This guide will help you understand what the passwd file is and the important role it plays when it comes to user management in Linux.
What Is /etc/passwd?
The passwd file in Linux is a configuration file that contains user details. An important characteristic of the passwd file is that it is an ASCII text file that users can edit easily using any text editor such as nano and vim.
Although you can add and manage users directly using the passwd file, it is not advisable because this action is prone to typos and errors. You should instead use the various user management commands such as useradd for adding users to your system.
Viewing the /etc/passwd File
To view the content of the passwd file, you can use any text editor or a file viewing command tool. In this guide, we will be using cat.
The output should be similar to the one below.
Each line actually represents one user on your system, so do not be surprised that you have so many users listed. Most of them are system users that control specific applications on your Linux machine. For example, the user mail is responsible for the Mail application.
The /etc/passwd Fields Explained
From the output above, it is very clear that the /etc/passwd file follows a very specific pattern.
Each user line is further subdivided into seven sections or fields separated by the colon character (:) as below.
1. Username
The first field in a line represents the username or login name of the user. In the example above, the username is john.
2. Password
The second field shows the user’s encrypted password. For security purposes, the passwords are kept in a separate file that is not readable to regular users. The /etc/shadow file stores user passwords in Linux.
Normally, the password field contains an x to show that the shadow file is storing the password securely. If the field is blank then the user does not need a password to log in. To maintain the overall system security, every user on your system should have a password. You can use the passwd command to change or manage user passwords in Linux.
3. User ID
The user ID field, commonly known as UID, is a number used by the Linux system to identify users. Most systems users have a user ID less than the number 1000 whereas regular users have IDs ranging from 1000 upwards. The root (administrative) user usually has the ID 0.
4. Group ID
The fourth field is for the group ID (commonly known as GID). As the user ID, the GID is also a number. The group ID determines the primary group of a user. In addition, GIDs categorize all users in specific sets for easier administration. A user can belong to more than one group in Linux. To find out more about which groups a user belongs to you can look at the /etc/group file.
5. GECOS
The next field is the GECOS field. It usually contains a user’s full name and additional details such as the phone number or room numbers, which are comma-separated. This field is optional and can therefore be blank.
6. Home Directory
This field contains the /home directory associated with the user. This is the primary directory that stores main user files and directories such as /Desktop and /Pictures. In this example, the user’s home directory is at /home/john.
Having separate home directories for each user is one of the factors that enables Linux to be a truly multi-user OS.
7. Shell
This field contains the name of the default shell associated with a user. The shell is the environment in which a user can run commands and scripts. Most Linux distros use the Bourne Again Shell (Bash) as the default shell program.
Making System Administration Easier on Linux
This guide has shown you what is the /etc/passwd file in Linux and the key role it plays when managing users on your Linux system. The passwd file contains user-related information such as the username, password details, home directory path, user and group IDs, etc.
As you have seen, most Linux users are usually part of a group to ease the administration of file access and other privileges. You can add users to groups yourself if you have the necessary permissions to do so.
