We’ve compiled a list of methods you can use to locate missing files in Linux. As always, we include tools for both more experienced users and beginners, and we hope that these suggestions allow you to avoid the traumatic loss of important data!

Using the grep command to find a file by its contents

Grep has been part of Unix for so long that you will often see the term used as a verb in Linux discussions online (it’s generally synonymous with “search locally”). It can be thought of as the ultimate “pattern recognition tool”. However, Grep should only be used to search for the contents of a file rather than finding items using their filename.

Now, let’s look at how grep is actually used. Let’s say you had a file in your ~/Documents directory called ‘Give.txt’. The contents of the file are as follows:

What's real can't die
You only get what you give
You're gonna get what you give
Don't give up
Just don't be afraid to leave

Of course, these are the lyrics to a famous song by New Radicals. It’s an excellent example in this case, as it highlights how useful grep is and a few of its behaviors that might appear idiosyncratic at first to new users.

From our Documents directory, we’re going to execute the following command:

grep you give.txt

Press return, and you’ll see that it returns every line with the word “you” in it:

Now, let’s try another command (remember to include the escaped apostrophe):

grep don't give.txt

And here is our result:

As you can see, the fifth line was identified; however, because grep is case-sensitive by default, the fourth line (“Don’t give up”) was not returned.

Now, we’ll use the “-i” flag to turn off case-sensitivity in our following query (I’ve also now used quotations to avoid relying on the backslash character this time):

grep -i "don't" give.txt

This time, we can see that every instance of the word – regardless of case – is brought back. If you use the “-i” flag when searching for “you”, you’ll also notice that it now highlights the capitalized appearances of the word as well:

Using the find command to find a file by its name

While grep allows users to query the contents of files on their computer, the find tool provides an efficient way to locate items based on their actual filename.

The most basic use of the find command is as follows:

find .

The period (‘.’) tells the command to return every file and subdirectory found if we search from the present working directory. Essentially, all this is is a good starting point.

However, there are a variety of additional arguments which allow us to get a lot more specific with how we use the find tool. For example, the following command will return all subdirectories from the present location (with ‘d’ standing for “directories”):

find . -type d

Alternatively, we can return only files by typing:

find . -type f

The find command becomes especially useful for locating misplaced files when switching out the “-type” option with “-name”. For example, we can return all ePub files (either in the current directory or within its subdirectories) by using:

find . -name "*.epub"

Or, we can find all ePub files with the word “great” in the name by typing:

find . -name "*great*epub"

And, as with the grep tool, we can choose to make our query case-insensitive:

find . -iname "*great*epub"

And, if we want to narrow it down even further, we can combine options too:

find . -type f -iname "*GrEat*"

The above example is slightly redundant, as we only have files with the word ‘great’ in their title. However, if the ~/Downloads folder also had a subdirectory called “Great Expectations”, it would be omitted from our results as we have specifically included the ‘-type f’ option.

Find files using Catfish

For those who prefer not to use the command line, you can use a GTK3 application called Catfish. This can be installed from the software repository of your Linux distribution by typing:

sudo apt-get install catfish -y

Other popular choices for Linux users who prefer to use GUI to locate files include fsearch, Cerebro, and Terrier.

Catfish can provide complex searches (based on criteria like date of modification, file type, and so on). While it’s not quite as powerful as grep or find, it should suit most users fine.

The post How to Find a File in Linux appeared first on Coding Campus.

Check CentOS Using RPM (Easiest)

The RPM Package Manager provides the quickest and easiest way to find out which version of CentOS is running.

1. From the home screen, click ‘Activities’ in the top left-hand corner.

   

2. Then, type ‘terminal’ into the search box which appears. Now, click the terminal button.

   

3. In the terminal window, enter the following command:

rpm -q centos-linux-release

Then hit enter.

As you can see, the exact version of CentOS (including the major release number, as well as the revision).

Check CentOS Version Using Your Release File

You might not know this, but there’s actually a text file included in your CentOS installation. It’s located in the ‘/etc/’ directory, and it’s very handy for checking your release version.

1. From the home screen, click ‘Activities’ in the top left-hand corner.

   

2. Now, click the Terminal icon which appears on the left-hand sidebar.

   

3. In the window which opens, enter the following command:

cat /etc/centos-release

Then hit enter.

There’s also a way to find out more details about your release, by using the following command instead:

cat /etc/os-release

And hit enter.

As you can see, this command doesn’t provide your exact release number, but it does provide other useful information such as the ‘Platform_ID’ and the ‘Pretty Name’.

Check the ‘Pretty Name’ Using the GUI

If you’re also content just to know which major release of CentOS you’re using, you can do this using the graphical interface. This method might also be useful if – for whatever reason – you can’t use the terminal.

1. Again, click ‘activities’ in the top left-hand corner.

   

2. Then, type ‘version’ into the search box which appears.

   

3. You can now see the release of CentOS you’re currently running. Although less detailed, this method only requires using the GUI.

Bonus Tip: You can click the ‘View Updates’ button in the bottom right-hand area of the above screenshot to begin updating your current installation (if needed).

The post How to Check CentOS Version appeared first on Coding Campus.

grep Command Purpose and Syntax

grep searches for patterns in a file(s). patterns refer to one or more patterns separated by newline characters, and grep prints each line that matches a defined pattern.

# grep [operators...] patterns [file...]

Types of Regular Expressions

There are three main types of Linux regular expressions:

Basic Regular Expressions

A Basic Regular Expression (BRE) is a regular expression consisting of the exact characters of the string to be matched.

Basic Regular Expression Operators

• . — replaces any character
• ^ — matches start of string
• $ — matches end of string
• * — matches up zero or more times the preceding character
• — represent special characters
• () — groups regular expressions
• ? — matches up exactly one character

Basic Regular Expression – Example

In this example, we list all comments in the /etc/adduser.conf file. (Note that the # sign prefaces comments in .conf files).

# grep ^# /etc/adduser.conf

Display all comments (#) in /etc/adduser.conf.

Interval Regular Expressions

An Interval Regular Expression (IRE) is a regular expression that reports the number of characters in a string.

Interval Regular Expression Operators

• {n} — matches the preceding character appearing ‘n’ times exactly
• {n,m} — matches the preceding character appearing ‘n’ times but not more than m
• {n, } — matches the preceding character only when it appears ‘n’ times or more

Interval Regular Expression – Example

In this example, we’ll find all content in the /etc/adduser.conf that contains the ‘l‘ character exactly two times consecutively.

# grep -E l{2} /etc/adduser.conf

Extended Regular Expressions

An Extended Regular Expression (ERE) is a regular expression that contains more than one expression.

Extended Regular Expressions Operators

The extended regular expression contains more than one expression.

• +  — matches one or more occurrences of the previous character
• ? — matches zero or one occurrence of the previous character

Extended Regular Expression – Example

In this example, we’ll search /etc/adduser.conf where character ‘t‘ precedes character ‘a.’

# grep "t+a" /etc/adduser.con

The post Regular Expressions in grep (Regex) (With Examples) appeared first on Coding Campus.

Types of Symbolic Links

Before we delve into creating symbolic links, let’s first explore the two types of symbolic links — soft links and hard links.

Soft Links

Soft links point to the location or path of the original file or directory. Soft links are most often used when you want to quickly access a without typing the entire location. It’s also important to know if a symbolic link file is deleted, the original file or directory remains. However, the symbolic link will no longer work if the original file is moved or deleted.

Hard Links

Hard links, in contrast, point to data physically written to disks. They point to an inode or reference file that points to the data’s location. In short, this is much like creating a copy of the file in that you are creating a second filename that refers to the inode data of the original file. Hard links are not considered symbolic links in the purest sense of the word and are not often used by average Linux users.

ln Command Purpose and Syntax

The ln command allows you to create a hard or soft symbolic link. The syntax for the ln command is:

# ln [options] [file/directory] ...  [link name]

Create a Symbolic Link to a File

Let’s create a symbolic link to a file. In our first example, we will create a link on our desktop, /home/mtravisrose/Desktop/blue-link.txt, to a file in the home directory, /home/mtravisrose/blue.txt.

Open your terminal and enter:

# ln -sv blue.txt /home/mtravisrose/Desktop/blue-link.txt

Note that blue-link.txt symbolic link was successfully created. The ‘l‘ at the beginning of blue-link.txt – > blue.txt file listing denotes that the file is a symbolic link file.

Create a Symbolic Link to a Directory

Let’s create a symbolic link to a file. In our first example, we’re going to create a link on our home directory, /home/mtravisrose/main-ssh-directory, to a directory on our system, /ssh.

Open your terminal and enter:

# ln -s /ssh main-ssh-directory

Note that main-ssh-directory symbolic link was successfully created. The ‘l‘ at the beginning of main-ssh-directory – > /ssh directory listing denotes that the file is a symbolic link file.

Create a Hard Link

Creating hard links in Linux is almost identical to creating soft links. In our example, we’re going to create a hard link, red.hard, from a file, red.txt.

Open your terminal and enter:

# ln red.txt red.hard

You can see that the hard link, red.hard, was created from the file, red.txt. Note that the inode is the same for both files.

Remove or ‘Unlink’ a Symbolic Link

Soft links can be removed in two separate ways: the rm command and the unlink command.

Remove a Symbolic Link with rm

# rm /home/mtravisrose/Desktop/blue-link.txt

Remove a Symbolic Link with unlink

# unlink main-ssh-directory

It’s important to note that only the symbolic link has been removed with both examples, and the actual file or directory remains.

The rm command does not work on hard links. You must use unlink.

The post ln Command in Linux – Create Symbolic Links (With Examples) appeared first on Coding Campus.

This article will show you how to find your Ubuntu version using the GUI or command line.

Note: We’re using Ubuntu LTS 22.04, codenamed Jammy Jellyfish, for this guide.

Check Ubuntu Version via the GUI

Left-click your mouse in the upper-right-hand corner of your screen. Select Settings.

You’ll see your Ubuntu version and a slew of other system-related info in the About window.

Check Ubuntu Version via the Command Line

The examples below show you how to check your Ubuntu version from the command line. Open your terminal and run these commands.

Check Ubuntu Version with hostnamectl

# hostnamectl

Check Ubuntu Version with /etc/lsb-release

# cat /etc/lsb-release

Check Ubuntu Version with lsb_release -a

# lsb_release -a

Check Ubuntu Version with /etc/os-release

# cat /etc/os-release

Check Ubuntu Version with /etc/issue

# cat /etc/issue

Check Ubuntu Version with neofetch

Neofetch is a FOSS command-line utility to ‘fetch’ system information.

First, you must install neofetch.

Open your terminal and enter:

# apt install neofetch

Next, we run neofetch.

# neofetch

You’re presented with a ‘pretty’ display of system-related information, including the OS version.

The post How to Check Ubuntu Version appeared first on Coding Campus.

Note: Linux commands featured in this article are distro-independent, meaning they will work on any Linux distro.

df Command Syntax

The df command displays the amount of free space on the file system containing each file name. If no filename is provided, the free space on all mounted file systems is displayed. The syntax of the df command is as follows.

# df [option] [file]

df Columns

These are the columns usually displayed with the df command.

• File System – name of the disk partition.
• Size – total size of the file system.
• Used – total amount of space allocated to existing files on the file system.
• Available – total amount of space available on the file system.
• Percentage Used – percentage of the available space allocated to files in the file system.
• Mounted On – directory where the file system appears.

df Command Real-Life Scenarios

While many options are available with the df command, we’ll only review those most used by Linux admins and users.

1. If no file name is given, df displays all the space available on all currently mounted file systems:

   # df

   

2. If you specify a particular file directory or a file, df shows the mount information of that file or directory:

   # df filename

   

3. To display all mounted filesystems in human-readable format:

   # df -h

   

4. You can also use options together with the df command. For example, to see your mounted file systems, excluding temporary systems (tmpfs), in human-readable format:

   # df -hx tmpfs

   

The post df Command in Linux (With Examples) appeared first on Coding Campus.

Note: Linux commands featured in this article are distro-independent, meaning they will work on any Linux distro.

Using the touch Command

The touch command is, arguably, the easiest command to create a new empty file.

To create a file with the touch command, from the command line, enter:

# touch newfile.txt

Where newfile.txt is the name of the file to be created.

After we create the command, we can verify its existence with the ls -al command.

# ls -al

Note that you can create multiple files at once using the touch command.

# touch newfile1.txt newfile2.txt newfile3.txt

Using the Redirect Operator (>)

The redirect operator, or right angle bracket, > allows Linux users to create a new empty file quickly.

# > newfile2.txt

Verify the file was created with the ls -al command.

# ls -al

Note that you can use the redirect operator, >, with other commands to create a new file with the results of a command. For example

# ls -al > directorylisting.txt

will create a new file, directorylisting.txt, to output, or ‘redirect’, the directory listing to directorylisting.txt rather than the screen.

Using the cat Command

Although the cat command is primarily used to read and concatenate files, it can also be used to create a new file. To use the cat command to create a new file, enter cat, followed by the redirection operator, >, and the name of the file you want to create. Press <Enter> and type the text you want (press <Enter> for new line). Finally, press <Ctrl><D> to save the file.

# cat > newfile3.txt
This is the first line.
This is the second line.
This is the third line.

Verify that the file was created:

# ls -al

Using the echo Command

The echo command outputs strings passed as arguments to the standard outputs that can be forwarded to a new file using the redirection operator, >. For example:

echo "Let's create a new file." > newfile4.txt

Use the cat command to display the new file’s content.

# cat newfile4.txt

Note that you can use the redirect operator twice, >>, to append text to the file.

echo "We've create a new file!" >> newfile4.txt

Use the cat command to display the new file’s content.

# cat newfile4.txt

Additionally, the echo command with the redirection operator, >, and no text to create an empty file.

# echo > newfile5.txt

Using the printf Command

The printf command works almost identical to the echo command but has added formatting functionality. In this example, we will create a new file, newfile5.txt The file has content. . Use the ls -al command to verify the file, and list the file’s contents.

# printf 'The printf command is similar to the echo command. But has additional formating functions.n' > newfile5.txt
# ls -al
# cat newfile5.txt

Note the “n” in the command above. This signals printf to start a new line.

Like the echo command, with the printf command, you can use double redirect operators, >>, append text to the file.

# printf 'I told you we could add a new line!n' >> newfile5.txt
# cat newfile5.txt

The post How to Create a File in Linux appeared first on Coding Campus.

Note: We’re using Zorin OS 16, an Ubuntu-based distro, for this guide. All Linux commands featured in this article are distro-independent, meaning they will work on any Linux distro, except where otherwise noted.

Renaming Files and Directories from the Linux GUI

Renaming files via the GUI is straightforward in Linux.

1. Navigate to the folder containing the file or directory you wish to rename on your distro’s file manager.

   

2. Select the file you wish to rename. Next, right-click your mouse button and select the Rename option from the menu.

   

3. Enter the desired new filename, and click Rename. In this example, we’re renaming the file orange.txt to purple.txt. (Take care not to rename the file extension if that’s not your intention.)

   

4. You can see the file orange.txt has been renamed to purple.txt.

   

Renaming a folder or directory via the GUI works the same way as renaming a file.

1. Navigate to the folder containing the directory you wish to rename on your Linux distro’s file manager.

   

2. Select the directory you wish to rename. Next, right-click your mouse button and select the Rename option from the menu.

   

3. When presented with the option to rename your directory, enter the desired new directory, and click Rename. In this example, we’re renaming the directory sample_directory to Sample-Directory.

   

4. You can see your directory has been renamed.

   

Renaming files and directories using the mv command

The mv command is Linux’s default command to rename files and directories.

mv Command Syntax

# mv [options] <current-filename> <new filename>

The mv command is used to move or rename a file.

Renaming a file with the mv Command

Open the terminal. Change to the directory containing the file you wish to rename.

# cd techobservatory.com

Use the mv command to rename the file you want to your desired name. In this example, we’re renaming the file orange.txt to purple.txt.

# mv orange.txt purple.txt

List the directory listing to ensure the file has been renamed.

# ls -al

You can also use the -v or verbose option with the mv command to explain what is being done when renaming the file. In this example, we’re renaming the purple.txt file back to orange.txt.

# mv -v purple.txt orange.txt

Renaming a Directory with the mv Command

Open the terminal.

Change to the directory containing the directory you wish to rename

# cd techobservatory.com

Use the mv command to rename the directory you want to your desired directory name. In this example, we’re renaming the directory sample_directory Sample-Directory.

# mv sample_directory Sample-Directory

List the directory to ensure the directory has been renamed.

# ls -al

As the name suggests, the mv command can also move files and directories.

Renaming files and directories using the rename command

One of the significant drawbacks of the mv command to rename files is that, without scripting knowledge, a user can only rename one file at a time. To help combat this problem, Larry Wall, creator of the PERL programming language, created rename, a command-line utility.

Installing the rename utility

Most Linux distros do not come with the rename utility, so it must be installed manually.

To install the rename utility on Debian, Linux Mint, and Ubuntu-based Linux distros, run the following command:

# sudo apt install rename

To install the rename utility on RHEL-based distros like CentOS, Rocky Linux, and Fedora, run:

# sudo yum install rename

To install the rename utility on Arch-based distros:

# sudo pacman -S rename

rename Syntax

# rename [options] [PERLEXPRESSION] [files]

The rename command renames the filenames supplied according to the rule specified in the first argument ([options]). The [PERLEXPRESSION] argument is a Perl expression that is expected to modify the $_ string in Perl for at least some of the filenames specified. If the expression does not change a given filename, it will not be renamed.

Renaming Multiple Files with the rename command

1. Open the terminal.
2. Change to the directory containing the files you wish to rename.

   # cd techobservatory.com

• Use the rename command to rename the files you want to rename. We’re renaming all files with a .txt extension to a .htm extension in this example.

  # rename 's/.txt$/.htm/' *

• List the directory to ensure all files with a .txt extension now have a .htm extension.

  # ls -al

The rename utility is a powerful utility that considerably eases many repetitive renaming tasks for Linux users, such as changing the case of multiple files or renaming file extensions, as in the above example. However, much damage can be done with the rename utility. Care should be taken when using it.

Commands Used in This Guide

• ls – list directory structures.
• mv – rename or move a file or directory.
• rename – rename multiple files.

The post How to Rename Files or Directories in Linux appeared first on Coding Campus.

While you can use these other tools to share files between Windows and Linux machines (e.g. FTP, SFTP, SSH), Samba is preferable as it also allows sharing of printers and makes networking between the Windows and Linux machines transparent. The default port for Samba is port 445.

This article explains how to configure Windows to access Linux, as well as how to configure Linux to access Windows.

We’re using Ubuntu LTS 22.04, codenamed Jammy Jellyfish, an Ubuntu-based distro derived from Debian, and Windows 10 for this guide.

Configure Windows and Enable Sharing

1. Open Settings by clicking on the Start menu and searching for “Settings”.

   

2. Select Network & Internet.

   

3. Select the Network and Sharing Center.

   

4. Select the Change advanced sharing settings option. Check the box next to Turn on network discovery. Select Turn on automatic setup of network connected devices. Next, click Turn on file and print sharing. Click Save Changes.

   

5. Right-click anywhere in your folder and choose New > Folder. In this instance, the shared folder, samba-share (you can choose any name you like), is being created on the desktop.

   

6. Give your folder a name.

   

7. Right-click the newly-created folder and choose Properties. In the General tab, unselect the Read-only attribute. Then, click on the Sharing tab.

   

8. In the Sharing tab, select Share this folder and choose Advanced sharing, which allows you to choose individual permissions.

   

9. enter the share name, samba-share, and select Permissions.

   

10. Select the Permissions button, and add the Samba user, in this case, techobservatory. Give the user Full Control.

    

Configure Linux and Enable Sharing

1. Login to your Linux machine as an admin and launch the terminal.
2.  Since Samba is not generally installed on Linux distros, it must be installed by the Linux user or administrator. To install on Debian- and Ubuntu-based distros:

   # apt install samba smbclient cifs-utils

   

   On RHEL- and CentOS-based distros:

   # rpm -qa samba smbclient cifs-utils

   On Arch-based distros:

   # pacman -Qi samba smbclient cifs-utils

3. Click “Y” when prompted.
4. Setup user as a Samba user. A user can only be added as a Samba user if the user already exists on the Linux distro. In this case, techobservatory. To add the user as a Samba user:

   # smbpasswd -a techobservatory

   

5. Create the directory where you want to mount the share. Note, while we’re using samba-share as the share name,  you can choose any name you like.

   # mkdir /home/techobservatory/samba-share

6. Mount the newly-created share, /home/techobservatory/samba-share.

   # mount.cifs //192.168.1.235/samba-share /home/techobservatory/samba-share -o user=techobservatory

7. Make sure the directory was properly mounted:

   # df

   

8. Next, edit the /etc/samba/smb.conf file. Add the following entries to the end of the file:

   [samba-share]
   path = /home/techobservatory/samba-share
   available = yes
   valid users = techobservatory
   read only = no
   browsable = yes
   public = yes
   writable = yes

   

9. We’ll have to restart the samba service for the changes in the /etc/samba/smb.conf. We’ll also enable it so that it starts every time, as well as check the status.

   # systemctl restart smbd
   
   # systemctl enable smbd
   
   # systemctl status smbd

   

Real-Life Scenario – Access Windows from Linux

1. From the Linux desktop, launch the File Manager.
2. In the address field, enter smb://<IP address>/<Shared folder> (smb://192.168.1.235/samba-share).

   

3. If prompted, enter the username and password.

   

4.  Files and directories can be created, deleted, and modified by the user, techobservatory.

   

Real-Life Scenario – Access Linux from Windows

1. On Windows, launch File Explorer
2. In the address field, enter //<IP address>/<Shared folder> (//192.168.1.135/samba-share).

   

3. The Linux share, samba-share, is accessible from the Windows machine. Files and directories can be created, deleted, and modified by the user, techobservatory.

Commands Used In This Article

• systemctl – control the systemd system and service manager.
  df – report file disk space usage.
  mkdir – make directory.
  mount – mount a filesystem.
  smbpasswd – change a user’s SMB password.
  apt – Debian- and Ubuntu-based command-line interface for the package management system.
  rpm – (Remote Package Manager) package manager to install applications and packages on RHEL- and CentOS-based distros.
  pacman – package manager to install applications on Arch-based systems.

The post How to Transfer or Share Files Between Windows and Linux appeared first on Coding Campus.

Note: We’re using Ubuntu LTS 22.04, codenamed Jammy Jellyfish, an Ubuntu-based distro derived from Debian, for this guide.

Also, note that while we’re using the sftp command and the Linux file manager in this guide, many Linux administrators and users prefer using third-party FTP/SFTP clients such as FileZilla to send and receive files via SFTP, citing the ease of use of these FOSS clients.

Install OpenSSH

On many Linux distros, OpenSSH is installed by default.OpenSSH is the de facto standard open-source implementation of the SSH protocol used by most operating systems, including most Linux distros and Microsoft Windows.

To check if OpenSSH is installed on your Debian- or Ubuntu-based distro, enter the following from the terminal:

# dpkg -l grep ssh

On RHEL- and CentOS-based distros:

# rpm -qa openssh

On Arch-based distros:

# pacman -Qi openssh

On OpenSUSE-based distros:

# zypper search -i openssh

If no OpenSSH packages (openssh*) are listed, OpenSSH needs to be installed. OpenSSH can be installed with a single command-line entry.

To install OpenSSH on Debian- and Ubuntu-based distros:

# apt install openssh-server openssh-client

On RHEL- and CentOS-based distros:

# yum install openssh

On Arch-based distros:

# pacman -S openssh

On OpenSUSE-based distros:

# zypper install openssh-server

Configure OpenSSH

Now that the OpenSSH server, client, and SFTP server, along with dependent packages, are installed (these dependencies, libcor0.8, lifgido2-1, ssh-import-id, and openssh-sftp-server are automatically included when specifying openssh-server in the command line), we need to configure OpenSSH. Configuration of OpenSSH on a Linux distro consists of four separate steps:

• Create SFTP Group and User(s)
• Create SFTP Default Directory and Set Permissions
• Configure the SFTP Server Configuration File
• Restart OpenSSH

Note: The steps below need only be run on the distro serving as the SFTP server, not on client machines connecting to the SFTP server.

Create the SFTP Group and User(s)

In this example, the SFTP user id being created is sftp-user. The SFTP group is sftp-group.

1. Launch the terminal.
2. Create the SFTP group, sftp-group.

   # addgroup sftp-group

3. Create the SFTP user. sftp-user, and add them to the newly-created SFTP group, sftp-group.

   # sudo useradd -G sftp-group -d /sftp/sftp-user -s /sbin/nologin sftp-user

   Explanation of operators used:

   -G sftp-group:  add the user to the group sftp-group.
   -d /sftp/sftp-user:  specify the home directory of the user, sftp-user.
   -s /sbin/nolgin:  set the user, stfp-user, default shell to /sbin/nologin/. This means sftp-user will not be able to log in via SSH, only via SFTP.

4. Set the password for the user, sftp-user, with the passwd command.

   # passwd sftp-user

    

   

   Also, in this example, /sftp is the default root directory for SFTP users, and /sftp/<username> the home directory for each SFTP user (in this instance, sftp-user). When SFTP users login via SFTP, their default directory will be /sftp/<username>.

Create the SFTP Default Directory and Set Permissions

1. Create the /sftp/sftp-users/uploads directory.

   # mkdir -p /sftp/sftp-users/uploads

   Note that the -p option creates the parent directories if they don’t already exist. So the /sftp and /sftp/sftp-users/ directories are created along with /sftp/sftp-sftp-user/uploads.

2. Set the owner of the /sftp/sftp-users directory as root and give access to members of the group, sftp-group. Since /sftp is a root directory, root is the owner by default.

   # chown -R root.sftp-group /sftp/sftp-user

3. Set the owner of the /sftp/sftp-users directory as sftp-user and give access to members of the group, sftp-group.

   # chown -R sftp-user.sftp-group /sftp/sftp-user/uploads

4. Give read and execute permissions to members of the group, sftp-group.

   # chmod g+rx /sftp/sftp-user

5. Next, let’s verify that the /sftp subdirectory structure was created correctly and that ownership/permissions were correctly set.

   # ls -Ral /sftp

   

   With the permissions set above SFTP users (sftp-user) can read and copy from their SFTP home directory, /sftp/sftp-user, but cannot copy or write files to the directory. The only directory that the SFTP user can write files to is the uploads directory, /sftp/sftp-user/uploads.

Configure the SFTP Server Configuration File

Next, we need to configure the SFTP server configuration file, /etc/ssh/sshd_config.

1. To edit /etc/ssh/ssd_config, we must open it with a command-line text editor. In this case, that editor is Vim.

   # vi /etc/ssh/sshd_config

2. Add the following entries at the end of the file (under the Subsystem sftp /usr/lib/openssh/sftp-server) line.

   Match group sftp-group
   ChrootDirectory /sftp/%u
   X11Forwarding no
   AllowTcpForwarding no
   PermitTTY no
   ForceCommand internal-sftp

3. Save the /etc/ssh/sshd_config file.

   

Restart OpenSSH

Now that the necessary entries are in /etc/ssh/sshd_config, restart the OpenSSH server, (sshd daemon) for the changes to take effect.

# systemctl restart sshd

Note that even if the OpenSSH server is not running, the restart option will still start it.

Now, check that the OpenSSH server is running.

# systemctl status sshd

Real-Life Scenario – Send and Receive Files via SFTP using the GUI

In this scenario, the file, blue.txt, will be downloaded from the SFTP server to the client machine via drag-n-drop. Transferring files using SFTP via the GUI is much the same as copying files locally.

1. Launch the distro’s file manager (in this case, Nautilus).
2. Navigate to Other Locations.
3. Enter the SFTP server’s hostname or IP address in the Connect to Server box at the bottom of the file manager. In this instance, sftp://192.168.1.80. Note the sftp:// prefix. This is mandatory.
4. Click Connect.

   

5. When the authentication window appears, enter the user id, sftp-user, and password in the appropriate boxes. Click Connect.

   

6. When the SFTP server directory opens, the desired file, blue.txt, is in the directory.

   

7. Launch another file manager window and navigate where the file, blue.txt, is to be copied (Home / techobservatory downloads).

   

8. Select the file, blue.txt, in the SFTP server directory and drag-n-drop it into the desired directory.
9. The file, blue.txt, was successfully downloaded to the desired directory, Home / techobservatory downloads, on the client machine.

   

Real-Life Scenario – Send and Receive Files via SFTP using the Command Line

In this scenario, the file, pink.txt, will be sent from the client machine to the SFTP server via the command line.

1. Launch the terminal.
2. Enter sftp <sftp user>@<server>. In this case, sftp-user@192.168.1.80. Note that the hostname can be used as well as the IP address.

   # sftp sftp-user@192.168.1.80

3. At the SFTP prompt, change to the uploads directory.

   sftp> cd uploads

4. Send the file, pink.txt, to the SFTP server.

   sftp> put pink.txt

   The file’s transfer progress is displayed on the screen.

5. Verify that the file, pink.txt, is in the directory.

   sftp> dir

6. Exit SFTP.

   sftp> exit

   

7. Close the terminal.

In this scenario, the file, brown.txt, will be copied from the SFTP server to the client machine via the command line.

1. Launch the terminal.
2. Enter sftp <sftp user>@<server>. In this case, sftp-user@192.168.1.80. Note that the hostname can be used as well as the IP address).

   # sftp sftp-user@192.168.1.80

3. At the SFTP prompt, make sure the file to be copied, brown.txt, from the SFTP server to the client machine is present on the SFTP server.

   sftp> dir

4. Copy the file, brown.txt, to the client machine.

   sftp> get brown.txt

5. After the file, brown.txt is successfully retrieved, the SFTP prompt will reappear.
6. Exit SFTP.

   sftp> exit

   

7. Close the terminal.

Commands Used in This Article

Linux Commands Used

• ls – list directory contents.
• apt – Debian- and Ubuntu-based command-line interface for the package management system.
• rpm – (Remote Package Manager) package manager to install applications and packages on RHEL- and CentOS-based distros.
• pacman – package manager to install applications on Arch-based systems.
• useradd – add a user.
• addgroup – add a group.
• passwd – set or change a user’s password.
• dpkg – package manager for Debian- and Ubuntu-based distros.
• mkdir – make a directory.
• chown – change ownership of a file or directory.
• chmod – change file mode bits.
• sftp – launch the OpenSSH client.
• systemctl – control the systemd system and service manager.
• vi – launch the Vim text editor.

SFTP Commands Used

• dir – list directory contents.
• cd – change directory.
• exit – exit SFTP. bye and quit can also be used.
• put – copy a file to the SFTP server.
• get – retrieve a file from the SFTP server.

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