Command & Config Cheat Sheet 🚀

A handy collection of commands and config snippets I frequently use. Because who has time to remember them all? 🤷‍♂️

List:

• UFW commands
• Port and Connection check
• Add Swap Space on Ubuntu 18.04
• PHP
• MySQL Commands
• Nginx
• Files
• Docker
• GPG Encrypting and decrypting file
• HTTPS/SSL
• Git
• ETC
• System
• Useful Gist

UFW commands

Description	command
Allow specific Port	ufw allow 6379
Allow Specific IP	ufw allow from 203.0.113.4
Allow Specific Port to specific IP	ufw allow from 203.0.113.4 to any port 6379
Allow Specific Port Ranges udp	ufw allow 5000:5009/udp
Allow Specific Port Ranges tcp	ufw allow 5000:5009/tcp
Allow Specific Port Ranges to to IP tcp	ufw allow from 203.0.113.4 to any port 5000:5009 proto tcp
Deny all connections from Specific IP	ufw deny from 203.0.113.4
------------	--------------
Deny all outgoing traffic	ufw default deny outgoing
Allow all outgoing traffic	ufw default allow outgoing
Deny all incoming traffic	ufw default deny incoming
Allow all incoming traffic	ufw default allow incoming

Port and Connection check

IP count on port 80 & 443:

netstat -anp | grep ':80\|:443' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n | wc -l

Connection count on port 80 & 443:

netstat -an | grep ':80\|:443' | wc -l

Find Out What Is Using TCP Ports

netstat -tulpn

Checking port with netcat

nc -vz -w 5 142.250.203.110 443

Find a website’s DNS address

dig ns saderi.com OR dig +short ns saderi.com

Check SMTP connection in command line

First install swaks (Swiss Army Knife for SMTP)

swaks --to YOUR_SMTP_SERVER \
      --from from@YOUR_SMTP_SERVER \
      --server YOUR_SMTP_SERVER:PORT \
      --auth LOGIN \
      --auth-user SMTP_USERNAME \
      --auth-password "SMTP_PASSWORD" \
      --tls-optional

The --tls-optional flag is used to allow the connection to proceed even if TLS fails

Add Swap Space on Ubuntu 18.04

fallocate -l 4G /swapfile
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile
cp /etc/fstab /etc/fstab.bak
echo '/swapfile none swap sw 0 0' | tee -a /etc/fstab

PHP

Find all php files and syntax check

find . -iname "*.php" -print0 | xargs -0 -n1 php -l

Syntax check for laravel project

find . \( -path ./vendor -o -path ./node_modules -o -path ./storage -o -path ./.git \) -prune -o -name '*.php' -print0 | xargs -0 -n1 php -l > /dev/null

MySQL Commands

Size of specified database in MB

SELECT table_schema ,
    ROUND(SUM(data_length + index_length) / 1024 / 1024, 1) "DB Size in MB" 
    FROM information_schema.tables  WHERE table_schema='DB_NAME'
    GROUP BY table_schema ;

Nginx

Certbot for proxy-pass

server {
    server_name YOUR_DOMAIN.COM;
    listen 80;

    location ~ /.well-known/acme-challenge/ {
        allow all;
        root /var/www/html;
    }

    location / {
        client_max_body_size 15M;
        proxy_pass http://127.0.0.1:8000; # YOUR Service
        proxy_http_version 1.1;
        proxy_set_header Upgrade         $http_upgrade;
        proxy_set_header Connection      'upgrade';
        proxy_set_header X-Real-Ip       $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host            $host;
        proxy_cache_bypass $http_upgrade;
    }
}

Files

Delete files older than 5 days

find /tmp/* -type f -mtime +5 -exec rm -f {} +

Delete files older than 5 minutes

find /tmp/* -type f -mmin +5 -exec rm -f {} +

chmod all folder to 755

find /var/www/html -type d -print0 | xargs -0 chmod 755

chmod all file to 644

find /var/www/html -type f -print0 | xargs -0 chmod 644

Single line loop

for i in {a..z}; do YOUR_COMMAND; done

or

for((i=1;i<=100;i+=5)); do echo "Hi ${i}"; done

Change multiple files extensions in recursive folders

find . -name '*.xtA' -exec bash -c 'mv "$0" "${0%.xtA}.xtB"' "{}" \;

Get files/folders size, include hidden files/folders with du command [ source ]

du -sch .[!.]* * |sort -h

Docker

Copy Docker images from one host to another without using a repository

Save the Docker image as a tar file:

docker save -o TAR_FILE_PATH_AND_NAME IMAGE_NAME:TAG

Copy your image to a new server and load the image into Docker:

docker load -i TAR_FILE_PATH_AND_NAME

Re-balance swarm tasks when new nodes join or after recovery of a node

for service in $(docker service ls -q); do docker service update --force $service; done

GPG Encrypting and decrypting file

Generate a new keypair

gpg --full-generate-key

Export the keypair to a file

gpg --export -a "EMAIL OR KEY_NAME" > public.key

Import public key to your keystore

gpg --import someone_public.key

Encrypt EXAMPLE.gz File

gpg --output ENCRYPTED_EXAMPLE.gpg --recipient "EMAIL OR KEY_NAME" --armor --always-trust --encrypt EXAMPLE.gz

Decrypt EXAMPLE.gz File

gpg --output EXAMPLE.gz --recipient "EMAIL OR KEY_NAME" --decrypt ENCRYPTED_EXAMPLE.gpg

HTTPS/SSL

Check SSL KEY and CRT files relation

If the output of both commands is equal, privet key and ssl certificate are related

openssl x509 -noout -modulus -in domain.crt.pem | openssl md5
openssl rsa -noout -modulus -in domain.privet_key.pem | openssl md5

Extracting the certificate and keys from a .pfx file

The .pfx file, which is in a PKCS#12 format, contains the SSL certificate (public keys) and the corresponding private keys

Extract the private key (this key is encrypted)

openssl pkcs12 -in [YOUR_FILE.pfx] -nocerts -out encrypted_private_key.pem

Extract the certificate

openssl pkcs12 -in [YOUR_FILE.pfx] -clcerts -nokeys -out certificate.pem

Decrypt the encrypted private key

openssl rsa -in encrypted_private_key.pem -out decrypted_private_key.pem

Get expiration date of a SSL certificate

cat domain.crt.pem | openssl x509 -noout -dates

or

openssl s_client -servername DOMAIN_NAME -connect DOMAIN_NAME:443 2>/dev/null | openssl x509 -noout -dates

Git

Change latest commit author

git commit --amend --author="YOURNAME <YOUR_EMAIL@GIT_SERVER.COM>" --no-edit

Git ignore file mode (chmod)

git config core.fileMode false

Empty commit

git commit --allow-empty -m "Empty Commit"

ETC

Convert cuttent folder subtitles to UTF8 Encoding

for FILENAME in ./*.srt; do iconv -f cp1256 -t UTF-8 "${FILENAME}" -o "${FILENAME}"; done;

Merge / convert multiple PDF files into one PDF [ source ]

pdftk file1.pdf file2.pdf cat output output.pdf

Convert larg video to smaller video

ffmpeg -i inputfile.mp4 -acodec aac -s 1366x768 inputfile_smaller.mp4

Breaking large file into small pieces and reassemble them

split

$ split --verbose -b500M large_2.4GB_file.tar small_600MB_files.tar.
creating file 'small_600MB_files.tar.aa'
creating file 'small_600MB_files.tar.ab'
creating file 'small_600MB_files.tar.ac'
creating file 'small_600MB_files.tar.ad'
creating file 'small_600MB_files.tar.ae'

reassemble

cat small_600MB_files.tar.a? > large_2.4GB_file.tar

System

Allow non-root user run sudo command without password

To allow deploy user to use sudo systemctl command for nginx service without password add following lines to end of /etc/sudoers file

%deploy ALL= NOPASSWD: /usr/bin/systemctl restart nginx.service
%deploy ALL= NOPASSWD: /usr/bin/systemctl stop nginx.service
%deploy ALL= NOPASSWD: /usr/bin/systemctl start nginx.service 
%deploy ALL= NOPASSWD: /usr/bin/systemctl status nginx.service

Journal Filtering by Time [ source ]

journalctl --since "2023-06-16 08:55" --until "2023-06-16 09:15"

Clean up journalctl logs

Retain only the past two days:

journalctl --vacuum-time=2d

Retain only the past 500 MB:

journalctl --vacuum-size=500M

Useful Gist

• Install make, vim, git and Docker