Category Archives: Linux

How to Change user password in Linux

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.

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.

How to Move Files and Directories in Linux with mv Command

Mv is one of the Linux commands that must be learned. Mv stands for transferring files or directories from one place to another and is primarily used for moving them.

The syntax is similar to the cp command in Linux, but there is a fundamental distinction between these two commands.

The cp command can be called a copy-paste method. The mv instruction, while the cut-paste process can be equivalent.

This means the file or directory is transferred to a different location using the mv command on a file or directory. The source file/directory is no longer there.

mv Command How can you use it?

The mv(transfer) command will move files and directories from place to place. It is also ideal for renaming files and folders.

mv [OPTIONS] source destination
  • The source may be a single file or directory in the above command. The destination is always a single file or directory.
  • When we have several files or folders, it is always a directory destination. Both source files and folders, in this case, are transferred to the directory of the destination. When we have a single source file and a destination directory, the file is transferred to the target folder.
  • One crucial point is that when we transfer files and folders, we will obtain permission refused if we don’t have written permissions both for the source and destination.

mv mv image.png PNG

The current working directory transfers the image.png file to the PNG folder in the current work directory.

The original filename is renamed as the destination file if the destination directory isn’t present.

The image.png file is called PNG if it is not present in the existing working directory.

Transfer several folders and files

Specify the files you want to transfer as the source to move several files and folders. For instance, you would type to transfer file1 and file2 to the directory dir1:

mv File1 File2 dir1

You can also use pattern matching with the mv button. For, e.g., you would like to transfer all pdf files to the ~/Documents directory from the existing directory:

mv *.pdf ~/Documents

Drag a folder inside a separate folder with the mv command
We may use the following command to transfer a directory within another directory:

mv mv abcd abcd_New

It passes the abcd directory to another abcd New directory in our existing working directory.
The source directory is reset to the destination directory if the destination directory is not present.

How to transfer several files to another directory:
All source files and the path to the target directory are defined to transfer several files within a different directory.

mv <source(source)file path 3>

Our current working directory transfers the files 1.jpg, 2.jpg, and 2.png into a separate image directory in the current working directory.

Within a directory, we can transfer multiple files using regular expressions that match the filenames to be transferred.

Mv *jpg JPG

All files with mv backup:
We use the -b option to back up current files. It is intended to create a backup of the overwritten ~ character file with the attached backup file name.

mv -b a.jpg 1.jpg

ls

File rename

The mv command is essential for file renaming. The source file shall be renamed to the target file if you are using an mv command and specify a file name in your destination.
mv source_file target directory/target file

Suppose the target file does not exist in the target directory. In that case, the target file will be generated in the above case.

However, it overwrites without asking if the target file already exists. This means that with the source file’s content, the content of the current target file will be modified.

OverRight file when moving:

The existing file contents would be automatically overridden if a file is transferred and there is already a file with the same name.

In all cases, this might not be optimal. The overwriting scenario is available in a variety of ways.
You may use the -n option to avoid overwriting existing files. So mv will not overwrite the current file.

mv -n source_file target_directory

Forced movement of the file:

If you are shielded from writing the target file, you will be required to check until the target file is overwritten.

mv file1.txt target
Mv: substitute 'target/file1.txt' for 0444 overriding (r—r—r—) mode?

You may use the force option -f to bypass this prompt and overwrite the file immediately.

mv -f File1.txt target

Fdisk Command in Linux (Create Disk Partitions)

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.

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

Fdisk Command in Linux

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.

Chown Command in Linux (File Ownership)

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.

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.