current user's cron jobs
crontab -r → remove the current user's cron jobs

at

run commands at a specified time
at 06:00 → schedule a command to run at 6:00 o'clock

batch

run commands when the system load is low

sleep

delay for a specified time
sleep 6s → sleep for 6 seconds

chmod

change file permissions

chown

change file owner and group

chgrp

change the group ownership of a file

umask

set default permissions for new files

setfacl

set file access control lists (ACL)

getfacl

get file access control lists

sudo

execute a command as another user (usually root)

visudo

edit the sudoers file safely

passwd

change a user's password

sudoers

manage sudo access for users

gpasswd

administer group password

ss

display socket statistics (for secure network connections)

rsync

remote file and directory synchronization
rsync -avz source destination → synchronize files
rsync -avz -e ssh source user@remote:/destination/ → sync over SSH

cpio

copy files to and from archives

dd

low-level copying and backup of entire filesystems
dd if=/dev/sda of=/path/backup.img → backup a disk or partition
dd if=/path/backup.img of=/dev/sda → restore a disk or partition

dmesg

print the kernel ring buffer messages
system boot and hardware related messages

journalctl

query and view logs from systemd's jourmal

strace

trace system calls and signals
strace commandname → trace a command's system call

lsof

list open files
lsof files → show processes using a specific file

vmstat

report virtual memory statistics

iostat

report CPU and I/O statistics

mpstat

report CPU usage statistics

pidstat

report statistics by process

free

display memory usage

uptime

how long the system has been running

watch

execute a program periodically - showing output
watch -n 1 free → watch memory usage every second

lshw

list hardware configuration

htop

interactive process viewer

netstat

network statistics (replaced by ss)

ss

show socket statistics

ifconfig

configure network interfaces (replaced by ip)

ip

a more modern alternative for managing network interfaces and routing
ip addr → show ip addresses
ip link → show or manipulate network interfaces
ip route → show or manipulate routing tables

ss

show socket statistics

nmap

network exploration tool

telnet

user interface to the telnet protocol

nc

network utility for reading and writing from network connections
netcat
nc -l -p 1234 → listen on port 1234
nc host port → connect to a host and port

iptables

administration tool for IPv4 packet filtering and NAT

firewalld

frontend for managing firewall rules (Fedora/CentOS)

ufw

uncomplicated firewall
ufw enable → enable firewall
ufw allow port → allow traffic on a specific port

tcpdump

command line packet analyzer

curl

transfer data from or to a server using various protocols

wget

download files from the web

scp

secure copy over SSH
scp test.txt user@remotemachine:/path → copy file to remote machine

rsync

remote file and directory synchronization
rsync -avz /path/ remotemachine:/path → sync directories between 2 machines

grep

search for patterns within files
grep 'pattern' file.txt → search for a pattern in a file
grep -r 'pattern' /dirname/ → recursively search for a pattern

sed

stream editor for filtering and transforming text
sed 's/old/ne/g' file.txt → replace old by new globally

awk

a powerful text processing language
awk '{print $1} file.txt → print the first column of each line in a file

cut

remove sections from each line of a file
cut -d ':' -f 1 /etc/passwd → print the first field of each line delimited by ":"

sort

sort lines of text files
sort file.txt → sort file content in ascending order

uniq

report or omit repeated lines in a file
sort file.txt | uniq → sort an remove duplicate lines

tee

read from standard input and write to standard output and files
echo "text" | tee file.txt → write to file and show output on screen

tr

translate or delete characters
echo "hello" | tr 'a-z' 'A-Z' → convert lowercase to upercase letters

paste

merge lines of files
paste file1.txt file2.txt → combine lines of file1 and file2 side by side

wc

word, line, character and or byte count
wc -l file.txt → count lines in a file
wc -w file.txt → count words in a file

shutdown

shut down a system
shutdown -h now → immediately shut down the system
shutdown -r now → immediately reboot the system
shutdown -h +10 → shut down after 10 minutes

reboot

reboot the system

halt

halt the system immediately

poweroff

power off the system

init

change the runlevel (old-style system manager)
init 0 → shutdown
init 6 → reboot

mount

mount a file system
mount /dev/sda1 /mnt → mount partition to a directory

umount

umount a file system
umount /mnt → unmount the file system mounted at /mnt

fstab

file system table
configuration file for mounting file systems

blkid

display block device attributes

fsck

check and repair a file system
fsck /dev/sda1 → check and repair /dev/sda1

chmod

change file permissions
chmod 755 file.txt → give read write and execute permissions to owner
and read/execute permissions to others

chown

change file owner and group
chown user:group file.txt → change owner and group of a file

chgrp

change group ownership of a file
chgrp group file.txt → change the group of a file

umask

set default permissions for new files
umask 022 → set default permissions for newly created files to 755

setfack

set access control lists (ACL) for file permissions

getfacl

get access control lists (ACL) for file permissions

docker

docker command line (CLI) for managing containers

docker run image

run a container from an image

docker ps

list running containers

docker ps -a

list all containers including stopped ones

docker build -t imagename .

build an image from a dockerfile

docker exec -it container_id bash

start an interactive bash shell inside a running container

docker stop container_id

stop a container

docker rm container_id

remove a container

docker logs container_id

view logs of a container

dock images

list available images

docker rmi imagename

remove an image

docker network ls

list docker networks

docker-compose

manage multi-container docker applications

docker-compose up

start up a multi-container environment

docker compose down

stop and remove containers created by docker-compose

docker-compose logs

view logs from containers managed by docker-compose

kubectl

command line tool for interacting with Kubernetes clusters

kubectl get pods

list pods in the current namespace

kubectl get nodes

list nodes in the cluster

kubectl get services

list services in the cluster

kubectl apply -f file.yaml

apply configuration from a file

kubectl create -f file.yaml

create a resource from a file

kubectl delete -f file.yaml

delete a ressource defined in a file

kubectl exec -it podname --bash

execute a command inside a pod (ex. open a shell)

kubectl logs podname

view the logs of a pod

kubectl describe pod podname

get detailed information about a pod

kubectl scale deployment deploymentname --replicas=number

scale a deployment to the desired number of replicas

kubectl rollout restart deployment deploymentname

restart a deployment

kubectl port-forward pod podname localport:remoteport

forward a port from a pod to localhost

helm

Kubernetes package manager for deploying applications

helm install releasename chartname

install a helm chart

helm upgrade releasename chartname

upgrade a helm release

helm list

list all helm releases

helm delete releasename

delete a helm release

helm search chartname

search for a helm chart

ansible

automation tool for configuration management

ansible all -m ping

ping all hosts defined in the inventory

ansible-playbook playbook.yml

run an ansible playbook

ansible -m command -a 'command' host

run a single command on a target host

ansible-playbook --check playbook.yml

dry run a playbook to see what would change

ansible-playbook --limit host playbook.yml

run a playbook on a specific host or group

ansible-playbook --extra-vars "key=value"

pass extra variables to a playbook

terraform

infrastructure as code tool for provisioning and managing cloud ressources

terraform init

initialize a working directory for terraform configuration

terraform plan

show an execution plan (what changes would be made)

terraform apply

apply the changes described in a terraform configuration

terraform destroy

destroy infrastructure created by terraform

terraform validate

validate the configuration files

terraform show

show the current state of the infrastructure

puppet

configuration management tool

puppet apply manifest.pp

apply a puppet manifest locally

puppet agent ---test

test the puppet agent

puppet resource

show the current state of resources
(files, services, etc.)

jenkins

continous integration tool

java -jar jenkins.war

start jenkins from a war file
access jenkins trough http://localhost:8080 by default

.gitlab-ci.yml

configuration file for GitLab CI/CD pipelines

gitlab-runner register

register a new runner with GitLab

gitlab-runner run

run the Gitlab Runner to process jobs

Info

GitHub Actions uses YAML configuration files
typically located in .github/workflows/

actions/checkout@v2

checkout the repository code in your CI pipeline

actions/setup-node@v2

setup Node.JS for use in a pipeline

docker/setup-buildx-action@v1

set up docker buildx for building multi platform images

aws

command line tool for managing AWS services

aws configure

configure AWS CLI with your credentials

aws s3 cp file.txt s3://bucketname/

copy a file to an S3 bucket

aws ec2 describe-instances

descripe EC2 instances

aws ec2 start-instances --instance-ids id

start an EC2 instance

aws ec2 stop-instances --instance-ids id

stop an EC2 instance

aws s3 sync

sync directories with an S3 bucket

az

command line tool for managing Azure services

az login

log in to your Azure account

az vm list

list all virtual machines

az vm start --name vmname --resource-group resourcegroup

start an Azure VM

az storage blob upload

upload files to an Azure blob storage

az group create

create a new resource group in Azure AD

gcloud

command line tool for Google cloud platform

gcloud auth login

log in to Google cloud

gcloud compute instances list

list compute instances

gcloud compute instances stop instancename

stop a Google cloud VM instance

gcloud ap browse

open the current Google app engine application in a browser

prometheus

open source system monitoring and alerting toolkit
start prometheus server (usually as a background service)

prometheus --config.file=configfile

start prometheus with a specific config file

grafana-cli

command line interface for managing Grafana plugins

grafana-cli plugins install pluginname

install a plugin in Grafana

elasticsearch

search engine for logging and data analytics

curl -XGET 'localhost:9200/_cluster/health?pretty'

get cluster health status

logstash

server side data processing pipeline

logstash -f configfile

run logstash with the specified configuration file

kibana

web interface for visualizing Elasticsearch data
Kibana is generally access through web on http://localhost:5601