Software & AppsOperating SystemLinux

Why doesn’t my password work with useradd -p?

Ubuntu 10

In the world of Linux, creating and managing users is a fundamental part of system administration. A common command used for this purpose is useradd. However, a frequent issue that many encounter is that their password doesn’t seem to work when using the -p option with useradd. In this article, we’ll delve into the reasons behind this issue and provide solutions.

Quick Answer

The password doesn’t work with useradd -p because the -p option expects the password to be provided in an encrypted format, not plain text. To use the -p option correctly, you need to provide the encrypted version of the password. However, for security reasons, it is recommended to set the password interactively using the passwd command or use the adduser command for a more user-friendly approach.

Understanding the useradd Command

The useradd command is a utility in Linux used to create a new user or update default new user information. It’s a low-level utility often employed for adding users in batch. The syntax for the command is as follows:

useradd [options] username

The username is the name of the user to be added, and [options] are various parameters that can be used with the command. One such option is -p, which is used to set the user’s password.

The -p Option and its Misconceptions

The -p option allows you to set the password for the new user. However, there’s a common misconception that you can provide the password in plain text with this option. This is not the case. The -p option expects the password in an encrypted format, not plain text.

For example, if you use the following command:

sudo useradd -m -p password1 guest_user

You’re trying to create a user guest_user with the password password1. However, the -p option treats password1 as an encrypted password, not plain text. So, when you try to log in with the password password1, it doesn’t work because the system is comparing the encrypted version of your input with the string password1.

How to Use the -p Option Correctly

To use the -p option correctly, you need to provide the encrypted version of the password. You can use the crypt function in a programming language like Perl to generate this. Here’s an example:

sudo useradd -m -p $(perl -e 'print crypt($ARGV[0], "password")' 'encrypted_password') guest_user

Replace “encrypted_password” with the actual encrypted password you want to use. This command will create the user “guest_user” with the specified encrypted password.

Security Concerns and Better Alternatives

While using the -p option with an encrypted password can work, it’s not recommended. The password (or encrypted password) will be visible by users listing the processes, which is a security concern.

A safer alternative is to set the password interactively using the passwd command after creating the user. Here’s an example:

sudo useradd -m guest_user
sudo passwd guest_user

This will create the user “guest_user” and then prompt you to set a password for the user. This method is more secure as the password will not be visible on the command line.

Another user-friendly option is to use the adduser command:

sudo adduser --gecos '' guest_user

This command will create the user “guest_user” and prompt you to set a password and other user information.

Conclusion

In summary, when using the -p option with useradd, make sure to provide the encrypted password, not the plain text password. However, for security reasons, it’s recommended to set the password interactively using passwd or use adduser for a more user-friendly approach. Understanding these nuances of user management in Linux will help you maintain a more secure and efficient system.

Can I use the `-p` option with `useradd` to set a password in plain text?

No, the -p option expects the password to be provided in an encrypted format, not plain text.

How can I provide the password in an encrypted format with the `-p` option?

You can use the crypt function in a programming language like Perl to generate the encrypted password. For example: useradd -p $(perl -e 'print crypt($ARGV[0], "password")' 'encrypted_password').

Is it recommended to use the `-p` option with an encrypted password?

No, it is not recommended. The password (or encrypted password) will be visible by users listing the processes, which is a security concern.

What is a safer alternative to setting the password with the `-p` option?

A safer alternative is to set the password interactively using the passwd command after creating the user. For example: useradd -m guest_user followed by passwd guest_user.

Are there any user-friendly alternatives to `useradd` for creating users?

Yes, you can use the adduser command, which prompts you to set a password and other user information. For example: adduser --gecos '' guest_user.

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