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Linux

SSH

scp -[r]P <port> <user>@<ip>:<path/to/folder> <path/to/local>

scp -[r]P <port> <source file> <username>@<destination server>:<destination directory>

ssh-keygen -t rsa
ssh-add

ssh-add -l

cat ~/.ssh/id_rsa.pub

# /etc/ssh/ssh_config or ~/.ssh/config
ServerAliveInterval 60

Compress & Extract

# Compress
tar -czvf <file_name.tgz> </path/to/directory>
tar -czvf <file_name.tgz> </path/to/directory>/.  # include hidden files
tar -czvf <file_name.tgz> </path/to/file>

# Extract
tar -xzvf <file_name.tgz>
tar -xzvf <file_name.tgz> -C </path/to/directory>

# Split into multiple files
split --bytes=<split_size: 10m> --suffix-length=4 --numeric-suffix <source_file.tgz> <destination_file.tgz.>

# Extract from splitted files (tgz)
cat <destination_file.tgz.*> | tar -xzvf -

# Compress
zip <filename.zip> <file>

# Extract (`sudo apt install unzip`)
unzip <file_name.zip>
unzip '*.zip'

# Extract (sudo apt-get install unrar)
unrar x -r </path/to/file.rar>

Cron

  1. Create a bash file that starts with #!/bin/bash and without the .sh filename suffix
  2. Change the file to runnable mode with the sudo chmod +x command
  3. ceate a soft link in the /etc/cron.daily/ or add it to the /etc/crontab
  4. Test for correct run: run-parts --test /etc/cron.daily

Xmodmap

xmodmap -e 'remove Mod1 = Alt_R'

xmodmap -e 'add Mod3 = Alt_R'

Firewall

sudo ufw enable/disable

# Show status of firewall and all available ports
sudo ufw status verbose

# Show list of apps that need firewall access
sudo ufw app list

sudo ufw allow <port>
sudo ufw delete allow <port>

sudo ufw allow in "<app name>"
sudo ufw delete allow in "<app name>"

Add Proxy To Apt-Get

  1. Go to https://free-proxy-list.net/ and find an free proxy address

  2. Add below code to /etc/apt/apt.conf:

    # If your proxy has not password
Acquire::http::Proxy "http://<yourproxyaddress>:<proxyport>";

# If your proxy has password
Acquire::http::Proxy "http://<username>:<password>@<proxyaddress>:<proxyport>";

Remove Launcher Entry

  1. Go to ~/.local/share/applications/ or /usr/share/applications/
  2. Remove <your application name: jetbrains-pycharm.desktop>

Networkmanager

nmcli connection

nmcli connection modify <connection name> ipv4.dns "<dns one:8.8.8.8> <dns two:8.8.4.4>"

# Needs to restart
nmcli connection down <connection name>

# Needs to restart
nmcli connection up <connection name>

Tmux

# Create simple session
tmux

# Create named session
tmux new -s <session_name>

# Create window (tab)
ctrl+b c

# Connect to simple session
tmux attach-session
tmux a

# Connect to named session
tmux attach-session -t <session_name>

# Disconnect from session
ctrl+b + d

# Destroy session
ctrl+d

# Vertically
ctrl+b %

# Horizontally
ctrl+b "

Grub

sudo vim /etc/default/grub
sudo update-grub

  1. To install and fix grub, you need Live CD or Live USB of Ubuntu

  2. Once you load Live Ubuntu, Open Terminal and fire following commands to install boot-repair and let it fix the Grub

    sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
sudo apt-get install -y boot-repair && boot-repair

  3. After installation, boot-repair will get automatically launched

  4. Make sure to select "recommended repair" option to repair grub. Reboot

  5. You will now have a Grub menu on boot, where you can choose from Ubuntu, and Windows

sudo os-prober
sudo update-grub

Disable Sudo Password

  1. Run:

    sudo EDITOR=vim visudo

  2. And add below line after the %sudo line:

    # For specific user
<username> ALL=(ALL) NOPASSWD: <command: /bin/systemctl>

# For all users
ALL ALL=(ALL) NOPASSWD: <command: /bin/systemctl>

Machine

cat /etc/*-release

lscpu

free -h

# Simple
df -h

# Advanced
ncdu

# .dev
sudo dpkg -i path/to/file.deb
sudo apt-get install -f

# .rpm
sudo alien -i path/to/file.rpm

cat /etc/fstab

# If there is a line like `UUID=xxx /boot/efi ntfs defaults 0 1`, it means the system boot mode is UEFI, otherwise, it is Legacy BIOS

dmesg -l err

Nvidia Driver

  1. First we will install the proper driver:

    sudo apt install nvidia-detect
nvidia-detect
sudo apt install <suggested_package_from_previous_step>

  2. After restarting the system driver should work properly, if not we will install the below packages:

    sudo apt-get install bumblebee bumblebee-nvidia linux-headers-generic

  3. Now each time that we want to use the NVIDIA GPU should run the following command! (While the following command is runnuing we can run every program that we want to use NVIDIA GPU)

    sudo optirun nvidia-settings -c :8

Gnome

dconf reset -f /org/gnome/shell/extensions/<extension_name>

Mount & Partition

sudo lsblk

sudo fdisk /dev/sda

... Command (m for help): n
... Select (default p): p
... Partition number (1-4, default 1):
... First sector (46483456-62914559, default 46483456):
... Last sector, +/- sectors or +/-size{K,M,G,T,P} (46483456-62914559, default 62914559):

... Command (m for help): w

sudo mkfs.ext4 /dev/sda1

sudo mkdir /sample_dir

sudo mount /dev/sda1 /sample_dir  # for mount
sudo umount /sample_dir  # for unmount

sudo mkdir /source_dir
sudo mkdir /destination_dir

sudo mount --bind /source_dir /destination_dir

sudo fsck -N /dev/sda1

Alt+Shift+any_other_key Doesn't Work

The problem is related to the change-layout shortcut, by default it is set to Alt+Shift, for this reason, the system intercepts it for itself and doesn't let it reach some programs like Pycharm or VSCode.

To solve, update /etc/default/keyboard and replace

XKBOPTIONS="grp:alt_shift_toggle,grp_led:scroll"

with

XKBOPTIONS="grp:super_space_toggle,grp_led:scroll"

Other

  • Minimal Curl:

    curl -i -H "Accept: text/html" 127.0.0.1:31001 -v

  • Vim replace all:

    :%s/foo/bar/g

  • Open shell without login:

    ctrl + alt + f5