info_tfgrid/collections/sysadmins/computer_it_basics/cli_scripts_basics.md
2024-07-10 21:30:25 -04:00

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CLI and Scripts Basics

Table of Contents


Introduction

We present here a quick guide on different command-line interface (CLI) commands as well as some basic scripts.

The main goal of this guide is to demonstrate that having some core understanding of CLI and scripts can drastically increase efficiency and speed when it comes to deploying and managing workloads on the TFGrid.

Basic Commands

Update and upgrade packages

The command update ensures that you have access to the latest versions of packages available.

sudo apt update

The command upgrade downloads and installs the updates for each outdated package and dependency on your system.

sudo apt upgrade

Test the network connectivity of a domain or an IP address with ping

To test the network connectivity of a domain or an IP address, you can use ping on Linux, MAC and Windows:

  • Template
    ping <IP-Address_Or_Domain>
    
  • Example
    ping threefold.io
    

On Windows, by default, the command will send 4 packets. On MAC and Linux, it will keep on sending packets, so you will need to press Ctrl-C to stop the command from running.

You can also set a number of counts with -c on Linux and MAC and -n on Windows.

  • Send a given number of packets on Linux and MAC (e.g 5 packets)
    ping -c 5 threefold.io
    
  • Send a given number of packets on Windows (e.g 5 packets)
    ping -n 5 threefold.io
    

Install Go

Here are the steps to install Go.

  • Install go
    sudo apt install golang-go
    
  • Verify that go is properly installed
    go version
    

Install Brew

Follow those steps to install Brew

  • Installation command from Brew:
    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
    
  • Add the path to the .profile directory. Replace <user_name> by your username.
    echo 'eval "$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)"' >> /home/<user_name>/.profile
    
  • Evaluation the following:
    eval "$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)"
    
  • Verify the installation
    brew doctor
    

Brew basic commands

  • To update brew in general:
    brew update
    
  • To update a specific package:
    brew update <package_name>
    
  • To install a package:
    brew install <package_name>
    
  • To uninstall a package:
    brew uninstall <package_name>
    
  • To search a package:
    brew search <package_name>
    
  • Uninstall Brew
    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/uninstall.sh)"
    

Install Terraform with Brew

Installing Terraform with Brew is very simple by following the Terraform documentation.

  • Compile HashiCorp software on Homebrew's infrastructure
    brew tap hashicorp/tap
    
  • Install Terraform
    brew install hashicorp/tap/terraform
    

Yarn basic commands

  • Add a package
    yarn add
    
  • Initialize the development of a package
    yarn init
    
  • Install all the dependencies in the package.json file
    yarn install
    
  • Publish a package to a package manager
    yarn publish
    
  • Remove unused package from the current package
    yarn remove
    
  • Clean the cache
    yarn cache clean
    

Set default terminal

update-alternatives --config x-terminal-emulator

See the current path

pwd

List hidden files

ls -ld .?*

Display the content of a directory

You can use tree to display the files and organization of a directory:

  • General command
    tree
    
  • View hidden files
    tree -a
    

Vim modes and basic commands

Vim is a free and open-source, screen-based text editor program.

With Vim, you can use two modes.

  • Insert mode - normal text editor
    • Press i
  • Command mode - commands to the editor
    • Press ESC

Here are some basic commands:

  • Delete characters
    • x
  • Undo last command
    • u
  • Undo the whole line
    • U
  • Go to the end of line
    • A
  • Save and exit
    • :wq
  • Discard all changes
    • :q!
  • Move cursor to the start of the line
    • 0
  • Delete the current word
    • dw
  • Delete the current line
    • dd

Check the listening ports using netstat

Use the command:

netstat

See the disk usage of different folders

du -sh *

Verify the application version

which <application_name>

Find the path of a file with only the file name

On MAC and Linux, you can use coreutils and realpath from Brew:

brew install coreutils
realpath file_name

Become the superuser (su) on Linux

You can use either command:

  • Option 1
    sudo -i
    
  • Option 2
    sudo -s
    

Exit a session

You can use either command depending on your shell:

exit
logout

Know the current user

You can use the following command:

whoami

See the path of a package

To see the path of a package, you can use the following command:

whereis <package_name>

Set the path of a package

export PATH=$PATH:/snap/bin

See the current path

pwd

Find the current shell

  • Compact version
    echo $SHELL
    
  • Detailed version
    ls -l /proc/$$/exe
    

SSH into Remote Server

  • Create SSH key pair
    ssh-keygen
    
  • Install openssh-client on the local computer*
    sudo apt install openssh-client
    
  • Install openssh-server on the remote computer*
    sudo apt install openssh-server
    
  • Copy public key
    cat ~/.ssh/id_rsa.pub
    
  • Create the ssh directory on the remote computer
    mkdir ~/.ssh
    
  • Add public key in the file authorized_keys on the remote computer
    nano ~/.ssh/authorized_keys
    
  • Check openssh-server status
    sudo service ssh status
    
  • SSH into the remote machine
    ssh <username>@<remote_server_IP_or_hostname>
    

*Note: For MAC, you can install openssh-server and openssh-client with Brew: brew install openssh-server and brew install openssh-client.

To enable remote login on a MAC, read this section.

Replace a string by another string in a text file

  • Replace one string by another (e.g. old_string, new_string)
    sed -i 's/old_string/new_string/g' <file_path>/<file_name>
    
  • Use environment variables (double quotes)
    sed -i "s/old_string/$env_variable/g" <file_path>/<file_name>
    

Replace extensions of files in a folder

Replace ext1 and ext2 by the extensions in question.

find ./ -depth -name "*.ext1" -exec sh -c 'mv "$1" "${1%.ext1}.ext2"' _ {} \;

Remove extension of files in a folder

Replace ext with the extension in question.

for file in *.ext; do
    mv -- "$file" "${file%%.ext}"
done

See the current date and time on Linux

date

Special variables in Bash Shell

Special Variables Descriptions
$0 Name of the bash script
$1, $2...$n Bash script arguments
Process id of the current shell
$* String containing every command-line argument
$# Total number of arguments passed to the script
$@ Value of all the arguments passed to the script
$? Exit status of the last executed command
$! Process id of the last executed command
$- Print current set of option in current shell

Gather DNS information of a website

You can use Dig to gather DNS information of a website

  • Template
    dig <website.tld>
    
  • Example
    dig threefold.io
    

You can also use online tools such as DNS Checker.

Partition and mount a disk

We present one of many ways to partition and mount a disk.

  • Create partition with gparted
    sudo gparted
    
  • Find the disk you want to mount (e.g. sdb)
    sudo fdisk -l
    
  • Create a directory to mount the disk to
    sudo mkdir /mnt/disk
    
  • Open fstab
    sudo nano /etc/fstab
    
  • Append the following to the fstab with the proper disk path (e.g. /dev/sdb) and mount point (e.g. /mnt/disk)
    /dev/sdb    /mnt/disk    ext4    defaults    0    0
    
  • Mount the disk
    sudo mount /mnt/disk
    
  • Add permissions (as needed)
    sudo chmod -R 0777 /mnt/disk
    

Encryption

Encrypt files with Gocryptfs

You can use gocryptfs to encrypt files.

  • Install gocryptfs
    apt install gocryptfs
    
  • Create a vault directory (e.g. vaultdir) and a mount directory (e.g. mountdir)
    mkdir vaultdir mountdir
    
  • Initiate the vault
    gocryptfs -init vaultdir
    
  • Mount the mount directory with the vault
    gocryptfs vaultdir mountdir
    
  • You can now create files in the folder. For example:
    touch mountdir/test.txt
    
  • The new file test.txt is now encrypted in the vault
    ls vaultdir
    
  • To unmount the mountedvault folder:
    • Option 1
      fusermount -u mountdir
      
    • Option 2
      rmdir mountdir
      

Encrypt files with Veracrypt

To encrypt files, you can use Veracrypt. Let's see how to download and install Veracrypt.

  • Veracrypt GUI
    • Download the package
      wget https://launchpad.net/veracrypt/trunk/1.25.9/+download/veracrypt-1.25.9-Ubuntu-22.04-amd64.deb
      
    • Install the package
      dpkg -i ./veracrypt-1.25.9-Ubuntu-22.04-amd64.deb
      
  • Veracrypt console only
    • Download the package
      wget https://launchpad.net/veracrypt/trunk/1.25.9/+download/veracrypt-console-1.25.9-Ubuntu-22.04-amd64.deb
      
    • Install the package
      dpkg -i ./veracrypt-console-1.25.9-Ubuntu-22.04-amd64.deb
      

You can visit Veracrypt download page to get the newest releases.

  • To run Veracrypt
    veracrypt
    
  • Veracrypt documentation is very complete. To begin using the application, visit the Beginner's Tutorial.

See the network connections and ports

ifconfig

See identity and info of IP address

  • See abuses related to an IP address:
    https://www.abuseipdb.com/check/<IP_Address>
    
  • See general information of an IP address:
    https://www.whois.com/whois/<IP_Address>
    

ip basic commands

  • Manage and display the state of all network
    ip link
    
  • Display IP Addresses and property information (abbreviation of address)
    ip addr
    
  • Display and alter the routing table
    ip route
    
  • Manage and display multicast IP addresses
    ip maddr
    
  • Show neighbour object
    ip neigh
    
  • Display a list of commands and arguments for each subcommand
    ip help
    
  • Add an address
    • Template
      ip addr add
      
    • Example: set IP address to device enp0
      ip addr add 192.168.3.4/24 dev enp0
      
  • Delete an address
    • Template
      ip addr del
      
    • Example: set IP address to device enp0
      ip addr del 192.168.3.4/24 dev enp0
      
  • Alter the status of an interface
    • Template
      ip link set
      
    • Example 1: Bring interface online (here device em2)
      ip link set em2 up
      
    • Example 2: Bring interface offline (here device em2)
      ip link set em2 down
      
  • Add a multicast address
    • Template
      ip maddr add
      
    • Example : set IP address to device em2
      ip maddr add 33:32:00:00:00:01 dev em2
      
  • Delete a multicast address
    • Template
      ip maddr del
      
    • Example: set IP address to device em2
      ip maddr del 33:32:00:00:00:01 dev em2
      
  • Add a routing table entry
    • Template
      ip route add
      
    • Example 1: Add a default route (for all addresses) via a local gateway
      ip route add default via 192.168.1.1 dev em1
      
    • Example 2: Add a route to 192.168.3.0/24 via the gateway at 192.168.3.2
      ip route add 192.168.3.0/24 via 192.168.3.2
      
    • Example 3: Add a route to 192.168.1.0/24 that can be reached on device em1
      ip route add 192.168.1.0/24 dev em1
      
  • Delete a routing table entry
    • Template
      ip route delete
      
    • Example: Delete the route for 192.168.1.0/24 via the gateway at 192.168.1.1
      ip route delete 192.168.1.0/24 via 192.168.1.1
      
  • Replace, or add, a route
    • Template
      ip route replace
      
    • Example: Replace the defined route for 192.168.1.0/24 to use device em1
      ip route replace 192.168.1.0/24 dev em1
      
  • Display the route an address will take
    • Template
      ip route get
      
    • Example: Display the route taken for IP 192.168.18.25
      ip route replace 192.168.18.25/24 dev enp0
      

References: https://www.commandlinux.com/man-page/man8/ip.8.html

Display socket statistics

  • Show all sockets
    ss -a
    
  • Show detailed socket information
    ss -e
    
  • Show timer information
    ss -o
    
  • Do not resolve address
    ss -n
    
  • Show process using the socket
    ss -p
    

Note: You can combine parameters, e.g. ss -aeo.

References: https://www.commandlinux.com/man-page/man8/ss.8.html

Query or control network driver and hardware settings

  • Display ring buffer for a device (e.g. eth0)
    ethtool -g eth0
    
  • Display driver information for a device (e.g. eth0)
    ethtool -i eth0
    
  • Identify eth0 by sight, e.g. by causing LEDs to blink on the network port
    ethtool -p eth0
    
  • Display network and driver statistics for a device (e.g. eth0)
    ethtool -S eth0
    

References: https://man.archlinux.org/man/ethtool.8.en

See if ethernet port is active

Replace <ethernet_device> with the proper device:

cat /sys/class/net/<ethernet_device>/carrier

Add IP address to hardware port (ethernet)

  • Find ethernet port ID on both computers

    ip a
    
  • Add IP address (DHCO or static)

    • Computer 1
      ip addr add <Private_IP_Address_1>/24 dev <ethernet_interface_1>
      
    • Computer 2
      ip addr add <Private_IP_Address_2>/24 dev <ethernet_interface_2>
      
  • Ping the address to confirm connection

    ping <Private_IP_Address>
    

To set and view the address for either DHCP or static, go to Networks then Details.

Private IP address range

The private IP range is the following:

  • 10.0.0.010.255.255.255
  • 172.16.0.0172.31.255.255
  • 192.168.0.0192.168.255.255

Set IP Address manually

You can use the following template when you set an IP address manually:

  • Address
    • <Private_IP_Address>
  • Netmask
    • 255.255.255.0
  • Gateway
    • optional

Basic Scripts

Run a script with arguments

You can use the following template to add arguments when running a script:

  • Option 1
    ./example_script.sh arg1 arg2
    
  • Option 2
    sh example_script.sh "arg1" "arg2"
    

Print all arguments

  • Write a script
    • File: example_script.sh
      #!/bin/sh
      echo $@
      
  • Give permissions
    chmod +x ./example_script.sh
    
  • Run the script with arguments
    sh example_script.sh arg1 arg2
    

Iterate over arguments

  • Write the script

      # iterate_script.sh
      #!/bin/bash 
      for i; do 
        echo $i 
      done
    
  • Give permissions

    chmod +x ./iterate_script.sh
    
  • Run the script with arguments

    sh iterate_script.sh arg1 arg2
    
  • The following script is equivalent

      # iterate_script.sh
      #/bin/bash 
      for i in $*; do 
        echo $i 
      done
    

Count lines in files given as arguments

  • Write the script
    # count_lines.sh
    #!/bin/bash
     for i in $*; do
            nlines=$(wc -l < $i)    
            echo "There are $nlines lines in $i"
    done
    
  • Give permissions
    chmod +x ./count_lines.sh
    
  • Run the script with arguments (files). Here we use the script itself as an example.
    sh count_lines.sh count_lines.sh
    

Find path of a file

  • Write the script
    # find.sh
    #!/bin/bash
    
    find / -iname $1 2> /dev/null
    
  • Run the script
    sh find.sh <filename>
    

Print how many arguments are passed in a script

  • Write the script
    # print_qty_args.sh
    #!/bin/bash
    echo This script was passed $# arguments
    
  • Run the script
    sh print_qty_args.sh <filename>
    

Linux

Install Terraform

Here are the steps to install Terraform on Linux based on the Terraform documentation.

wget -O- https://apt.releases.hashicorp.com/gpg | sudo gpg --dearmor -o /usr/share/keyrings/hashicorp-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/hashicorp-archive-keyring.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/hashicorp.list
sudo apt update && sudo apt install terraform

Note that the Terraform documentation also covers other methods to install Terraform on Linux.

MAC

Enable remote login on MAC

  • Option 1:
    • Use the following command line:
      systemsetup -setremotelogin on
      
  • Option 2
    • Use System Preferences
    • Go to System Preferences -> Sharing -> Enable Remote Login.

Find Other storage on MAC

  • Open Finder > Go > Go to Folder
  • Paste this path
    ~/Library/Caches
    

Sort files by size and extension on MAC

  • From your desktop, press Command-F.
  • Click This Mac.
  • Click the first dropdown menu field and select Other.
  • From the Search Attributes window
    • tick File Size and File Extension.

Windows

Install Chocolatey

To install Chocolatey on Windows, we follow the official Chocolatey website instructions.

  • Run PowerShell as Administrator
  • Check if Get-ExecutionPolicy is restricted
    Get-ExecutionPolicy
    
    • If it is restricted, run the following command:
      Set-ExecutionPolicy AllSigned
      
  • Install Chocolatey
    Set-ExecutionPolicy Bypass -Scope Process -Force; [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; iex ((New-Object System.Net.WebClient).DownloadString('https://community.chocolatey.org/install.ps1'))
    
  • Note: You might need to restart PowerShell to use Chocolatey

Install Terraform with Chocolatey

Once you've installed Chocolatey on Windows, installing Terraform is as simple as can be:

  • Install Terraform with Chocolatey
    choco install terraform
    

Find the product key

Write the following in Command Prompt (run as administrator):

wmic path SoftwareLicensingService get OA3xOriginalProductKey

Find Windows license type

Write the following in Command Prompt:

slmgr /dli

References