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Linux Terminal

Here are some basic understandings and commands that can be used on UNIX terminal and eventually on Mac.

Mac Specific

Macbook Air

  • Text input source British PC aligns correctly to british keyboards with
    • left to 1 as backtick and negation
    • left to Z as backslash and pipe \\ |
    • left to enter as hash and tilde, ~ #
    • " above 2, and @ above ?.

Mac Tools

# SQL Client for MySQL, Postgre
brew install --cask sequel-ace

Homebrew

  • package manager for mac,
    • cask are usually GUIs apps like Sublime.
    • formulae are packages, CLIs, like node.

Brew Global Commands:

  • brew update - Update brew and cask list, not packages
  • brew upgrade - Upgrade all packages
  • brew list - List installed packages and casks
  • brew outdated - List outdated packages?
  • brew doctor - Diagnose brew issues
  • brew cleanup - cleans all packages
  • brew services list- lists all services installed

Brew Commands:

  • brew install git - Install a package
  • brew uninstall git - Remove/Uninstall a package
  • brew upgrade git - Upgrade a package
  • brew switch git 2.5.0 - Change versions
  • brew list --versions git See what versions you have
  • brew cleanup git Remove old versions

Brew Cask (GUI) commands:

  • brew install --cask firefox Install the Firefox browser
  • brew list --cask List installed applications

Mac Command Line

Check defaults before altering hidden settings in OS X

# defaults action target variable value
defaults write com.apple.Finder AppleShowAllFiles true
defaults read com.apple.Finder AppleShowAllFiles

# clear defaults
# defaults delete target variable
defaults delete com.apple.Finder AppleShowAllFiles

# dock size
defaults read com.apple.Finder AppleShowAllFiles
defaults read com.apple.dock tilesize
# 64

# on 1920x1200, set dock size 41 to capture 1080p without mac menu bar and app title bar
defaults write com.apple.dock tilesize -int 41; killall Dock

# on 1920x1200, set dock size 41 to capture 1080p from top
defaults write com.apple.dock tilesize -int 99; killall Dock

Others

diskutil list - lists all disks

Format a disk from Mac terminal:

  • diskutil eraseDisk FILE_SYSTEM DISK_NAME DISK_IDENTIFIER
  • eg: diskutil eraseDisk FAT32 VY_Disk /dev/disk2 or use ExFAT
  • /Volumes/PenDrive location of usb mounts

Copy to clipboard

  • $ pbcopy < my_filename.ext it copies the content of file to clipboard.
  • It is helpful to quickly copy RSA key to clipboard which you need to paste on, may be, GitHub.

Androids

  • ~/.android - google utility folder
  • avdmanager list avd - lists all android virtual devices installed.

Uninstalling: Usually check for following dirs and remove:

  • sudo rm /usr/local/mypkg
  • sudo rm -rf /usr/local/var/mypkg
  • sudo rm -rf /usr/local/mypkg*
  • sudo rm -rf /Library/StartupItems/mypkg*
  • sudo rm -rf /Library/PreferencePanes/MyPkg*
  • rm -rf ~/Library/PreferencePanes/MyPkg*
  • sudo rm -rf /Library/Receipts/mypkg*
  • sudo rm -rf /Library/Receipts/MyPkg*

Ubuntu Specific

  • what? - Ubuntu is debain based os, others are Mint, Elementary and PoP OS.

    • Packages Installation & Managemet - apt pkg dpkg
      • Packages are maintained in repositories, Main, Universe, Restricted and Multiverse. You can enable the repo based on your requirement.
      • Debain uses dpkg packaging system, for install/uninstall software.
      • PPA - Personal Package Archive - allows application developers to create their own repositories to distribute.
    • APT - Advanced Package Tool
      • it is CLT UI that works with core libraries to handle the installation and removal of software on Debian, Ubuntu. IT manages dependencies, config files and upgrades/downgrades. apt-get performs installation, search, updates to pkg available on system. works with sudo only.
      • apt=most common used command options from apt-get and apt-cache. It is high level wrapper on old apt-get. Use apt for better UI and info like summary and progress bar.
      • dpkg does not handle dependency, while apt does. apt under the hood uses dpkg.

Tasks

  • Add repository
    • sudo add-apt-repository universe
    • `` add a PPA repo
# Enable a repo
sudo add-apt-repository universe

# Add a repo
sudo add-apt-repository ppa:whatever/ppa

# list the repos added to system
sudo add-apt-repository --list

# Remove repo
sudo add-apt-repository --remove ppa:whatever/ppa

Here, when you enable a repo, itmeans packages can be searched in this repository

  • Update and Upgrade
    • sudo apt-get update - updates local copy of packages database. The result has :
      • Hit: no change in pkg
      • Get: update available, downloads details but not the update
      • Ign: ignores.
    • sudo apt-get upgrade updates core system and apps installed.
    • Update one package - sudo apt-get upgrade [package_name].

  • Install and remove / uninstall

    • sudo apt-get install [pkg1] [pkg2] if you know the name of apps.
    • sudo apt-get remove [package_name] to uninstall. but kepps config files.
    • sudo apt-get autoremove cleans up unwanted pkg.
    • apt list --installed see all that's installed.
    • Install a .deb file, eg, Chrome. You can use apt or dpkg. apt is manager and takes care of dependecies.
      • sudo apt install ./name.deb to install with dependencies, or
      • sudo dpkg -i /path/to/foo.deb installs, then sudo apt-get install -f fix-broken dependencies.

First Steps

Do following in a new install

  • update and upgrade sudo apt update && sudo apt upgrade
  • codecs flash and fonts sudo apt install ubuntu-restricted-extras
  • vlc - sudo apt install vlc
  • chrome wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb then sudo dpkg -i google-chrome-stable_current_amd64.deb
  • more - https://itsfoss.com/things-to-do-after-installing-ubuntu-20-04/

Clean up

  • Delete apps - sudo apt purge thunderbird
  • remove sw dependencies sudo apt autoremove
  • remove partially installed packages sudo apt autoclean
  • remove cache sudo apt clean

Speed up

  • disable animations gsettings set org.gnome.desktop.interface enable-animations false

Dev Softwares

  • sublime sudo snap install sublime-text --classic
  • vs code sudo snap install code --classic

Install Git and Gh:

  • install git and essentials sudo apt-get install build-essential procps curl file git
  • set up git - git config --global user.name "YOUR NAME"
  • set up git - git config --global user.email "YOUR EMAIL ADDRESS"

Install Jupyter notebook, see Python Notes https://iyadavvaibhav.github.io/python-notes/

Install nsepa and Citrix Workspace:

  • wget http://ftp.br.debian.org/debian/pool/main/n/network-manager/libnm-util2_1.6.2-3+deb9u2_amd64.deb http://ftp.br.debian.org/debian/pool/main/n/network-manager/libnm-glib4_1.6.2-3+deb9u2_amd64.deb download debs
  • sudo apt install ./libnm-util2_1.6.2-3+deb9u2_amd64.deb ./libnm-glib4_1.6.2-3+deb9u2_amd64.deb install the debs downloaded
  • Download .deb file from Citrix, amd 64
  • cd ~/Downloads
  • sudo dpkg -i icaclient_21.4.0.11_amd64.deb
  • sudo apt-get install -f

Others

  • lsblk lists disk

Check graphics card installed

  • check hardware using lshw (list hardware) is a small Linux/Unix tool which is used to generate the detailed information of the system's hardware configuration from various files in the /proc directory. E.g. to see graphics driver - sudo lshw -c video
  • check loaded modules using lsmod - it shows which loadable kernel modules are currently loaded. lsmod | grep radeon
  • The glxinfo program shows information about the OpenGL and GLX implementations running on a given X display. sudo apt install mesa-utils and glxinfo -b
  • Check boot message for graphics card in use dmesg | grep -i radeon

Windows on Linux

Users and Groups

List all users

  • getent passwd
  • compgen -u
  • cut -d: -f1 /etc/passwd

List all groups

  • compgen -g

Add user to group - sudo adduser username group

OS Setup and Virtualization

USB Installation

Virtual box add on:

  • sudo apt update
  • sudo apt install virtualbox-guest-dkms virtualbox-guest-x11 virtualbox-guest-utils

Securing Ubuntu Server

Firewall

# install firewall
$ sudo apt-get install -y ufw

# enable ports required
$ sudo ufw allow ssh
$ sudo ufw allow http
$ sudo ufw allow 443/tcp

# Add to startup
$ sudo ufw --force enable
Firewall is active and enabled on system startup

# Check status
$ sudo ufw status

This will install ufw, the Uncomplicated Firewall. Allow external traffic on port 22 (ssh), 80 (http) and 443 (https) only, rest ports are declined.

Fail2ban

# Install fail2ban
$ sudo apt install fail2ban
# keeps logs of login attempts and bans if multiple failed attempts are done```

SSH Only Login

Restric to ssh login and no root login. Do nano /etc/ssh/sshd_config and add

PubkeyAuthentication yes
PermitRootLogin no

and do

systemctl restart ssh

User Management

# Add user
$ adduser john


# make user root user
$ usermod -aG sudo john
Here, it adds user john to sudo group. -a, --append is to add group, use with -G. And -G, --groups GROUP1[,GROUP2,...[,GROUPN]] is to add groups.

# switch user
$ su john

Links

SSH - Secure Shell Protocol

Secure Shell Protocol (SSH) is a network protocol that lets a user access a computer securely over an unsecured network. It uses cryptography to secure communication. It also lets connect using keys and thus avoiding to provide username and password/token on each request.

View your RSA Keys

RSA keys are stored in your user-directory

$ ls ~/.ssh
config  id_rsa  id_rsa.pub  known_hosts

if id_rsa and id_rsa.pub exist then you have rsa keys, else

Generate Your SSH Keys

Every machine need to have SSH public and private key to authenticate. To generate key:

$ ssh-keygen

RSA Public Key

File id_rsa.pub has your public key, it represents you as a user in crytic key. This is secret, but can be givent to servers (vm, github etc.), so that they have your public key and can authenticate you without password. If a public key of a client-machine is in servers authorized keys, then connection from client-machine is authorized without requiring password of user.

Adding your Key to Server

On Server your have logged in with password. Copy your public key from your client machined, then on the server do:

$ echo <your-copied-public-key> >> ~/.ssh/authorized_keys
$ chmod 600 ~/.ssh/authorized_keys

This adds your key to server. Then 600 changes permission to -rw------- from -rw-rw-r-- so that it is secure and only current user can read write it. More information can be found here on Miguel's Linux Deployment Guide

On Github.com - Copy the content of Public RSA Key, then open GitHub, click your profile icon, settings, SSH and GPC Keys, Click on the new ssh key button. Enter any title (usually your user and machine) and key that you copied. This key lets the user and machine be identified without password. More on this here

Once added, the concept is that ssh command on your terminal will do a cryptographic operation with your private key then this magic is sent to server which uses your copied public key to validate and authorize you. GULP it for now..!

What is the known_hosts file in SSH?

The known_hosts file stores the public keys of the server accessed by a user (on client). It stores identity of server so that user accidently does not connect to unknown host and get attacked. They are stored in /etc/ssh/known_hosts for system hosts or in ~/.ssh/known_hosts for each user.

If the host is unknow you see following message:

$ ssh -p 2222 vaibhav@127.0.0.1
The authenticity of host '[127.0.0.1]:2222 ([127.0.0.1]:2222)' can't be established.
ED25519 key fingerprint is SHA256:UystFEOFRcH1YLdhYgr543JgrecGeZ2jmg02naQQZVw.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '[127.0.0.1]:2222' (ED25519) to the list of known hosts.

Otherwise it simply lets connect.

Install SSH Server and Enable on Ubuntu

Any server needs to run SSH server and enable SSH port on itself so that it can accept SSH connections.

# install ssh
sudo apt install openssh-server

# view status
sudo systemctl status ssh

# allow ssh port on firewall
sudo ufw allow ssh

# get IP address of ubnutu machine
ip a

You need to secure Ubunut server as well to prevent misuse, see "Securing Ubuntu Server" for more details.

Now this machine can accept SSH connections.

SCP - File Transfer via SSH

To copy a file:

# Syntax
scp <source> <destination>

# To copy a file from B to A while logged into B:
scp /path/to/file username@a:/path/to/destination

# To copy a file from B to A while logged into A:
scp username@b:/path/to/file /path/to/destination

If you want to copy a directory from machine a to b while logged into a:

scp -r /path/to/directory user@machine_b_ipaddress:/path/to/destination

If you want to copy a directory from machine a to b while logged into b:

scp -r user@machine_a_ipaddress:/path/to/directory /path/to/destination

Example:

scp -r .\abc\ john@192.168.10.10:/tmp/abc

Linux Ways

  • alias vynote="subl ~/path/to/file/notepad.txt" add to .bash_profile to make shortcut

ENVs:

  • source activate [path to env] activates env
  • source deactivate deactivates enn

Emac Basic

  • Press ctrl + c + x to save and exit a file.

Other

  • everything global is installed in /usr/local/bin/
  • use PostMan for http requests to REST routes
  • rmdir removed empty dir
  • rm -rf removes non/empty dir and files forcefully
  • rm removes files not directories.
  • ls - shows file in dir
    • ls -l as a list
    • ls -h human readable sizes
    • ls -r reverse order
    • ls -t sorts by last modified date and time, default is latest at top
    • ls -a shows all, includes hidden files
    • Examples
      • ls -lt | head shows last 10 modified files.
  • head/tail - show first or last lines
    • head -n 2 - --lines - shows first 2 lines.
    • Examples
      • ls -lt | head -n 5 shows only 5 files from prev command.
      • head -5 notes.txt - shows top 5 lines from file.

Find and Delete

# find and delete files
find ./path/to/dir -name "*.db" -type f -exec rm "{}" +

Shell Configuration

.zprofile is same as .bash_profile is for bash shell. Also same as .zshenv, this file is to set path and env.

.zshrc is to set look and feel.

To make zsh use auto-suggestiona and syntax highlight

brew install zsh-syntax-highlighting zsh-autosuggestions

Then, add to ~/.zshrc:

# >>> Syntax Highlight Begins >>>
autoload -Uz colors
autoload -Uz compinit
autoload -Uz down-line-or-beginning-search
autoload -Uz up-line-or-beginning-search
autoload -Uz vcs_info

colors
compinit

zle -N down-line-or-beginning-search
zle -N up-line-or-beginning-search

bindkey "^[[A" up-line-or-beginning-search
bindkey "^[[B" down-line-or-beginning-search
bindkey "${terminfo[kcuu1]}" up-line-or-beginning-search
bindkey "${terminfo[kcud1]}" down-line-or-beginning-search
bindkey "${terminfo[kcbt]}" reverse-menu-complete
bindkey "${terminfo[kdch1]}" delete-char

precmd_functions+=(vcs_info)
vcs_info_format="%{$fg_bold[cyan]%}(%{$fg_bold[red]%}%b%{$fg_bold[cyan]%}) "

zstyle ':completion:*' menu select
zstyle ':vcs_info:*' enable git
zstyle ':vcs_info:*' formats "$vcs_info_format"
zstyle ':vcs_info:*' actionformats "$vcs_info_format"

export PROMPT='%(?:%{$fg_bold[green]%}:%{$fg_bold[red]%})➜ %{$fg_bold[cyan]%}%c %{$vcs_info_msg_0_%}%{$reset_color%}'
setopt PROMPT_SUBST

export HISTFILE=~/.zsh_history
export HISTSIZE=10000
export SAVEHIST=1000000
setopt SHARE_HISTORY
setopt HIST_FIND_NO_DUPS

setopt AUTOCD

source /opt/homebrew/share/zsh-autosuggestions/zsh-autosuggestions.zsh
source /opt/homebrew/share/zsh-syntax-highlighting/zsh-syntax-highlighting.zsh

# <<< Syntax Highlight Ends <<<

youtube-dl

  • youtube-dl --extract-audio --audio-format mp3 -o "%(title)s.%(ext)s" http://www.youtube.com/watch?v=fdf4542t5g -o is --output of filename.

Termux - Linux on Android

  • pkg is similar to apt, it is another package manager in termux, it is even higher wrapper on apt. You can use both.
  • Installing termux
    • Termux is no more updated on play store, so you can use old or download latest from F-droid.org

    • Once installed do following on phone

      termux-setup-storage
termux-change-repo # (I selected Albatros)
pkg update && pkg upgrade
exit

  • Enabling SSH

    • SSH lets you use phone linux from another laptop. Do this on phone:

      pkg update && pkg upgrade
pkg install openssh -y # ssh server is now installed
passwd # set a password to login from another device
sshd  # It's time to run the server
ifconfig # to check the IP of phone, ensure wifi is enabled
    • Now open cmd or terminal on a machine connected to same wifi and do ssh 192.168.1.17 -p 8022, where IP is address of phone.
  • Termux - working with packages
    • Search: pkg search <query>
    • Install: pkg install <package>
    • Upgrade: pkg upgrade
  • Termux - subscribing to additional repositories
    • Root: pkg install root-repo
    • X11: pkg install x11-repo

  • Setting Python and Git

    pkg install python -y
pkg install git -y

  • Crontab on Termux

    • it is used to schedule jobs in linux and make them run at certain intervals.

      pkg install cronie termux-services
sv-enable crond

# `service-daemon start` or restart terminal 

~/code$ crontab -l
no crontab for u0_a234

crontab -e 

0 * * * * cd /data/data/com.termux/files/home/code && /data/data/com.termux/files/usr/bin/python tbd_logger.py
    • Example run logs
      • time 2023-04-22 19:39 - battery 85% - cron at 1m
      • time 2023-04-23 12:22 - battery 68% - cron switched to 1hr

Alpine Linux

Installation detailed steps can be found in this Alpine Linux Virtual box Guide

Mobile Linux

Everything related to iOS and Android Linux.

Install Termux App on Android.

termux-setup-storage
termux-change-repo
pkg update

pkg install git
git --version

pkg install python

pkg install openssl

pip install --upgrade youtube-dl

youtube-dl -i PLyAyDdlMr3GOHFBt0IzgvED-n3uhwyrhd

Install on a-Shell iOS App

cd ~/code
wget -qO- http://dl-cdn.alpinelinux.org/alpine/v3.12/main/x86/apk-tools-static-2.10.6-r0.apk | tar -xz sbin/apk.static && ./sbin/apk.static add apk-tools && rm sbin/apk.static
apk add python3
apk add py3-pip
pip install youtube-dl
2025-01-12 Jul 2018