User and Group Management in Linux

How to list all users and groups on a Linux system

Let’s find out how to list all the users and groups on a Linux system. We will also cover how to find out which users are currently logged on to the system, and how to distinguish between system users and normal users.

Listing all users

There are a few different ways to list all the users on a Linux system. The most common way is to use the cat command to read the /etc/passwd file. This file contains information about all the users on the system, including their username, password (in encrypted form), user ID (UID), group ID (GID), and full name.

Here is an example of how to use the cat command to list all the users on a Linux system:

cat /etc/passwd

This will output a list of all the users on the system, along with their associated information.

Another way to list all the users on a Linux system is to use the getent command. The getent command can be used to retrieve information from a variety of databases, including the /etc/passwd file.

Here is an example of how to use the getent command to list all the users on a Linux system:

getent passwd

This will output a list of all the users on the system, along with their associated information.

Listing all groups

There are a few different ways to list all the groups on a Linux system. The most common way is to use the cat command to read the /etc/group file. This file contains information about all the groups on the system, including their group name, group ID (GID), and a list of users who belong to that group.

Here is an example of how to use the cat command to list all the groups on a Linux system:

cat /etc/group

This will output a list of all the groups on the system, along with their associated information.

Another way to list all the groups on a Linux system is to use the getent command. The getent command can be used to retrieve information from a variety of databases, including the /etc/group file.

Here is an example of how to use the getent command to list all the groups on a Linux system:

getent group

This will output a list of all the groups on the system, along with their associated information.

Finding out which users are currently logged on

There are a few different ways to find out which users are currently logged on to a Linux system. The most common way is to use the who command. The who command will output a list of all the users who are currently logged on to the system, along with their username, terminal name, and the time they logged on.

Here is an example of how to use the who command to find out which users are currently logged on to a Linux system:

who

This will output a list of all the users who are currently logged on to the system, along with their associated information.

Another way to find out which users are currently logged on to a Linux system is to use the w command. The w command will output a list of all the users who are currently logged on to the system, along with their username, terminal name, the time they logged on, and the last time they were active.

Here is an example of how to use the w command to find out which users are currently logged on to a Linux system:

w

This will output a list of all the users who are currently logged on to the system, along with their associated information.

Distinguishing between system users and normal users

System users are users who are created for system tasks, such as running daemons or managing files. Normal users are users who are created for human users to log in to the system.

There are a few ways to distinguish between system users and normal users. One way is to look at the user ID (UID) of the user. System users typically have a UID of 0 or less, while normal users typically have a UID of 100 or more.

Another way to distinguish between system users and normal users is to look at the group ID (GID) of the user. System users typically belong to the root group, while normal users typically belong to a different group, such as the users group.

Finally, you can also look at the full name of the user. System users typically have a full name that is descriptive of their purpose, such as root or daemon. Normal users typically have a full name that is the same as their username.

I hope this blog post has been helpful. If you have any questions, please feel free to leave a comment below.

Examples

Here are some examples of how to use the commands we have discussed in this blog post:

• To list all the users on a Linux system:

cat /etc/passwd

• To list all the groups on a Linux system:

cat /etc/group

• To find out which users are currently logged on to a Linux system:

who

• To distinguish between system users and normal users:

cat /etc/passwd | grep '^root:'

• To list all the users who belong to the users group:

cat /etc/passwd | grep '^users:'