rexec Command in Linux
The rexec command is a Linux utility designed to facilitate remote command execution. It enables users to execute commands on remote hosts seamlessly. Typically, rexec is part of the older rlogin suite of commands, which includes rsh and rlogin.
While rexec offers a convenient way to run commands on other machines, it is important to note that this utility transmits data, including passwords, in plain text. Therefore, it is not considered secure for sensitive operations.
Table of Contents
Here is a comprehensive guide to the options available with the rexec command −
Basic Syntax of rexec Command
The basic syntax for the rexec command is as follows −
rexec [options] host command
- host − The hostname or IP address of the remote machine.
- command − The command you want to execute on the remote host.
rexec Command Options
Listed below are few options that can be utilized with the Linux rexec command −
| Option | Description |
|---|---|
| -l username | Set the log-in name on the remote host to the specified username. |
| -p password | Provide the password for the remote account. |
| -n | Explicitly prompt for the username and password, even if provided in the environment, in the $HOME/.netrc file, or in the environmental variables REXEC_USER and REXEC_PASS. |
| -a | Do not set up an auxiliary channel for standard error from the command; the remote standard error and output are both returned on the local standard output. |
| -b | Use signal handling as in BSD rsh(1). Only the signals SIGINT, SIGQUIT, and SIGTERM are echoed to the remote process. |
| -c | Do not close remote standard input when local standard input closes. |
| -d | Turn on debugging information. The command sent to the remote host will be echoed. |
| -s | Do not echo signals received by rexec onto the remote process. |
Examples of rexec Command in Linux
Here are some practical examples to demonstrate how the command rexec can be used effectively −
- Basic Command Execution
- Specifying a Username
- Providing a Password
- Prompting for Username and Password
- Combining Options for Custom Behavior
- Debugging Connection
Basic Command Execution
Let's say you want to execute a simple command, such as ls, on a remote host. You can achieve this by running the following command −
rexec remotehost ls
This command will connect to the remote host specified by "remotehost" and execute the ls command. The ls command lists the contents of the current directory on the remote machine.
Specifying a Username
If you want to run the ls command on a remote host with a specific username, you can use the -l option as follows −
rexec -l john remotehost ls
In this example, the -l option is used to specify the username "john". The command will connect to the remote host as the user "john" and execute the ls command.
Providing a Password
To execute the ls command on a remote host using a specified username and password, you can use the -l and -p options −
rexec -l john -p mypassword remotehost ls
Here, both the -l option for the username "john" and the -p option for the password "mypassword" are used. The command will log in to the remote host as "john", using "mypassword" for authentication, and then execute the ls command.
Prompting for Username and Password
If you want to run a command on the remote host and explicitly prompt for the username and password, you can use the -n option −
rexec -n remotehost ls
The -n option will cause rexec to prompt the user explicitly for the username and password before executing the ls command on the remote host.
Combining Options for Custom Behavior
Let's say you want to use multiple options to customize command execution on a remote host. For example, you can prevent setting up a separate channel for standard error and execute the ls command as a specific user with a password −
rexec -l john -p mypassword -a remotehost ls
This example uses the -l option for the username "john", the -p option for the password "mypassword", and the -a option to prevent setting up a separate channel for standard error.
Debugging Connection
To execute a command with debugging information enabled, you can use the -d option −
rexec -d remotehost ls
The -d option turns on debugging information, which means the command sent to the remote host will be echoed.
Conclusion
The rexec in Linux is a versatile command for remote command execution, providing users with the ability to run commands on remote hosts seamlessly. However, due to its transmission of data, including passwords, in plain text, it is not suitable for sensitive operations.
By understanding the various options and examples provided in this guide, users can effectively leverage the rexec command for their remote execution needs.
Whether specifying a username, providing a password, prompting for credentials, or debugging connections, the rexec command offers a range of functionalities to customize and secure remote command execution.