ss -tulpn

ss -ntp | grep "192.168."

ss -ntp state established

ps -fp <PID>

watch -n 2 ss -tulpn

grep -oE '\b([a-zA-Z0-9-]+\.)+[a-zA-Z]{2,}\b' /var/log/syslog | sort -u

tcpdump -A -s 0 port 80 | grep -oE '\b([a-zA-Z0-9-]+\.)+[a-zA-Z]{2,}\b' | sort -u

ssh -L 8080:internal-server:80 user@gateway

Host myserver
HostName 192.168.1.100
User admin
Port 2222
IdentityFile ~/.ssh/my_key

ssh-copy-id user@server

Host *
ControlMaster auto
ControlPath ~/.ssh/sockets/%r@%h:%p
ControlPersist 600

tar cz folder/ | ssh server "tar xz -C /destination"

ssh server "tail -f /var/log/app.log" | grep -i error

glances

glances -w

glances -s

glances -c IP

glances --browser

nmap -p- -oX baseline.xml 192.168.100.100

nmap -p- -oX current.xml 192.168.100.100

ndiff baseline.xml current.xml

-Nmap 7.80 scan initiated Sat Nov 22 13:32:40 2025 as: nmap -p- -oX baseline.xml 192.168.100.100
+Nmap 7.80 scan initiated Sat Nov 22 13:34:55 2025 as: nmap -p- -oX current.xml 192.168.100.100

192.168.100.100:
-Not shown: 59995 filtered ports, 5538 closed ports
+Not shown: 59994 filtered ports, 5538 closed ports
PORT   STATE SERVICE VERSION
+80/tcp open  http

nohup your_command & disown

folder="~/Documents/photos"
prefix="img_"

cd "$folder"
i=1
for file in *; do
  ext="${file##*.}"
  mv "$file" "${prefix}${i}.${ext}"
  ((i++))
done

IMG1234.jpg, vacation.png, photo_01.jpeg

img_1.jpg, img_2.png, img_3.jpeg

mtr -T --port 443 vpn.example.com

mtr --interval 2 --timeout 10 --report 1.1.1.1

mtr --report --report-cycles 20 example.com

mtr --json 8.8.8.8 > result.json

mtr --aslookup --report example.com

mtr --mpls --report example.com

mtr -n --report 1.1.1.1

mtr -T --port 443 -n --json --report-cycles 15 1.1.1.1

pidof nginx

ls -l /proc/<PID>/fd | grep '(deleted)'

cp /proc/<PID>/fd/<fd_number> ./recovered.log

#!/bin/bash
set -x

src="/etc/hosts"
dst="/tmp/backup"

mkdir -p "$dst"
timestamp=$(date +%Y%m%d_%H%M%S)
cp "$src" "$dst/hosts_$timestamp"

echo "Backup created: $dst/hosts_$timestamp"

# ./backup.sh
+ src=/etc/hosts
+ dst=/tmp/backup
+ mkdir -p /tmp/backup
+ date +%Y%m%d_%H%M%S
+ timestamp=20251007_121330
+ cp /etc/hosts /tmp/backup/hosts_20251007_121330
+ echo 'Backup created: /tmp/backup/hosts_20251007_121330'
Backup created: /tmp/backup/hosts_20251007_121330

stream {
  upstream ssh {
  server 2.2.2.2:22022;
  }

  upstream web {
  server 2.2.2.2:443;
  }

  map $ssl_preread_protocol $upstream {
  "" ssh;
  "TLSv1.2" web;
  default 2.2.2.2:443;
  }

  server {
  listen 1.1.1.1:443;
  proxy_pass $upstream;
  ssl_preread on;
  }

}

http {

$ ssh root@1.1.1.1 -p443
Enter passphrase for key "/home/user/.ssh/id_rsa":

apt install linkchecker -y

linkchecker dir/

linkchecker --check-extern dir/