Category: Linux

This tutorial focuses on setting up and configuring a SSH server on a Debian 10 minimal server

SSH, for Secure Shell, is a network protocol that is used in order to operate remote logins to distant machines within a local network or over Internet. SSH architectures typically includes a SSH server that is used by SSH clients to connect to the remote machine.

As a system administrator, it is very likely that you are using SSH on a daily basis to connect to remote machines across your network.

As a consequence, when new hosts are onboarded to your infrastructure, you may have to configure them to install and enable SSH on them.

In this tutorial, we are going to see how you can install and enable SSH, via OpenSSH, on a Debian 10 distributions.

Prerequisites

In order to install a SSH server on Debian 10, you will need to have sudo privileges on your host.

To check whether you have sudo privileges or not, run the following command

$ sudo -l

If you are seeing the following entries on your terminal, it means that you have elevated privileges

By default, the ssh utility should be installed on your host, even on minimal configurations.

In order to check the version of your SSH utility, you can run the following command

$ ssh -V

As you can see, I am running OpenSSH v7.9 with OpenSSL v1.1.1.

Note that it does not mean that SSH servers are installed on my host, it just means that I may able to connect to remote machines as a client using the SSH utility.

It also means that specific utilities related to the SSH protocol (such as scp for example) or related to FTP servers (such as sftp) will be available on my host.

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Installing OpenSSH Server on Debian 10

First of all, make sure that your packages are up to date by running an update command

$ sudo apt-get update

In order to install a SSH server on Debian 10, run the following command

$ sudo apt-get install openssh-server

The command should run a complete installation process and it should set up all the necessary files for your SSH server.

If the installation was successful, you should now have a sshd service installed on your host.

To check your newly installed service, run the following command

$ sudo systemctl status sshd

By default, your SSH server is going to run on port 22.

This is the default port assigned for SSH communications. You can check if this is the case on your host by running the following netstat command

$ netstat -tulpn | grep 22

Great! Your SSH server is now up and running on your Debian 10 host.

Enabling SSH traffic on your firewall settings

If you are using UFW as a default firewall on your Debian 10 system, it is likely that you need to allow SSH connections on your host.

To enable SSH connections on your host, run the following command

$ sudo ufw allow ssh

Enable SSH server on system boot

As you probably saw, your SSH server is now running as a service on your host.

It is also very likely that it is instructed to start at boot time.

To check whether your service is enable or not, you can run the following command

$ sudo systemctl list-unit-files | grep enabled | grep ssh

If no results are shown on your terminal, enable the service and run the command again

$ sudo systemctl enable ssh

Configuring your SSH server on Debian

Before giving access to users through SSH, it is important to have a set of secure settings to avoid being attacked, especially if your server is running as an online VPS.

As we already saw in the past, SSH attacks are pretty common but they can be avoided if we change default settings available.

By default, your SSH configuration files are located at /etc/ssh/

In this directory, you are going to find many different configuration files, but the most important ones are :

• ssh_config: defines SSH rules for clients. It means that it defines rules that are applied everytime you use SSH to connect to a remote host or to transfer files between hosts;
• sshd_config: defines SSH rules for your SSH server. It is used for example to define the reachable SSH port or to deny specific users from communicating with your server.

We are obviously going to modify the server-wide part of our SSH setup as we are interested in configuring and securing our OpenSSH server.

Changing SSH default port

The first step towards running a secure SSH server is to change the default assigned by the OpenSSH server.

Edit your sshd_config configuration file and look for the following line.

#Port 22

Make sure to change your port to one that is not reserved for other protocols. I will choose 2222 in this case.

When connecting to your host, if it not running on the default port, you are going to specify the SSH port yourself.

Please refer to the ‘Connecting to your SSH server’ section for further information.

Disabling Root Login on your SSH server

By default, root login is available on your SSH server.

It should obviously not be the case as it would be a complete disaster if hackers were to login as root on your server.

If by chance you disabled the root account in your Debian 10 installation, you can still configure your SSH server to refuse root login, in case you choose to re-enable your root login one day.

To disable root login on your SSH server, modify the following line

#PermitRootLogin

PermitRootLogin no

Configuring key-based SSH authentication

In SSH, there are two ways of connecting to your host : by using password authentication (what we are doing here), or having a set of SSH keys.

If you are curious about key-based SSH authentication on Debian 10, there is a tutorial available on the subject here.

Restarting your SSH server to apply changes

In order for the changes to be applied, restart your SSH service and make sure that it is correctly restarted

$ sudo systemctl restart sshd
$ sudo systemctl status sshd

Also, if you change the default port, make sure that the changes were correctly applied by running a simple netstat command

$ netstat -tulpn | grep 2222

Connecting to your SSH server

In order to connect to your SSH server, you are going to use the ssh command with the following syntax

$ ssh -p <port> <username>@<ip_address>

If you are connecting over a LAN network, make sure to get the local IP address of your machine with the following command

$ sudo ifconfig

For example, in order to connect to my own instance located at 127.0.0.1, I would run the following command

$ ssh -p 2222 <user>@127.0.0.1

You will be asked to provide your password and to certify that the authenticity of the server is correct.

Exiting your SSH server

In order to exit from your SSH server on Debian 10, you can hit Ctrl + D or type ‘logout’ and your connection will be terminated.

Disabling your SSH server

In order to disable your SSH server on Debian 10, run the following command

$ sudo systemctl stop sshd
$ sudo systemctl status sshd

From there, your SSH server won’t be accessible anymore.

Troubleshooting

In some cases, you may run into many error messages when trying to setup a SSH server on Debian 10.

Here is the list of the common errors you might get during the setup.

Debian : SSH connection refused

Usually, you are getting this error because your firewall is not properly configured on Debian.

To solve “SSH connection refused” you have to double check your UFW firewall settings.

By default, Debian uses UFW as a default firewall, so you might want to check your firewall rules and see if SSH is correctly allowed.

$ sudo ufw status

Status: active
 
To                         Action      From
--                         ------      ----
22/tcp                     ALLOW       Anywhere

If you are using iptables, you can also have a check at your current IP rules with the iptables command.

$ sudo iptables -L -n

Chain INPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:ssh

If the rule is not set for SSH, you can set by running the iptables command again.

$ sudo iptables -I INPUT -p tcp -m tcp --dport 22 -j ACCEPT

Debian : SSH access denied

Sometimes, you may be denied the access to your SSH server with this error message “SSH access denied” on Debian.

To solve this issue, it depends on the authentication method you are using.

SSH password access denied

If you are using the password method, double check your password and make sure you are entering it correctly.

Also, it is possible to configure SSH servers to allow only a specific subset of users : if this is the case, make sure you belong to that list.

Finally, if you want to log-in as root, make sure that you modified the “PermitRootLogin” option in your “sshd_config” file.

#PermitRootLogin

PermitRootLogin yes

SSH key access denied

If you are using SSH keys for your SSH authentication, you may need to double check that the key is correctly located in the “authorized_keys” file.

If you are not sure about how to do it, follow our guide about SSH key authentication on Debian 10.

Debian : Unable to locate package openssh-server

For this one, you have to make sure that you have set correctly your APT repositories.

Add the following entry to your sources.list file and update your packages.

$ sudo nano /etc/apt/sources.list

deb http://ftp.us.debian.org/debian wheezy main

$ sudo apt-get update

Conclusion

In this tutorial, you learnt how you can install and configure a SSH server on Debian 10 hosts.

You also learnt about basic configuration options that need to be applied in order to run a secure and robust SSH server over a LAN or over Internet.

If you are curious about Linux system administration, we have a ton of tutorials on the subject in a dedicated category.

Adding and deleting users is one of the most basic tasks when starting from a fresh Debian 10 server.

Adding user can be quite useful. As your host grows, you want to add new users, assign them special permissions, like sudo rights for example.

In this tutorial, we are going all the ways to add and delete users on Debian 10 hosts.

Prerequisites

In order to add and delete users on Debian, you need to have sudo rights, or to belong to the sudo group.

If you are not sure about how to add a user to sudoers, make sure to check the tutorial we wrote about it.

To check your sudo rights, run the following command

$ sudo -v

If no error messages appear, you are good to go, otherwise ask your system administrator to provide you with sudo rights.

Adding a user using adduser

The first way to add users on Debian 10 is to use the adduser command.

The adduser command is very similar to the useradd command. However, it provides a more interactive way to add users on a Debian host.

Generally, it is preferred to use adduser rather than useradd (as recommended by the useradd man page itself)

To add a user, run this command

$ sudo adduser ricky

Adding user 'ricky'
Adding new group 'ricky' (1007)
Adding new user 'ricky' (1005) with group 'ricky'
Creating home directory '/home/ricky'
Copying files from '/etc/skel'

You will be asked to choose a password for the user

New password: <type your password>
Retype new password: <retype your password>
Changing the user information for ricky

Then you will be asked to specify some specific information about your new user.

You can leave some values blank if you want by pressing Enter.

Enter the new value, or press ENTER for the default
   Full Name []:
   Room Number []:
   Work Phone []:
   Home Phone []:
   Other []:

Finally, you will be asked if the information provided is correct. Simply press “Y” to add your new user.

Is the information correct? [Y/n] Y

Now that your user was created, you can add it to the sudo group.

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Adding a user using useradd

$ sudo useradd <username>

To assign a password to the user, you can use the -p flag but it is not recommended as other users will be able to see the password.

To assign a password to a user, use the passwd command.

$ sudo passwd <username>

New password:
Retype new password:
passwd: password updated successfully

Add a user using the GNOME desktop

If you installed Debian 10 with GNOME, you can also create a user directly from the desktop environment.

In the Applications search bar, search for “Settings”.
In the Settings window, find the “Details” option.

Click on “Details”, then click on “Users”.

On the top right corner of the window, click on “Unlock”.

Enter your password, and a “Add User” option should now appear in the panel.

In the next window, choose what type of account you want for the user (either with sudo rights or not).

Fill the full name field, as well as the username field.

You can choose to assign a password now or you can let the user decide on its password on its next logon.

When you are done, simply click on “Add”.

Congratulations, your account was successfully created.

Check that your user was added

In order to check that your user was created on Linux, run the following command.

$ cat /etc/passwd | grep <user>
<user>:x:1005:1007:User,,,:/home/user:/bin/bash

If there are no entries for the user you just created, make sure to use the adduser command again.

Deleting a user using deluser

In order to delete a user on Debian 10, you have to use the deluser command.

$ sudo deluser <username>

To remove a user with its home directory, run the deluser command with the –remove-home parameter.

$ sudo deluser --remove-home <username>

Looking for files to backup/remove
Removing user 'user'
Warning: group 'user' has no more members.
Done.

To delete all the files associated with a user, use the –remove-all-files parameter.

$ sudo deluser --remove-all-files <username>

Deleting a sudo user with visudo

If you removed a sudo user on Debian, it is very likely that there is a remaining entry in your sudoers file.

To delete a user from the sudoers file, run visudo.

$ sudo visudo

Find the line corresponding to the user you just deleted, and remove this line.

<username>    ALL=(ALL:ALL) ALL

Save your file, and your user should not belong to the sudo group anymore.

Deleting a user using the GNOME Desktop

From the users panel we used to create a user before, find the “Remove user” option at the bottom of the window.

Note : you need to unlock the panel to perform this operation.

When clicking on “Remove User”, you are asked if you want to keep the files owned by this user. In this case, I will choose to remove the files.

Troubleshooting

In some cases, you may have some error messages when trying to execute some of the commands above.

adduser : command not found on Debian

By default, the “adduser” command is located in the “/usr/sbin” folder of your system.

$ ls -l /usr/sbin/ | grep adduser
-rwxr-xr-x 1 root root    37322 Dec  5  2017 adduser

To solve this issue, you need to add “/usr/sbin” to your $PATH.

Edit your .bashrc file and add the following line

$ sudo nano ~/.bashrc

export PATH="$PATH:/usr/sbin/"

Source your bashrc file and try to run the adduser command again.

$ source ~/.bashrc

$ sudo adduser john
Adding user `john' ...
Adding new group `john' (1001) ...
Adding new user `john' (1001) with group `john' ...
Creating home directory `/home/john' ...
Copying files from `/etc/skel' ...

You solved the “adduser : command not found” problem on Debian 10.

Conclusion

As you can see, adding and deleting users on Debian 10 is pretty straightforward.

Now that your users are created, you can also set up SSH keys on Debian 10 for a seamless authentication.

Every system administrator got this error at least one time in a shell : “bash : command not found“.

However, you were pretty sure that you wrote the command correctly, or that you installed the tool that you are actually trying to execute.

So why are you getting this error?

The “bash : command not found” error can happen for various reasons when running commands in a Bash terminal.

Today, we are taking a look at the different ways to solve the “command not found” error in Bash.

Bash & PATH concepts

Before starting out with the solution, it is important to have a few concepts about what the PATH environment variable is and how it is related to the commands you run.

PATH is an environment variable that lists the different directories that your bash terminal will visit in order to find utilities on your system.

To have a look at your PATH environment variable, simply use the “echo” command with the PATH variable.

$ echo $PATH

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

As you can see, PATH is defined by a list of different system paths delimited by colons.

They are the different paths visited by my interpreter in order to run commands.

If I were to remove an entry from the PATH, or remove the PATH all together, you would not be able to run commands in the bash without specifying the entire path to the binary.

It is an important point to understand because not being able to run a command does not mean that your binary was deleted on the system.

Now that you understand how environment variables are related to your bash interpreter, let’s see how you can solve your error.

Verify that the file exists on the system

The first step to solve this error is to verify that the command you are looking for actually exist on the system.

There are really no points going further if you mispelled the command or if you didn’t install it at all.

Let’s say for example that you cannot run the “ls” command.

Verify that the binary actually exists by searching for the binary on the system.

$ /usr/bin/find / -name ls 2> /dev/null

/bin/ls
/usr/lib/klibc/bin/ls

With the find command, you are able to locate the binary along with the directory where it is stored.

It is quite important because we will need to add this path to our PATH environment variable later on.

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Verify your PATH environment variable

Most of the time, you will run into the “bash : command not found” after changing your PATH environment in order to add new entries.

First, verify that the path you searched for before is listed in your PATH environment variable.

$ echo $PATH

/home/user/custom:/home/user

As you can see here, the “/bin” directory is not listed in my PATH environment variable.

By default, the PATH is defined in the “/etc/environment” file for all the users on the system.

If your PATH environment variable is different from the one defined in the environment file, it is because you have overriden the PATH.

Now that you have two choices : either you know where you exported the PATH variable or you don’t.

Fixing your profile scripts : bashrc, bash_profile

In most of the cases, you modified the .bashrc or the .bash_profile file in order to add your PATH override.

To search where you exported your PATH, run the following command

$ /usr/bin/grep -rn --color "export PATH" ~/. 2> /dev/null

./.bashrc:121:export PATH="/home/devconnected"

This command returns the file where the PATH was exported as well as the line number.

Edit this file and add the path from the first section to the export statement.

$ nano /home/user/.bashrc

export PATH="/home/devconnected:/bin"

Save your file and exit the nano editor.

For the changes to be applied, you will have to source your current bash terminal.

This will ensure that the .bashrc file is executed again in the current shell terminal.

$ source .bashrc

Why can you execute source without having to specify the full path?

Because “source” is a shell built-in command.

Try executing “builtin source .bashrc” for example

Now, you can try to execute the command you failed to execute before.

$ ls

file  devconnected  file2  directory1  swap file3

Awesome!

You fixed the “bash : command not found” error on Linux!

Reset the PATH environment variable properly

Even if you solve your issue, you will have to define your PATH environment variable properly if you don’t want to modify your bashrc file all the time.

First, have a look at the PATH variable defined in the “/etc/environment” file.

$ cat /etc/environment

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"

In order to reset your PATH environment variable on your environment, export the PATH defined in the environment file.

$ export=PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"

Now, modify your .bashrc file but use the $PATH syntax in order to append your paths to the existing PATH variable.

$ sudo nano ~/.bashrc

export PATH="$PATH:/home/devconnected"

Exit the file and source your bashrc file for the changes to be applied.

$ source ~/.bashrc

$ echo $PATH

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/home/devconnected

Awesome!

You have successfully resetted your PATH environment variable, you should not get the “bash : command not found” error anymore.

Execute the command as sudo

In some cases, your PATH environment variable may be perfectly configured but you will have to execute the command as sudo.

You may get this error or just a simple “permission denied” error.

In any cases, first make sure that you have sudo rights with the sudo command.

$ sudo -l

User user may run the following commands on ubuntu:
    (ALL : ALL) ALL

If this is the case, you should be able to execute your command as sudo.

$ sudo <command>

Congratulations!

You have solved the “bash : command not found” error on your system.

Verify that the package is correctly installed

In some cases, you think that your command is installed but you didn’t install the command to begin with.

Let’s say for example that you are looking to run the “htop” command but you are not able to do it.

$ htop

bash : Command 'htop' not found

To verify if the command is correctly installed, depending on your distribution, run the following commands.

$ dkpg -s htop     [Ubuntu/Debian]

dpkg-query: package 'htop' is not installed and no information is available
Use dpkg --info (= dpkg-deb --info) to examine archive files,
and dpkg --contents (= dpkg-deb --contents) to list their contents.

$ rpm -qa | grep htop    [CentOS/RHEL]

In any case, you will have to install the command if you want to run it properly.

$ sudo apt-get install htop   [Ubuntu/Debian]

$ sudo yum install htop       [CentOS/RHEL]

Now you can try to run the command that was missing.

$ htop

Conclusion

In this tutorial, you learnt how you can solve the famous “bash : command not found” error that many system administrators encounter every day.

If you solve your issue with a solution that is not described in the article, make sure to leave a comment in order to help other administrators.

If you are interested in Linux system administration, we have a complete section dedicated to it on the website, so make sure to have a look.

This write-up is being provided to guide you through the procedure of changing your own user password in the application named Linux.

One interesting thing is that you can even forcefully make users change the password used for a login in Linux and that will be discussed here.

The procedural steps that are being provided here in this guide can also be used in other applications like Ubuntu, Debian, and CentOS.

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Putting in the required changes in your already existing Password

If you wish to change the login details specifically the user password for your user login you will have to provide the command mentioned below with no other tit- bits following,

 $ passwd

Changing password for linuxize.

(Current) UNIX password:

Enter new UNIX password:

Retype new UNIX password:

passwd: password updated successfully

Once you put in the command $ password, a screen with the text mentioned above will pop up asking you the below-mentioned questions,

• What is your current password?
• What is the new password? Entering new password
• Mention the new password again

Following the procedure above you will be easily able to bring the required changes in your user password.

Always remember that while filling the answers to the above questions you will not find them being showcased on the screen and front and that is totally normal.

Finally, when you try logging in to your system you will find that your new password has been generated and you can login using the freshly brewed user password.

How to facilitate change in password of another user?

It is not a factor to be surprised with as it has been already acquainted with you that access is granted to only the user who is rooted to the account or a user who has a sudo connection to the account will be provided the required privilege for making changes in the refreshed password for the account. The process that will be mentioned below is being mentioned keeping in mind that you are someone with the privilege of being connected to the account being handled as a sudo user.

When you are designing a change in a password for a different account you will have to type in the password command and entailing it should be the username of the account needing password changes. If we consider a password change in the account named lineux then the command followed will be,

$ sudo password lineux

Next step will be you coaxed into filling in a new password and confirming it:

Output

Enter new UNIX password:

Retype new UNIX password:

Once you are at the end of the procedure you will be faced with a command exactly like below,

Output

$ Password: password updated successfully

How can a user be pressured to change password at next login?

It has been set by default in many applications that the password set by a user for login details does not ever expire. Now a user can be pressurized to change the password when logging in for another time by undergoing a few commands while on the portal for Linux. The command that is provided for expiration of the old password is entailed by the name of the user:

$ sudo password --expire linuxize

Once you squeeze in the command mentioned above you will find the already existing password turning out to be immediately expired.

This procedure of immediate expiration of user’s earlier or old password will put pressure on the user to finally have the user password changed because of a message that will pop up when they log in again:

$ ssh linuxize@192.168.121.209

OUTPUT

WARNING: Your password has expired.

You must change your password now and login again!

Changing password for linuxize.

(Current) UNIX password:

Enter new UNIX password:

Retype new UNIX password:

password: password updated successfully

Connection to 192.168.121.209 closed.

You will see the connection being closed once the newly made and refreshed password is set by the user.

Conclusion

The write-up that was provided above was to help people with being able to bring out the required changes in their user password in a specific application named Linux.

The guidance that you got in the above right upper was how can you bring out the specific changes in the password and how can someone set an expiry limit to their password.

Whenever you install a new SSD or hard disk, the first thing you have to do is to partition it. A drive requires to have at least one partition before you can format it and store files on it.

In Linux, there are many tools that you can use to generate partitions, with fdisk being the most usually used one.

In this article, let us see about the fdisk command.

fdisk is a menu-driven command-line utility that enables you to design and manipulate partition tables on a hard disk.

Be aware that fdisk is a severe tool and should be used with absolute caution. Only root or users with sudo privileges can manage the partition tables.

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List Partitions

To list the partition table of a project, invoke the fdisk command with the -l option, followed by the device name. For example, to list the /dev/sda partition table and partitions, you would run:

$ fdisk -l /dev/sda

When no device is given as an argument, fdisk will print partition tables of all devices listed in the /proc/partitions file:

$ fdisk -l

Output:

Disk /dev/nvme0n1: 232.91 GiB, 250059350016 bytes, 488397168 sectors

Disk model: Samsung SSD 960 EVO 250GB

Units: sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disklabel type: gpt

Disk identifier: 6907D1B3-B3AB-7E43-AD20-0707A656A1B5

Device            Start       End   Sectors   Size Type

/dev/nvme0n1p1     2048   1050623   1048576   512M EFI System

/dev/nvme0n1p2  1050624  34605055  33554432    16G Linux swap

/dev/nvme0n1p3 34605056 488397134 453792079 216.4G Linux filesystem

Disk /dev/sda: 465.78 GiB, 500107862016 bytes, 976773168 sectors

Disk model: WDC WD5000AAKS-0

Units: sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disklabel type: dos

Disk identifier: 0x0001cca3

Device     Boot Start       End   Sectors   Size Id Type

/dev/sda1        2048 976771071 976769024 465.8G 83 Linux

The output over shows the current partition tables of all devices that are connected to your system. Generally, SATA device signs follow the pattern /dev/sd[a-z], while NVMe device signs have the following pattern /dev/nvme[1-9]n[1-9].

Creating Partition Table

To start partitioning the drive, run fdisk with the device name. In this example, we will work on /dev/sdb:

fdisk /dev/sdb

The command prompt will vary, and the fdisk dialogue where you can type in commands will open:

Welcome to fdisk (util-linux 2.34).

Corrections will remain in memory only until you decide to write them.

Be careful before using the write command.

Command (m for help):

Corrections you make to the partition table won't affect you until you write them with the w command. You can exit the fdisk dialogue without saving the changes using the q command.

To get a list of all available commands, enter m

(command m for help) m

If you are partitioning a new drive, you need to create a partition table before starting to create partitions. Skip this step if the device already has a partition table and you want to keep it.

fdisk supports several partitioning schemes. MBR and GPT are the two most popular partition scheme standards that store the partitioning information on a drive differently. GPT is a newer standard allowing and has many advantages over MBR. The main points to consider when choosing what partitioning standard to use:

• Use MBR to boot the disk in legacy BIOS mode.
• Use GPT to boot the disk in UEFI mode.
• The MBR standard supports creating a disk partition up to 2 TiB. If you have a disk of 2 TiB or larger, use GPT.
• MBR has a limit of 4 primary partitions. If you need more sections, one of the preceding sections can be set as an extended partition and hold additional logical partitions. With GPT, you can have up to 128 sections. GPT doesn’t support extended or logical partitions.

In this example, we will use a GPT partition table.

Enter g to create a new empty GPT partition table:

command (m for help) g

Output:

Created a new GPT disklabel (GUID: 4649EE36-3013-214E-961C-51A9187A7503).

The next step is to create the new partitions.

We will create two partitions. The first one with a size of 100 GiB, and the second one will take the rest of the disk space.

Run the n command to create a new partition:

command (m for help) n

You’ll be prompted to enter the partition number. Hit “Enter” to use the default value (1):

Partition number (1-128, default 1):

Next, the command will ask you to specify the first sector. Generally, it is always recommended to use the default values for the first value. Hit “Enter” to use the default value (2048):

First sector (2048-500118158, default 2048):

On the next prompt, you’ll need to enter the last sector. You can use an absolute value for the previous sector or relative importance to the start sector, using the + symbol following the partition size. The size can be specified in kibibytes (K), mebibytes (M), gibibytes (G), tebibytes (T), or pebibytes (P).

Enter +100G to set the partition size to 100 GiB:

Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-500118158, default 500118158): +100G

Output:

Created a new partition 1 of type' Linux filesystem' and size 100 GiB.

By default, the new partition type is set to “Linux filesystem,” which should be sufficient for most cases if you want to change the type, press l to get a list of partition types and then press t to change the style.

Let’s create the second partition that will take the rest of the disk space:

command (m for help) n

Partition number (2-128, default 2):

First sector (209717248-625142414, default 209717248):

Last sector, +/-sectors or +/-size{K,M,G,T,P} (209717248-625142414, default 625142414):

Once done creating partitions, use the p command to display the new partition table:

command (m for help) p

Disk /dev/sdb: 298.9 GiB, 320072933376 bytes, 625142448 sectors

Disk model: nal USB 3.0

Units: sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 4096 bytes

I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disklabel type: gpt

Disk identifier: F8365250-AF58-F74E-B592-D56E3A5DEED1

Device Start End Sectors Size Type

/dev/sdb1 2048 209717247 209715200 100G Linux filesystem

/dev/sdb2 209717248 625142414 415425167 198.1G Linux filesystem

If you want to delete a partition, use the d command.

Save the changes by running the w command:

command (m for help) p

The command will write the table to disk and exit the fdisk menu.

Output:

The partition table has been altered.

Calling ioctl() to re-read partition table.

Syncing disks.

The kernel will read the device partition table without the need to reboot the system.

Activating the Partitions

Now that the partitions have been created, the next step is to format the partitions and mount them to the system’s directory tree.

We’ll format both partitions to ext4:

sudo mkfs.ext4 -F /dev/sdb1sudo mkfs.ext4 -F /dev/sdb2

mke2fs 1.45.5 (07-Jan-2020)

Creating filesystem with 51928145 4k blocks and 12984320 inodes

Filesystem UUID: 63a3457e-c3a1-43f4-a0e6-01a7dbe7dfed

Superblock backups stored on blocks:

32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,

4096000, 7962624, 11239424, 20480000, 23887872

Allocating group tables: done

Writing inode tables: done

Creating journal (262144 blocks): done

Writing superblocks and filesystem accounting information: done

We will mount the partitions to /mnt/audio and /mnt/video directories in this example.

Create the mount points with mkdir :

sudo mkdir -p /mnt/audio /mnt/video

Mount the new partition:

sudo mount /dev/sdb1 /mnt/audio
sudo mount /dev/sdb2 /mnt/video

Partitions will stay mounted until you unmount it or shut down the machine. To automatically mount a partition when your Linux system starts up, define the mount in the /etc/fstab file.

That’s it! You can now use the new partitions to store your files.
Conclusion
fdisk is a command-line tool for creating partition schemes. For more information about the fdisk command, type man fdisk in your terminal.

If you want to change the user and/or group ownership of a given file, directory, or symbolic link, the chown command is used. So in this article, we will show you how to use the chown command through practical examples.

Let us see How to Use chown.

Before moving into how to use the chown command, let’s begin by examining the basic syntax.

• How To Chown Recursively on Linux
• Access Control Lists on Linux Explained | Linux ACL Cheat Sheet
• How To Encrypt Partition on Linux

The chown command expressions take the subsequent form:

chown [OPTIONS] USER[:GROUP] FILE(s)

USER is nothing but the user name or the user ID (UID) of the new owner. The name of the group ID (GID) or the new group is GROUP. The name of one or more directories, files, or links is FILE(s). Remember, always numeric IDs should be prefixed with the + symbol.

• USER – If only the user is defined, the defined user will grow the given file owner, the group ownership is not changed.
• USER: – When the username is succeeded by a colon: and the group name is not given, the user will become the owner of the files, and the files group ownership is transferred to the user’s login group.
• USER: GROUP – If both the group and the user are defined (with no space between them), the user ownership of the files is transferred to the given user, and the group ownership is transferred to the given group.
• GROUP – If the User is canceled and the group is prefixed with a colon, only the files’ group ownership is transferred to the given group.
• : If only a colon: is given, without defining the user and the group, no change is made in it.

By default, on success, chown doesn’t give any output and returns zero.

To find out who holds a file or what group the file refers to, use the ls -l command:

$ ls -l filename.txt

Output:

-rw-r--r-- 12 linuxize users 12.0K Apr 8 20:51 filename.txt

Regular users can replace the filegroup only if they own the file and only to a group they are a member of. Administrative users can replace the group ownership of all files.

How to Replace the Owner of a File

If you want to replace the owner of a file, then use the chown command succeeded by the user name of the new owner and the target file as an argument:

chown USER FILE

For example, the subsequent command will transfer the ownership of a file named file1 to a new owner named linuxize:

$ chown linuxize file1

To transfer the ownership of multiple files or directories, define them as a space-separated list. The command below turns the ownership of a file named file1 and directory dir1 to a new owner named linuxize:

$ chown linuxize file1 dir1

For example, the subsequent command will transfer the ownership of a file named file1 to a new owner named linuxize:

$ chown linuxize file1

To transfer the ownership of multiple files or directories, specify them as a space-separated list. The command following transfers the ownership of a directory with name dir1 and a file with name file1 to a new owner named linuxize:

$ chown linuxize file1 dir1

The alternatively used for the username is the numeric user ID (UID). The following example will transfer the ownership of a file named file2 to a new owner with a UID of 1000:

$ chown 1000 file2

If a numeric owner survives as a user name, then the ownership will be transferred to the user name. To bypass this, prefix the ID with +:

$ chown 1000 file2

How to Replace the Owner and Group of a File

If you want to replace both the owner and the group of a file, use the chown command supported by the new owner and group separated by a colon (:) with no intermediary spaces and the target file.

$ chown USER: GROUP FILE

The subsequent command will transfer the ownership of a file named file1 to a new owner named linuxize and group users:

$ chown linuxize: users file1

If you cancel the group name after the colon (:) the group of the file is replaced to the specified user’s login group:chown linuxize: file1

How to Replace the Group of a File

To replace only the group of a file, use the chown command followed by a colon (:) and the new group name (with no space between them) and the target file as an argument:

$ chown: GROUP FILE

The subsequent command will replace the owning group of a file named file1 to www-data:

$ chown :www-data file1

Another command that you can use to replace the group ownership of files is chgrp.

How to Replace Symbolic Links Ownership

When the recursive alternative is not used, the chown command replaces the group ownership of the files to which the symlinks point, not the symbolic links themselves.

For example, if you try to replace the owner and the group of the symbolic link symlink1 that points to /var/www/file1, chown will change the ownership of the file or directory the symlink points to:

$ chown www-data: symlink1

The possibilities are that instead of changing the target ownership, you will get an error “cannot dereference ‘symlink1’: Permission denied”.

The error happens because, by default on most Linux distributions, symlinks are protected, and you cannot work on target files. This option is defined in /proc/sys/fs/protected_symlinks. One means enabled, and zero means disabled. We suggest not to disable the symlink protection.

To replace the group ownership of the symlink itself, use the -h option:

$ chown -h www-data symlink1

How to Recursively Replace the File Ownership

To recursively run on all files and directories under the given directory, use the -R (–recursive) alternative:

$ chown -R USER: GROUP DIRECTORY

The following example will transfer the ownership of all files and subdirectories under the /var/www directory to a new owner and group named www-data:

$ chown -R www-data: /var/www

If the directory contains symbolic links, pass the -h option:

$ chown -hR www-data: /var/www

Other alternatives that can be used when recursively replacing the directory ownership are -H and -L.

If the argument passed to the chown command is a symbolic link pointing to a directory, the -H option will create the command to cross it. -L tells chown to cross each symbolic link to a guide that is found. Usually, it would be best to use these choices because you might mess up your system or perform a security risk.

Using a Reference File

The -- reference = ref_file option enables you to change the user and group ownership of given files to be the same as those of the detailed reference file (ref_file). Chown will use the target file user and group; if the reference file is a symbolic link.

$ chown --reference=REF_FILE FILE

For instance, the subsequent command will allow the user and group ownership of the file1 to file2

$ chown --reference=file1 file2

Conclusion

The chown is a Linux/UNIX command-line service for developing the file’s user and/or group ownership.

To discover more about the chown command, visit the chown man page or type man chown in your terminal. If you have any questions or feedback, please leave a comment below or contact us directly.

Renaming documents is one of the most common tasks you regularly want to carry out on a Linux system. You can rename documents by use of a GUI document manager or through the command-line terminal.

Renaming a single document is not hard however renaming more than one document at once may be a challenge, especially for customers who’re new to Linux.

In this tutorial, we will display you the way to use the mv and rename instructions to rename documents and directories.

• How to Rename Directories in Linux
• How To Rename a Directory on Linux
• How to Move Files and Directories in Linux with mv Command

Renaming Files with the mv Command

The mv command (short of circulate) is used to rename or circulate documents from one region to another.

Syntax used for the mv command is as follows:

mv [OPTIONS] source destination

Copy

The source may be one or more documents, or directories and destination may be a single document or directory.

If you specify more than one document as source, the destination should be a directory. In such cases, the source documents are transferred to the targeted directory.

If you specify a single document as source, and the destination target is a current directory, then the document is moved to the required directory.

To rename a document, you want to specify a single document as a source and a single document as a destination target.

For instance, to rename the document file1.txt as file2.txt you’ll run:

mv file1.txt file2.txt

Renaming more than one documents with the mv Command

The mv command can rename only one command at a time effectively  , however it may be used together with different commands which include find or inside bash for or while loops to rename more than one document.

The following instance indicates the way to use the Bash for loop to rename all .html documents in the present directory by converting the .html extension to .php.

for f in *.html; do

    mv -- "$f" "$f%.html">.php"

done

Copy

Let’s examine the code line by line:

The first line creates a for loop and iterates through a listing of all documents edging with .html.

The 2d line applies to every object of the listing and moves the document to a new one replacing .html with .php.

The element ${document%.html} is by use of the shell parameter expansion to get rid of the .html element from the filename.

done suggests the end of the loop segment.

Here is an example by use of mv in combination with find to gain similar above:

find . -depth -name "*.html" -exec sh -c 'f=""; mv -- "$f" "$.php"' ;

" xss="removed">Copy

The find command is passing all documents ending with .html in the present directory to mv one at a time using the -exec option. The string is the name of the document presently being processed.

As you could see from the examples above, renaming more than one document using the mv command isn’t an easy project because it requires a great amount of Bash scripting.

Renaming Files with the rename Command

The rename command is used to rename more than one document. This command is extra advanced than mv because it requires a few fundamental understanding of regular expressions. There are  variations of the rename command with unique syntax.

Here in this tutorial, we are going to use  the Perl version of the rename command. If you don’t have this version set up on your system, you could effortlessly install it by using the package manager of your distribution.

Install rename on Ubuntu and Debian

sudo apt install rename

Install rename on CentOS and Fedora

sudo yum install prename

Install rename on Arch Linux

yay perl-rename ## or yaourt -S perl-rename

The syntax for the rename command is as follows:

rename [OPTIONS] perlexpr documents

Copy

The rename command will rename the documents in step with the required perlexpr regular expression. You can study more about perl regular expressions here .

The following instance will change all documents with the extension .html to .php:

rename 's/.html/.php/' *.html

You can use the -n choice to print names of documents to be renamed, without renaming them.

rename -n 's/.html/.php/' *.html

The output will look something like this:

rename(file-90.html, file-90.php)

rename(file-91.html, file-91.php)

rename(file-92.html, file-92.php)

rename(file-93.html, file-93.php)

rename(file-94.html, file-94.php)

By default, the rename command doesn’t overwrite present documents. Pass the -f choice to permit present documents to be overwritten:

rename -f 's/.html/.php/' *.html

Below are some more common examples of how to use the rename command:

Replace areas in filenames with underscores

rename 'y/ /_/' *

Convert filenames to lowercase

rename 'y/A-Z/a-z/' *

Convert filenames to uppercase

rename 'y/a-z/A-Z/' *

Conclusion

Here we have shown you the way to use the mv and rename instructions to rename documents.

There also are different instructions to rename documents in Linux, which include mmv. New Linux customers who’re intimidated by the command line can use GUI batch rename equipment which include the Métamorphose .

If you’ve got any questions or feedback, Just feel free to leave a comment.

Renaming directories is one of the most primary operations you frequently want to perform on a Linux system. You can rename directories from the GUI document manager with more than one click or the use of the command-line terminal.

This article explains a way to rename directories by the use of the command-line.

Renaming Directories

In Linux and Unix-like running systems, you may use the mv (short of move) command to rename or circulate documents and directories from one place to any other.

The syntax of the mv command for shifting directories is as follows:

mv [OPTIONS] source destination

For instance, to rename the listing dir1as dir2 you will run:

mv dir1 dir2

When renaming directories, you need to specify precisely arguments to the mv command. The first argument is the present name of the directory, and the second argument is the new name.

It is essential to notice that if dir2 already exists, dir1 is moved to the dir2 directory.

To rename a listing that isn’t in the present  running directory, you want to specify both absolutely the or relative path:

mv /home/user/dir1 /home/user/dir2

• How to Rename Files and Directories in Linux
• How To Rename a Directory on Linux
• How to Move Files and Directories in Linux with mv Command

Renaming Multiple Directories

It is easy  to rename a single directory challenge, however renaming more than one directories straight away may be a challenge, specifically for new Linux users.

Renaming more than one directories straight away is not often needed.

Renaming Multiple Directories with mv

The mv command can rename the handiest one report at a time. However, it may be used along with different instructions such as find or interior loops to rename more than one document straight away.

Here is an example displaying a way to use the Bash for loop to append the present date to the names of all directories in the present operating directory:

for d in *; do

  if [ -d "$d" ]; then

    mv -- "$d" "$d">_$(date +%Y%m%d)"

  fi

done

Let’s examine the code line through line:

• The first line creates a loop and iterates by a listing of all documents.
• The 2nd line examines if the document is a directory.
• The 3rd line appends the present date to every directory.

Here is an answer to the same challenge the usage of mv in aggregate with find:

find . -mindepth 1 -prune -type d -exec sh -c 'd=""; mv -- "$d" "$_$(date +%Y%m%d)"' ;

The find command is passing all directories to mv one after the other the use of the -exec alternative. The string  is the name of the listing presently being processed.

As you may see from the examples, renaming more than one directories with mv isn’t an easy challenge because it requires a very good understanding of Bash scripting.

Renaming more than one directories with rename

The rename command is used to rename more than one document and directories. This command is superior to mv because it calls for a fundamental understanding of regular expressions.

There are  variations of the rename command with unique syntax. We use the Perl version of the rename command. The documents are renamed in step with the given perl ordinary expression .

The following instance suggests a way to update areas in the names of all directories in the present  operating listing with underscores:

find . -mindepth 1 -prune -type d | rename 'y/ /_/'

To be on the safe side, pass the -n alternative to rename to print names of the directories to be renamed without renaming them.

Here is any other instance displaying a way to convert listing names to lowercase:

find . -mindepth 1 -prune -type d | rename 'y/A-Z/a-z/'

Conclusion

We’ve proven you a way to use the mv instructions to rename directories.

If you’ve got  any questions or feedback, just  leave a comment.