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login – Log in to the system or switch user identities

The login command is used to log in to the system or switch user identities. It is commonly used to log in to a remote system via SSH or to switch user identities on a local system.

Overview

The basic syntax for the login command is:

login [options] [username]

If no username is specified, the login command will prompt for a username. Once a username is entered, login will prompt for that user’s password. If the password is correct, the user will be logged in.

If a username is specified on the command line, login will prompt for that user’s password without first prompting for a username.

To switch user identities, use the -p option to preserve the environment variables of the original user:

login -p username

This will log in as username while preserving the environment variables of the original user.

Examples

To log in as a specific user:

login john

This will prompt for John’s password and log in as John.

To switch user identities while preserving the environment variables:

login -p jane

This will prompt for Jane’s password and switch to Jane’s user identity while preserving the environment variables of the original user.

Options

The following options are available for the login command:

Option Description
-p Preserve the environment variables of the original user
-h Display help message and exit
-V Display version information and exit

Troubleshooting Tips

  • If you are unable to log in, make sure that you are using the correct username and password.
  • If you are logging in to a remote system via SSH, make sure that SSH is enabled on the remote system and that you are using the correct IP address or hostname.
  • If you are switching user identities and experiencing issues with environment variables, try using the -p option to preserve the environment variables of the original user.

Notes

  • The login command is typically used in conjunction with a terminal emulator to provide a command-line interface to the system.
  • The login command is often used to log in to a remote system via SSH, but it can also be used to switch user identities on a local system.

Related commands