With reference to the man pages you might even be able to glean exactly what the command is doing, or at least get a general idea. On a Ubuntu 18.04 system you can find a launcher for the terminal by clicking on the Activities item at the top left of the screen, then typing the first few letters of “terminal”, “command”, “prompt” or “shell”. They’re all just different ways of asking you to open a terminal to get to a shell. They’re best used when you need a reminder of a particular switch or parameter, rather than as a general resource for learning how to use the command line. Let’s move it back to the working directory. In the same way that two dots (..) represents the parent directory, so a single dot (.) This tutorial includes some specfic steps for Ubuntu 18.04 but most of the content should work regardless of your Linux distribution. registered trademarks of Canonical Ltd. How to access the command line from your own computer, How to perform some basic file manipulation, How to chain commands together to make more powerful tools, A computer running Ubuntu or some other version of Linux. In the following command you’ll need to replace USERNAME with your own username, the whoami command will remind you of your username, in case you’re not sure: There’s one other handy shortcut which works as an absolute path. All it does is print out the shell’s current working directory. Despite that, human nature being what it is, many administrators over the years have been guilty of using root as their main, or only, account. Linux ubuntu-16-04-1 4.4.0-57-generic #78-Ubuntu SMP Fri Dec 9 23:50:32 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux Also, the hostnamectl command can help you get the version of Ubuntu you are running hostnamectl You should more easily be able to tell what files they’re manipulating, or what other switches and parameters are being used. If the instructions require you to first add a new software repository to your system, using the apt-add-repository command, by editing files in /etc/apt, or by using a “PPA” (Personal Package Archive), you should be careful as these sources are not curated by Canonical. We’ll look at the superuser account more in section 7. Often referred to as the shell, terminal, console, prompt or various other names, it can give the appearance of being complex and confusing to use. So far we’ve only seen commands that work on their own (cd, pwd) or that have a single item afterwards (cd /, cd ~/Desktop). This guideline may seem restrictive, but if you end up using the command line with any frequency you’ll be glad you stuck to this pattern. Double-lick to get the command line as shown in the following screenshot. Check Ubuntu Version in Bash Command Line. To clear the screen, we can use the clear command. In this screenshot of Ubuntu 18.04 you can see the option at the top of the dialog: Assuming you’re on a Linux system that uses sudo, and your account is configured as an administrator, try the following to see what happens when you try to access a file that is considered sensitive (it contains encrypted passwords): If you enter your password when prompted you should see the contents of the /etc/shadow file. If you look at the output of ls you’ll notice that the only files or folders that start with “t” are the three test files we’ve just created, so you could even simplify that last command even further to cat t*, meaning “concatenate all the files whose names start with a t and are followed by zero or more other characters”. Let’s install a new command line program from the standard Ubuntu repositories to illustrate this use of sudo: Once you’ve provided your password the apt program will print out quite a few lines of text to tell you what it’s doing. The standard pager of old was called more, because it puts a line of text at the bottom of each page that says “–More–” to indicate that you haven’t read everything yet. Open Ubuntu Terminal Window, the command line interface. Type in echo followed by some texts within parentheses to find out for yourself. Try taking a brief look at the pages for some of the commands you’ve already encountered: man ls, man cp, man rmdir and so on. The key to this approach is a command called sudo (as in “switch user and do this command”). Unless you know exactly what the file is doing, you’re opening up a hole through which malware could potentially be installed onto your system. Now we know how to move, copy and rename files and directories. There are lots of different ways to install software on Linux systems. Knowledge of the commands associated with it and also how to string them together will make your life with Ubuntu much easier. It might be hidden away in a submenu or you might have to search for it from within your launcher, but it’s likely to be there somewhere. The name of the current logged on user will be displayed. One important concept to understand is that the shell has a notion of a default location in which any file operations will take place. Checking your Ubuntu version From the lsb_release terminal command The lsb_release command gives LSB (Linux Standard Base) and distribution-specific information on the CLI. You shouldn’t usually need to deal with hidden files, but occasionally instructions might require you to cd into .config, or edit some file whose name starts with a dot. Give it a try to see what happens, but to avoid typing the commands again you can use the Up Arrow and Down Arrow keys to move back and forth through the history of commands you’ve used. Instead it deletes them totally, utterly and irrevocably. If you run ls you’ll see that most of the folders have gone, but folder_6 is still hanging around. As you might have guessed, this capability also means that you need to escape file names with ? The command line is one of the most powerful tools available for use with Ubuntu, and indeed Linux. Obviously, therefore, any programs that ran on the mainframe had to produce text as an output and accept text as an input. If you pass more than two arguments, the last one is taken to be the destination directory and the others are considered to be files (or directories) to move. As any Linux user knows, it’s the command line terminal where the magic happens. On GUI Desktop of Ubuntu, the shortcut to open the command terminal is Ctrl+Alt+T Command to power off Ubuntu If you want to shut down your system immediately, then simply type: Options are used to modify the way in which a command operates, allowing a single command to behave in a variety of different ways. This also works on directories, giving us a way to sort out those difficult ones with spaces in the name that we created earlier. Note that the spaces around the pipe character aren’t important, we’ve used them for clarity, but the following command works just as well, this time for telling us how many items are in the /etc directory: Phew! You will use it whenever you want to see everything that is in … Let’s begin by putting our combined.txt file into our dir1 directory, using the mv (move) command: You can confirm that the job has been done by using ls to see that it’s missing from the working directory, then cd dir1 to change into dir1, ls to see that it’s in there, then cd .. to move the working directory back again. We can use the cat command to look at its content: Okay, so it’s not exactly what was displayed on the screen previously, but it contains all the same data, and it’s in a more useful format for further processing. Let’s give it a go: You probably didn’t even need to type that one in to guess what would happen: two new folders, one called another and the other called folder. When using su your entire terminal session is switched to the other user. Good naming practice In practice you’ll still most likely use a graphical program when you want to move, rename or delete one or two files, but knowing how to do this using the command line can be useful for bulk changes, or when the files are spread amongst different folders. We can finally complete our task of counting the unique lines in the file: As you can see, the ability to pipe data from one command to another, building up long chains to manipulate your data, is a powerful tool, as well as reducing the need for temporary files, and saving you a lot of typing. In order to see the whole file we now need to use a different program, called a pager (because it displays your file one “page” at a time). Yes, the developers have set up the launcher with all the most common synonyms, so you should have no problems finding it. With what we now know about paths, that’s no problem either: Notice how our mv command let us move the file from one directory into another, even though our working directory is something completely different. Directoryname − This is the optional directory name that can be specified along with the ls command. Depending on your Linux system the colours may not be the same, and the text will likely say something different, but the general layout of a window with a large (mostly empty) text area should be similar. To avoid accidentally trampling over any of your real files, we’re going to start by creating a new directory, well away from your home folder, which will serve as a safer environment in which to experiment: Notice the use of an absolute path, to make sure that we create the tutorial directory inside /tmp. The single character form allows for multiple options to be combined, though not all commands will accept that. Let’s wander around the file system a little, and keep an eye on the prompt as you do so: You must be bored with just moving around the file system by now, but a good understanding of absolute and relative paths will be invaluable as we move on to create some new folders and files! By encouraging use of su the aim was to persuade administrators to spend most of their time using a normal account, only switch to the superuser account when they needed to, and then use the logout command (or Ctrl-D shortcut) as soon as possible to return to their user-level account. Switching to Ubuntu Budgie Desktop Environment for Chrome Remote Desktop The path to Budgie is /usr/bin/budgie-desktop so to switch to it you can run: sudo bash -c 'echo "exec /etc/X11/Xsession /usr/bin/budgie-desktop" > /etc/chrome-remote-desktop-session' Update Ubuntu Server in the Command Line. Surely that can’t be right? But it’s still not worth taking the risk, in case the account has been enabled without you realising. When used with no arguments it assumes you want to change to the root user (hence the first interpretation of the name), but you can pass a username to it in order to switch to a specific user account (the second interpretation). But we can use another path shortcut to avoid changing directory at all. Using the tilde character ("~") at the start of your path similarly means “starting from my home directory”. When running a command like this, the user is prompted for their own password, which is then cached for a period of time (defaulting to 15 minutes), so if they need to run multiple superuser-level commands they don’t keep getting continually asked to type it in. You’ll see an error saying “No such file or directory” before you even get to run the last pwd. Introduction. Most command line tools come with a brief (and sometimes not-so-brief) instruction manual, accessed through the man (manual) command. In this chapter, we will go through some of the popular command line’s used in Ubuntu. No matter what your current working directory is, they’ll have the same effect. I installed Ubuntu and the resolution of the desktop is so big that it only shows about 50% of the screen, but is shows up normal while using command line. The command “df” shows the amount of disk space used and disk space available on every file system … For example, a software publisher’s site might ask you to download a file and change its permissions, then use sudo to run it. An asterisk ("*") can be used to indicate “zero or more characters”. This time the file will be displayed without prompting you for a password, as it’s still in the cache. Open command terminal or if you are using a server with CLI interface then you are already there. There was no mouse, no fancy graphics, not even any choice of colour. Or will it replace it entirely? When adding a new user there is an option to create them as an administrator, in which case they will also be able to run superuser commands with sudo. That’s quite a few files. sed is a simple “inline editor.” Like piping text to grep, you can pipe data directly to sed, and … Increasingly, Ubuntu is making use of “snaps”, a new package format which offers some security improvements by more closely confining programs to stop them accessing parts of the system they don’t need to. In this section we’re going to create some real files to work with. How to install an app/program in Ubuntu via command line: You might have to type sudo before some of these Ubuntu commands. This is its working directory. It’s only polite to leave your computer in the same state that we found it in, so as a final step, let’s remove the experimental area that we were using earlier, then double-check that it’s actually gone: As a last step, let’s close the terminal. Finally, type the new character in place, and press Enter or Return to run the command once you’re finished. Fortunately the command line doesn’t limit you to a single pipe at a time, so we can continue to chain as many commands as we need: That line probably resulted in a count that’s pretty close to the total number of lines in the file, if not exactly the same. The question, then, is how to rearrange the lines in our file so that duplicate entries are on adjacent lines. Unix-like systems don’t split up the drives like that. Each of these tasks required its own program or command: one to change directories (cd), another to list their contents (ls), a third to rename or move files (mv), and so on. The superuser, as the name suggests, has more powers than a normal user, so can easily wreak havoc with a badly typed command. But suppose we want to create a directory with a space in the name? Don’t use su Let’s see how you can do that yourself! As you can see from the output current Ubuntu version is Ubuntu 20.04.1 LTS. If you try to create new files or directories, view existing files, or even delete them, the shell will assume you’re looking for them in the current working directory unless you take steps to specify otherwise. How do you kill a process on the Ubuntu operating system using the command line? Commands that don’t need root access, something as mundane as pwd or ls, would be run under the auspices of the superuser, increasing the risk of a bug in the program causing major problems.
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