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Cool terminal commands cheatsheet by Ehsan Shirzadi

Terminal commands:

Want to know your public IP?

wget -qO - icanhazip.com

Remove all files but one?

rm -v !("filename")

Base64 Encode

echo string_to_encode | base64

Base64 Decode

echo ZWhzYW5zaDg0Okp1Y2lhbEB4NjQ= | base64 --decode

Remove all files but two?

rm -v !("filename1"|"filename2")

Remove all files but two types?

rm -v !(.zip|.odt)

Rename terminal window echo $'\033]30;NewName\007'

List all files but *conf

ls -I "*conf"

List all dirs

ls -d */

list all files containing my_text ###grep -iRl "my_text" *

get certificate:

certbot certonly -d domain —expand -d www.domain.com

Change timzone for ubuntu

sudo timedatectl set-timezone Asia/Tehran

See listening ports:

ss -tulpn

Echo with a typewriter effect:

apt install pv
echo "You can simulate on-screen typing just like in the movies" | pv -qL 10

Grep lines before and after:

grep -A 5 keyword filename #after
grep -B 5 keyword filename #before
grep -C 5 keyword filename #center

Tunnel network traffic:

sudo sshuttle --dns -vvr root@x.x.x.x 0/0

If encountered with the error fatal: server died with error code 255 run this command instead:

sudo sshuttle --dns -vvr root@x.x.x.x[:443] --exclude x.x.x.x 0/0

Hard disk performance test:

fio --loops=5 --size=1024m --filename=/mnt/nfs/test12.txt --stonewall --ioengine=libaio --direct=1 \
  --name=Seqread --bs=1m --rw=read \
  --name=Seqwrite --bs=1m --rw=write \
  --name=512Kread --bs=512k --rw=randread \
  --name=512Kwrite --bs=512k --rw=randwrite \
  --name=4kQD32read --bs=4k --iodepth=32 --rw=randread \
  --name=4kQD32write --bs=4k --iodepth=32 --rw=randwrite

Problem with apt update?

printf "deb http://archive.debian.org/debian/ jessie main\ndeb-src http://archive.debian.org/debian/ jessie main\ndeb http://security.debian.org jessie/updates main\ndeb-src http://security.debian.org jessie/updates main" > /etc/apt/sources.list

Change system DNS:

vim /etc/systemd/resolved.conf 
systemctl restart systemd-resolved.service

Change system DNS another way:

vim /etc/systemd/resolved.conf 
systemctl restart systemd-resolved

Fix missing VPN client

sudo apt install network-manager-pptp-gnome

Find all sockets on your system:

sudo find / -type s

ls and numerical permissions:

 ls -l | awk '{k=0;for(i=0;i<=8;i++)k+=((substr($1,i+2,1)~/[rwx]/) \
             *2^(8-i));if(k)printf("%0o ",k);print}'

Unset env variables:

unset GNUPLOT_DRIVER_DIR

Check for your public IP:

wget -qO - icanhazip.com

Run a python script as a linux command:

Put a shebang #! /usr/bin/python on top of script Then make in executable:

sudo chmod +x script.py

Put it inside /usr/bin Remove .py so script.py will be script Run!

Remove a virtual network interface:

sudo ip link delete interface_name

Find a directory:

find / -name DIRNAME -type d

Check traffics on the port:

tcpdump -i <interface-name> port <port-number>

Check traffics on the port a few exclusions:

tcpdump -i <interface-name> port <port-number> -n port not 22 and not arp and port not 53

Check traffics on the port 443:

tcpdump -i ens3 port 443

Color specific word in output (| is necessary):

command | grep --color -P "word|"

Add user to sudoers:

Edit this file: /etc/sudoers and add this line to the end of file:

username  ALL=(ALL) NOPASSWD:ALL

Set default ssh port for specific host: ~/.ssh/config

Host git.greenrnd.com
    User git
    Hostname git.greenrnd.com
    Port 2580

How much disk is used by journalctl

journalctl --disk-usage

How to increase your swap size?

SWAP_PATH=/root/swap.swp
swapoff -a
dd if=/dev/zero of=$SWAP_PATH bs=1M count=16384 #count=1024*16=16GBi
chmod 600 $SWAP_PATH
mkswap $SWAP_PATH
swapon $SWAP_PATH

Finally, edit /etc/fstab and comment current swap file:

/swapfile                                 none            swap    sw              0       0

and add this line:

/root/swap.swp             swap        swap         defaults                0       0

How to see SSL certificate details:

echo | openssl s_client -showcerts -servername gnupg.org -connect gnupg.org:443 2>/dev/null | openssl x509 -inform pem -noout -text

List all partitions

sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL

Filter output by multiple keywords:

ls | egrep "(kw1|kw2)"

See list of connections to current server:

rm -rf /home/ubuntu/.configrc/*

Change ssh port from 22 to 2580, remove -i if you want changed not applied

sed -i 's/#Port 22/Port 2580/g' /etc/ssh/ssh_config

Added iranserver repos for Ubuntu 20.04 Focal Fossa

echo "deb https://mirror.iranserver.com/ubuntu focal main restricted universe multiverse" | tee -a /etc/apt/sources.list
echo "deb https://mirror.iranserver.com/ubuntu focal-updates main restricted universe multiverse" | tee -a /etc/apt/sources.list
echo "deb https://mirror.iranserver.com/ubuntu focal-security main restricted universe multiverse" | tee -a /etc/apt/sources.list

Added arvancloud repos for alpine:3.16

echo http://mirror.arvancloud.com/alpine/v3.16/main > /etc/apk/repositories

List directories with size

du -sh *

Replace with env using sed

sed 's/xxx/'$PWD'/'

Define alias with parameter:

alias xx='function ssh_ip() { ssh -p2510 ubuntu@"$1"; }; ssh_ip'