Image Credit: Shutterstock
Most people run Linux on Raspberry Pi and its "official" operating system is a version of Debian called Raspbian that's been modified just for the Pi. From a typical user perspective, the default Raspbian desktop user interface is similar to Windows, with a main menu and system tray on the desktop along with icons for common applications.
However, like all forms of Linux, Raspbian has a powerful command line interface that gives you a lot more control over the computer than you can get using the GUI. And many important tasks are either easier or only possible via commands. That's why, below we've listed the most important commands for navigating the file system, installing software, editing files and monitoring performance.
Opening a Terminal
To open a terminal from the Windows GUI, either click the Terminal icon (it looks like a tiny monitor) or hit CTRL+ ALT + T. Once open, you will see a black screen appear with a flashing prompt. If you connect to your Pi via SSH or you already booted to the command prompt, you don't need to open terminal, because you're already there.
This prompt is telling us that we are logged in as a user called pi and that our machine is called raspberry pi. The $ refers to our permissions, in that we have permission to edit any file or folder in our home directory, which in this case is /home/pi/.
In our home directory we can store our work, projects, pictures etc. But we cannot harm the underlying filesystem as we do not have permission to do so. To make system wide changes we either need to be a user called “root” which has similar powers to administrator on Windows, or we need to use sudo (see below) to temporarily give us extra permissions. In this guide we shall cover this and much more.
So let's start our adventure by testing out a few commands and learning more about home our Raspberry Pi works.
sudo - Super User Do
By default, Raspbian, like all forms of Linux doesn't give you the admin privileges you need to perform some core tasks like installing software. However, by prefacing any command with the word "sudo," you can have admin rights for that execution. To use "sudo," you will have to be in the "subdoers" permission group, but the good news is that the default Raspberry Pi user is already in this group.
For example, to upgrade your operating system, you'd type:
sudo apt upgrade
Configuring Your Pi
Whether you want to change your password, enable VNC, overclock your Raspberry Pi or set your Wi-Fi network from the terminal, the easiest way is by using the configuration tool. To launch it, simply type:
Navigating the file system
Moving around the filesystem is something we take for granted in a GUI environment. But with the terminal we can do everything, and with great speed and precision. We just need to know the correct commands. If you don't have permission to perform any of these actions on a particular file or directory, prefacing the command with sudo will probably let you.
pwd - Print working directory
This command will show the full path to the directory we are in, for example /home/pi/.
ls - List directory content
This command is used to list the contents of a directory.
List files in your current directory.
List the files in another directory, such as /var/log:
See hidden files and directories, in a long list with extra details.
List all files of a certain type, for example .py Python files.
cd - Change directory
Using this command we can move around the filesystem. For example to move from our home directory to Downloads
Move to a directory in another part of the filesystem, for example /var/log.
Go back to the previous directory that we were in.
Go back to our home directory.
Working with files
Sometimes we need to take a peek inside a file, look for a specific command, error or bug and with these commands we can do just that all from the terminal.
cat - Print files to the terminal
Print the contents of a file to the terminal, for example a Python file.
Print contents of the file to the terminal with line numbers.
cat -n test.py
less - Print files to the terminal
This command will print the contents of a file in sections and we can scroll through the file using the arrow keys, Page Up / Down and Home / End.
grep - Looking inside a file
To search inside a file for a specific word / section of text. Typically used with log files when looking for issues. In this example we use lscpu to print the details of the CPU which is passed via a pipe | to grep which we instruct to look for “MHz”.
lscpu | grep “MHz”
Edit a file
For when you quickly need to edit a config file, Python code or just write a to do list.
Nano is the easiest command-line editor for beginners.
Create a new file, for example newfile.txt.
Edit an existing file, for example test.py.
Inside nano we navigate using the arrow keys and it works just like a regular text editor.
Save your work.
CTRL + O
Confirm filename, Press Enter
CTRL + X
System Resources & Management
Managing our operating system and checking system resources is standard practice in the terminal. Here we show a few commands to get you started.
htop - Display system processes
Shows the current CPU load, RAM usage and running system processes. Installed by default on Raspbian. Useful for closing non responsive applications.
free - Show amount of free and used RAM
This command will tell us how much RAM is in use, and what is free for applications. Using the -m option we can set the values in MB.
dmesg - Monitor kernel events
The kernel is the core of the operating system and with dmesg we can see what events are happening behind the scenes. Useful for debugging issues with devices.
Moving, deleting, copying and creating new files and directories are some of the most basic actions that we need to do. From the terminal we can do that and much more.
mv - Move / rename a file
This command offers two functions. We can move a file from one location to another. For example here we move test.py to the Documents directory.
mv test.py Documents/
The command can also be used to rename a file or directory. Here we rename test.py to test2.py.
mv test.py test2.py
rm - Delete a file
With this command we can delete files and directories. In this example we delete the file test.py.
cp - Copy a file
To copy a file, for example test.py to our Documents directory.
cp test.py Documents/
To copy a directory, for example /home/pi/test2 to /home/pi/Documents/ we need to use the -r option to copy everything across.
cp -r test2/ Documents/
mkdir - Create a directory
Create a new directory to store work. For example let's create a directory called Work in our home directory.
Just like any computer we need to make sure that our software is up to date and on our Raspberry Pi the tool to do just that is called apt.
apt - Install and manage software
Apt, the Advanced Packaging Tool. The app store of Linux. To use apt we will need to use sudo as it will make changes to the operating system.
First we update the list of installable software.
sudo apt update
Then we can install a specific application, for example to install vlc.
sudo apt install vlc
Or we can upgrade all of the software on our Raspberry Pi. Note that for this command we pass the -y option to automatically agree to install every package. But this is optional.
sudo apt upgrade -y
Network Connectivity & Internet
Checking that your Raspberry Pi is connected to the Internet is a basic yet crucial task. It enables us to debug our IoT projects and watch YouTube videos.
ping - Check that we are connected
The ping command is used to test that our Raspberry Pi is connected to the Internet / home network.
We can send a ping to a website.
Or to an IP address such as Google’s DNS server.
Or for internal connectivity checks we can send a ping to devices on our home network. This example assumes that our IP range is 192.168.1.1 but your range may be different.
hostname - Get the IP address of your Raspberry Pi
The easiest way to find the IP address of our Raspberry Pi is using hostname with the -I (uppercase i) which will show all IP addresses (WiFi and Ethernet)
Curl - Transfer data over a network
With this command we can transfer a file to and from our Raspberry Pi. For example if we wanted to download an image from a website we would use curl along with the -o option to create a file named image.jpg.
curl http://link-to-theimage.com/image.jpg -o image.jpg
The curl command is particularly useful for downloading installation scripts to automatically install add on boards. But it should be used with caution and any code reviewed before it is used.
The Linux terminal has many secrets and tricks, all designed to save you time and become a keyboard ninja.
The history command will display the history of the commands entered in the terminal. When used it will output all of the commands at once as a long list.
At the start of each line in the list is a number and we can use this number to run that command once again. But we must precede the number with an exclamation mark.
history with grep
By using a pipe “|” with the history command we can send the output of history to grep where we can then search for specific commands. Here we look for all the occurences of “apt” in history.
history | grep “apt”
CTRL + R search
Using this we can interactively search through our command history for a specific command. To start we press CTRL + R together and then start typing part of the command. For example we have just used the history | grep “apt” command so we can now press CTRL + R and start typing history and the search will find that command.
Think of this as “auto complete” for the terminal. The TAB key is located just above the Caps Lock key and we can use TAB completion to help complete long commands, directory listings. If we type in the first few letters of a command, for example his and press TAB it will complete the command to show history.
But if we wanted to complete a long directory path, for example /usr/lib/python3/dist-packages then we could start typing /usr/lib/ and then press TAB to show us all the directories available along that path. We could then start typing python3 and by pressing TAB a few more times, the command will narrow down the options that we can use.
Another way to search through your history is to use the up and down arrow keys. With these keys we can go backwards and forwards through our command history and when the correct command is displayed, press Enter to run.
Using this command we can create shortcuts / short commands from much longer ones. For example here we create an alias called updater and use that to call two commands. The first will update our list of installable software, and if that works successfully, denoted by using “&&” to chain the commands together, then it will run the upgrade on our Raspberry Pi.
alias updater=”sudo apt update && sudo apt upgrade -y”
Now we can run our update command just by typing updater in the terminal. Note that once the Raspberry Pi is switched off, this alias is deleted.