Lab 3 - Common System Utilities

Objectives¶

After completing this lab, you will be able to

• Use the common system utilities found on most Linux Systems

Estimated time to complete this lab: 70 minutes

Common system utilities found on Linux systems¶

What is a System Utility?¶

In a Linux environment, system utilities are programs and commands that allow you to manage, monitor, and optimize the operation of the operating system. These tools are essential for system administrators, developers, and advanced users, as they simplify tasks such as file management, process control, network configuration, and much more.

Unlike graphical interfaces, many utilities are accessible via the command line, offering greater flexibility, automation, and control over the system.

The exercises in this lab cover the usage of some basic system utilities that users and administrators alike need to be familiar with. Most of the commands are used in navigating and manipulating the file system. The file system is made up of files and directories.

The exercises will cover the usage of –pwd, cd, ls, rm, mv, ftp, cp, touch, mkdir, file, cat, find, and locate utilities.

Exercises¶

1. File system navigation with cd¶

The cd command (short for Change Directory) is one of the most commonly used commands in Linux and Unix-like systems. It allows you to move between directories in the file system, enabling users to navigate between folders and access the files within them.
The cd command is essential for working in the Linux shell, as it allows you to explore and organize the file system efficiently.

How to use cd¶

1. Log in to the computer as root

2. Change from your current directory to the /etc directory.

   [root@localhost root]# cd /etc
   

3. Note that your prompt has changed from “[root@localhost root]# ” to : “[root@localhost etc]# “

4. Change to the /usr/local/ directory

   [root@localhost etc]# cd /usr/local
   
   [root@localhost local]#
   

   Question

   What has changed about your prompt?

5. Change back to root’s home directory

   [root@localhost local]# cd /root
   

6. Change to the /usr/local/ directory again. Type:

   [root@localhost root]# cd /usr/local
   

7. To change to the parent directory of the local directory type cd ..

   [root@localhost local]# cd ..
   

   Question

   What is the parent directory of the /usr/local/ directory?

8. To quickly change back to root’s home directory type cd without any argument.

   [root@localhost usr]# cd
   [root@localhost root]#
   

2. Display the path with pwd¶

The pwd (Present Working Directory) command shows the user the absolute path of the current directory within the file system. It is used to identify the current location when working in a terminal and you want to know exactly where you are.
This command is essential for navigating the file system, especially when working with complex paths or automated scripts.

How to use pwd¶

1. To find out your current working directory type:

   [root@localhost root]# pwd
   /root
   

2. Change your directory to the /usr/local/ directory using the cd command:

   [root@localhost root]# cd /usr/local
   

3. Use pwd to find your present working directory:

   [root@localhost local]# pwd
   /usr/local
   

4. Return to root’s home directory:

   [root@localhost root]# cd
   

3. Create folders with mkdir¶

The mkdir (Make Directory) command allows you to create new directories (folders) within the file system. In this exercise, you will create two folders named folder1 and folder2.

How to use mkdir¶

1. Create the first directory called folder1

   [root@localhost root]# mkdir folder1
   

2. Create a second directory called folder2

   [root@localhost root]# mkdir folder2
   

3. Now change your working directory to the folder1 directory you created above.

   [root@localhost root]# cd folder1
   

4. Display your current working directory.

   [root@localhost folder1]# pwd
   /root/folder1
   

   Question

   Without leaving your present directory, change to the folder2 directory. What is the command to do this?

5. Return to root’s home directory.

4. Modify file metadata with touch¶

The touch command is a tool that allows you to create new empty files or modify the access/modification dates of existing files, as well as advanced uses in scripting and automation. The name touch comes from the idea of “touching” the file's metadata without necessarily modifying its content.
The files file11, file12, file21, and file22 will be created in the folders created above.

How to use touch¶

1. Change directory i.e. cd to folder1 and create file11:

   [root@localhost folder1]# touch file11
   

2. While still in folder1 create file12:

   [root@localhost folder1]# touch file12
   

3. Now return to root’s home directory.

4. cd to folder2 and create file21 and file22

   [root@localhost folder2]# touch file21 file22
   

5. Return to root’s home directory.

5. List directories with ls¶

The ls (List) command is one of the most fundamental and widely used commands in Linux and Unix-like systems. It allows you to view the contents of a directory, displaying files and subdirectories with various formatting and sorting options.

To use ls¶

1. Type ls in root’s home directory:

   [root@localhost root]# ls
   

   Question

   List the contents of the directory

2. Change to the folder1 directory

3. List the contents of folder1 directory. Type ls

   [root@localhost folder1]# ls
   file11  file12
   

4. Change to the folder2 directory and list its contents here:

5. Change back to your home directory and list all the hidden files and folders:

   [root@localhost folder2]# cd
   [root@localhost root]# ls –a
   ..  .bash_history  .bash_logout  .bash_profile  .bashrc  folder1  folder2  .gtkrc  .kde   screenrc
   

6. To obtain a long or detailed list of all the files and folders in your home directory type:

   [root@localhost root]# ls –al
   total 44
   drwx------    5 root    root        4096 May  8 10:15 .
   drwxr-xr-x    8 root     root         4096 May  8 09:44 ..
   -rw-------    1 root    root          43 May  8 09:48 .bash_history
   -rw-r--r--    1 root    root          24 May  8 09:44 .bash_logout
   -rw-r--r--    1 root    root         191 May  8 09:44 .bash_profile
   -rw-r--r--    1 root    root         124 May  8 09:44 .bashrc
   drwxrwxr-x    2 root    root        4096 May  8 10:17 folder1
   drwxrwxr-x    2 root    root        4096 May  8 10:18 folder2
   ………………………..
   

6. Moving files with mv¶

The mv (Move) command provides a tool for managing files in the system. Its main function is to move or rename files and directories within the file system. This command is particularly useful for reorganizing the directory structure, performing batch operations on groups of files, and managing backups efficiently.

How too use mv¶

1. Change directory to the folder1 directory and list its contents:

   [root@localhost root]# cd folder1
   [root@localhost folder1] ls
   file11  file12
   

2. You will rename file11 and file12 in the folder1 directory to temp_file11 and temp_file12 respectively:

   [root@localhost folder1]# mv file11 temp_file11
   

3. List the contents of folder1 again.

   [root@localhost folder1]# ls
   

   Question

   Write down the contents:

4. Rename the file12 to temp_file12:

   [root@localhost folder1]# mv file12 temp_file12
   

5. Without changing directory rename the file21 and file22 in folder2 to temp_file21 and temp_file22 respectively:

   [root@localhost folder1]# mv /root/folder2/file21 /root/folder2/temp_file21
   [root@localhost folder1]# mv /root/folder2/file22 /root/folder2/temp_file22
   

6. Without changing your current directory list the contents of folder2.

   Question

   What is the command to do this? Also list the output of the command?

7. Copying files with cp¶

The cp (Copy) command allows you to duplicate files and directories from one location to another in the file system, keeping the original file intact. Its ease of use and versatility make it indispensable for both everyday operations and more complex system administration tasks.
Among the most useful features of the cp command is the ability to preserve the original attributes of files during copying, including permissions, timestamps, and owner information. This feature is particularly important when working with configuration files or when certain document properties need to be kept intact.

How to use cp¶

1. Change your directory to the folder2 directory.

2. Copy the contents of folder2 (temp_file21 and temp_file22) to folder1:

   [root@localhost folder2]# cp temp_file21 temp_file22 ../folder1
   

3. List the contents of folder1.

   [root@localhost folder2]# ls ../folder1
   temp_file11  temp_file12  temp_file21  temp_file22
   

4. List the contents of folder2. Note that the original copies of temp_file21 and temp_file22 remain in folder2.

   [root@localhost folder2]# ls
   temp_file21  temp_file22
   

8. Determining the file type with file¶

The file command is a diagnostic tool that allows you to determine the type of a file by analyzing its contents. Unlike file extensions, which can be modified or misleading, this command examines the actual structure of the data to accurately identify its nature.
One of the most important features of the file command is its ability to distinguish between different types of text files, identifying, for example, shell scripts, source code in various programming languages, XML or JSON files. For binary files, it can recognize executables, shared libraries, images in various formats, and many other types of structured data.

How to use file¶

1. Change back to your home directory.

2. To see if folder1 is a file or directory; type:

   [root@localhost root]# file folder1
   folder1: directory
   

3. Change to the folder1 directory

4. Use the file utility to determine the file type for temp_file11:

   [root@localhost folder1]# file temp_file11
   temp_file11: empty
   

5. Use the file utility to find out the file type for all the files in the folder1 directory. List here:

6. Change directory to the /etc directory:

   [root@localhost folder1]# cd /etc
   

7. Use the file utility to find out the file type for the passwd file.

   [root@localhost etc]# file passwd
   

   Question

   What type of file is it?

9. List and concatenate files with cat¶

The cat command (short for Concatenate) is an essential tool for managing text files in Linux. Its main function is to display the contents of one or more files directly in the terminal, but it can also be used to create, merge, or copy files.
The cat command is particularly useful in combination with other tools (such as grep or more) for processing or filtering text directly from the terminal. Despite its simplicity, it is one of the most widely used commands for quick file manipulation.
You will use cat along with the redirection symbol “>” to create a file.

To use cat to create a file¶

1. Change directory to the /root/folder1 directory

2. Create a new text file called first.txt

   [root@localhost folder1]# cat > first.txt
   

3. Type in the phrase below at the blank prompt and press Enter.

   This is a line from first.txt !!
   

4. Press the Ctrl+C simultaneously.

5. Type cat first.txt to read the text you just typed in:

   [root@localhost folder1]# cat first.txt
   This is a line from first.txt !!
   

6. Create another file called second.txt using cat. Type the following text into the file – “This is a line from second.txt !!”

   Question

   What is the command to do this?

To use cat to concatenate files together¶

1. You will concatenate the files first.txt and second.txt. Type:

   [root@localhost folder1]# cat first.txt second.txt
   

   Question

   What is your output?

10. Transferring files with ftp¶

The ftp (File Transfer Protocol) command is a command line tool for transferring files between remote and local systems. Although it has been partially replaced by more modern and secure protocols such as SFTP and SCP, it remains useful in legacy contexts or with servers that only support FTP.
FTP transmits data in clear text, including credentials and content, so it is not recommended for sensitive transfers.
Although FTP is still used in some environments, encrypted protocols are preferable for secure operations.
In this exercise you will learn how to log on anonymously to an FTP server and download a file from the server using an ftp client program.

How to use ftp¶

1. Log on to your machine as root

2. Change directory to the /usr/local/src/ directory

3. Create a new directory called downloads under the /usr/local/src/ directory.

   Question

   What is the command to do this?

4. Change directory to the newly created downloads directory

   [root@localhost src]# cd downloads
   

5. Type ftp to launch your ftp client:

   [root@localhost downloads]# ftp
   ftp>
   

6. To connect to the FTP server type:

   ftp> open  < server-address>    (Obtain the <server-address> from your instructor)
   ………
   220 localhost.localdomain FTP server (Version wu-2.6.2-5) ready.
   ………..
   

7. Log in as an anonymous user. Type “anonymous” at the prompt:

   Name (10.4.51.29:root):  anonymous
   

8. Type in any e-mail address at the password prompt and press Enter

   Password: ***************
   230 Guest login ok, access restrictions apply.
   Remote system type is UNIX.
   Using binary mode to transfer files.
   ftp>
   

9. Change to binary mode. Type:

   ftp> binary
   

   Question

   What is the output of the binary command and what is the "binary mode"?

10. List the current directories on the ftp server. Type ls at the ftp prompt:

    ftp> ls
    227 Entering Passive Mode (10,0,4,5,16,103).
    125 Data connection already open; Transfer starting.
    11-23-43  10:23PM       <DIR>          images
    11-02-43  02:20PM       <DIR>          pub
    226 Transfer complete.
    

11. Change directory to the pub directory. Type:

    ftp> cd  pub
    

12. Use the ls command to list the files and directories in the pub directory

    Question

    How many files and directories are in there now?

13. Download the file called “hello-2.1.1.tar.gz” to your local directory. Type “yes” at the prompt.

    ftp> mget hello-2.1.1.tar.gz
    mget hello-2.1.1.tar.gz? yes
    227 Entering Passive Mode (10,0,4,5,16,252).
    125 Data connection already open; Transfer starting.
    226 Transfer complete.
    389363 bytes received in 0.0745 secs (5.1e+03 Kbytes/sec)
    

14. Log off the FTP server and exit your ftp client. Type:

    ftp> bye
    

15. You will be thrown back into your local shell.

16. Ensure you are still in the local machine's downloads directory on your local machine.

    Question

    List the files in the downloads folder.

11. Using redirection¶

Most of the utilities and commands you use in Linux send their output to the screen. The screen is called the standard output (stdout). Redirection allows you to send the output somewhere else – maybe a file.

Every program started on a Linux system has three open file descriptors, stdin (0), stdout (1) and stderr (2). You may redirect or "pipe" them individually. The redirection symbols are > and <.

How to use redirection¶

1. Ensure you are still in the folder1 directory.

2. You will use output redirection to redirect the output to an ls (list) command to a text file called myredirects:

   [root@localhost folder1]# ls > myredirects
   

3. Examine the contents of the new file (myredirects) created in the folder1 directory.

   [root@localhost folder1] # cat myredirects
   temp_file11  temp_file12  temp_file21  temp_file22 myredirects
   

4. Now you will redirect the output of the file command into that same file. You want to find out the file type for the temp_file11 in the folder1 directory and send the output to your myredirects file:

   [root@localhost folder1]# file temp_file11 > myredirects
   

5. Examine the contents of the myredirects file.

   Question

   It has changed. What happened?

6. If you want to prevent what happened above from happening you will use the double redirection symbol >+>. This will append (add) the new output to the file instead of replacing it. Try it:

   [root@localhost folder1]# ls >> myredirects
   

7. Now examine the contents of the file myredirects again using cat.

   Question

   Write down its contents here:

Using redirection to suppress the output of a command¶

You will be using the concepts covered here a lot in Linux, so please pay particular attention to it. It can be a bit tricky.

There will be times when you do not want the user to see the output of a command - perhaps an error message. This will usually be because strange error messages often scare regular users. In this exercise you will send the output of your commands to the null device ( /dev/null/ ). The null device is like a “bit bucket”. Anything you place inside disappears forever. You can also send (or redirect) regular command output to the null device.

Use the guidelines below:

1. Ensure you are still in the folder1 directory. Use the long listing option of the ls command on temp_file11:

   [root@localhost folder1]# ls –l temp_file11
   -rw-r--r-- 1 root   root    0   Jul 26 18:26    temp_file11
   

2. You will redirect the output of the same command above (ls –l temp_file11) to the null device.

   [root@localhost folder1]# ls –l temp_file11 > /dev/null
   

   You should have no output.

3. Now if you accidentally mis-spell the name of the file whose information you want to see; You will get:

   [root@localhost folder1]# ls –l te_file1
   ls: te_file1: No such file or directory
   

   The above is the result of the type of error the ls command was programmed to give.

4. Run the same command as the above with an incorrect spelling of the file name and redirect it to /dev/null

   [root@localhost folder1]# ls -l te_file1 > /dev/null
   ls: te_file1: No such file or directory
   

   Question

   What happened here? How come the output still showed up on the screen (stdout)?

5. For various reasons you may want to suppress error messages such as the one above. To do this type:

   [root@localhost folder1]# ls –l te_file1 > /dev/null 2>&1
   

   You will not get any output. This time the standard output as well as the standard error is suppressed.

   The order of redirection is IMPORTANT!!

   Redirection is read from left to right on the command line. The left-most part of the redirection symbol - > will send the standard output (stdout) to /dev/null. Then the right-most part of the redirection - 2>&1 will duplicate the standard error (2) to the standard output (1).

   Hence the above command can be read as: redirect stdout(1) to “/dev/null” and then copy stderr (2) to stdout

6. To further demonstrate the importance of the order of redirection; Try:

   [root@localhost folder1]# ls –l tem_file 2>&1 > order.txt
   

   Use the cat command to examine the contents of the file “order.txt”

   The left-most part – 2>&1 will copy the standard error to the standard output. Then, the right-most part of the above – > order.txt redirects stdout to the file order.txt.

7. Try this variation of the above step:

   [root@localhost folder1]# ls –l hgh_ghz 2> order2.txt > order2.txt
   

   Question

   Examine the file “order2.txt” and explain what happened?

8. To send the standard output and standard error to separate files; Type:

   [root@localhost folder1]# ls –l tep_f > standard_out 2> standard_err
   

   Question

   Two new files were created. What are the names of the files and what are their contents?

9. You can similarly redirect both stdout and stderr to the same file by using:

   [root@localhost folder1]# ls –l te_fil &> standard_both
   

12. Deleting files with rm¶

The rm (Remove) command allows you to permanently delete one or more files, directories, and their contents, with no possibility of recovery unless you use external recovery solutions. It is a powerful command but potentially dangerous if used improperly, as it operates irreversibly. For this reason, it is important to use it with caution, always checking the paths and file names before performing the operation.
You are going to use rm to delete some of the files you created in the earlier exercises.

How to use rm¶

1. While still in the folder1 directory, delete the file standard_err. Type y at the confirmation prompt:

   [root@localhost folder1]# rm standard_err
   rm: remove `standard_err'? y
   

2. Delete the standard_out file. To prevent being prompted for confirmation before deleting a file use the –f option with the rm command:

   [root@localhost folder1]# rm -f standard_out
   

3. Change back to your home directory (/root) and delete the folder2 directory. To use rm to delete a folder you need to use the –r switch:

   [root@localhost root]# rm -r folder2
   rm: descend into directory 'folder2'? y
   rm: remove 'folder2/temp_file21'? y
   rm: remove 'folder2/temp_file22'? y
   rm: remove directory 'folder2'? y
   

   Question

   You were again prompted to confirm the removal of each file in the directory and the directory itself. What option will you use with the rm –r command to prevent this?

13. Learning vi¶

The vi editor is one of the most powerful and widely used text editors available on Linux and Unix-like systems. It is an essential tool for system administrators and developers thanks to its efficiency and versatility. Unlike many modern editors, vi operates primarily in text mode, offering quick commands and key combinations that allow you to edit files with extreme precision and speed.

Its learning curve may be steep at first, but once you master the basic features, it becomes an indispensable tool for editing configuration files, scripts, and source code directly from the terminal.

vi is a big fat monster that can do almost everything - including make your coffee or cocoa!!

Instead of trying to teach you vi, this exercise will point you to a tool that can better familiarize you with vi. Please take the time to go through the online vi (more precisely vim) tutorial. Just follow the instructions.

To learn vi¶

1. While logged into the system, type:

   [root@localhost root]# vimtutor

14. Searching files with find and locate¶

This exercise will discuss two of the most popular utilities used for searching for files and directories on the file system. They are the find command and the locate commands.

find¶

The find command allows you to search for files and directories within the filesystem based on a wide range of criteria, such as name, type, size, modification date, permissions, and much more. Its ability to perform actions on the results found, such as deleting, moving, or processing files, makes it an indispensable tool for system administrators and advanced users.

The general syntax for find is:

find   [path]    [options]   [criterion]    [action]

If you do not specify any directory or path, find will search the current directory. If you do not specify a criterion, this is equivalent to "true", thus all files will be found. The find utility has many options for doing just about any type of search for a file. Only a few of the options, criteria and actions are listed below.

How to use find¶

1. Ensure you are in your home directory.

2. You will use find to display all the files in your current directory (pwd). Type:

   [root@localhost root]# find
   ………..
   ./.bash_profile
   ./.bashrc
   ./.cshrc
   ./.tcshrc
   ./.viminfo
   ./folder1
   ./folder1/first.txt
   …………
   

   Your output shows the default behavior of find when used without any option.
   It displays all the files and directories (including hidden files) in the working directory recursively.

3. Now use find to find only the directories in your pwd. Type:

   [root@localhost root]# find -type d
   ./folder1
   ./folder2
   ………
   

   Questions

   From the above command find –type d; what is the “option”, what is the “path”, what is the “criterion” and finally what is the “action”?

4. Next you will search for all the files on your system that end with the suffix “.txt”:

   [root@localhost root]# find / -maxdepth 3 -name "*.txt" -print
   /root/folder1/first.txt
   /root/folder1/second.txt
   /root/folder1/order.txt
   /root/folder1/order2.txt
   

   Questions

   Again from the above command, what is the “option”, what is the “path”, what is the “criterion” and finally what is the “action”? (HINT: The action = “-print”)

   The search will only be performed 3 directories deep from the / directory. The asterisk used in the command above is one of the “wild card” characters in Linux.
   The use of wild-cards in Linux is called “globbing”.

5. Use the find command to find all files in your “pwd” that are “smaller” than 200 kilobytes in size. Type:

   [root@localhost root]# find . –size -200k
   

6. Use the find command to find all the files in your pwd that are “larger” than 10 kilobytes and display their “file type” as well. Type:

   [root@localhost root]#  find . –size +10k –exec file "{ }" ";"
   

locate¶

The locate command allows you to search for files and directories within the system. Unlike other commands such as find, which perform a real-time search, locate is based on a precompiled database containing the paths of all files on the system, ensuring almost instant results. This database is usually updated periodically using the updatedb command, managed by a cron job. Thanks to its efficiency, locate is particularly useful for quickly finding files or folders without having to manually scan the entire file system.
However, it is important to remember that the results may not always be up to date if the database has not been recently synchronized with the current state of the system.

How to use locate¶

1. Change to the folder1 directory and create empty files temp1, temp2 and temp3:

   [root@localhost root]# cd folder1; touch temp1 temp2 temp3
   [root@localhost folder1]#
   

   The semicolon (;) used in the command above, allows you to issue multiple commands on a single line!!

2. Use locate to search for all the files in your pwd that have the suffix “temp”

   [root@localhost folder1]# locate temp*
   /root/folder1/temp_file11
   /root/folder1/temp_file12
   /root/folder1/temp_file21
   /root/folder1/temp_file22
   

   Note that the three files you created in step 1 were NOT found.

3. You will force an update of the database using updatedb to enable it to take cognizance of all newly created files. Type:

   [root@localhost folder1]# updatedb
   

4. Now try the search again. Type:

   [root@localhost folder1]# locate temp
   

   Question

   What happened this time?

5. All done with Lab 3.

Author: Wale Soyinka

Contributors: Steven Spencer, Ganna Zhyrnova, Franco Colussi