Bussiness 19 December, 2023

Nohup: Maintains the execution of a command despite exiting the terminal

In the world of hosting and servers, it is essential to be able to execute commands remotely to manage our systems efficiently. A very useful tool that allows us to carry out this task is SSH (Secure Shell), a protocol that allows us to access a server securely and execute commands on it.

But what happens when we need to run a long, complex command or script that takes time to complete? What if we want to keep an SSH session open even after closing the terminal?

This is where Nohup comes in! In this article, we will explore how to use Nohup to maintain the execution of commands and even remote SSH sessions, allowing us to carry out tasks without interruptions or time limitations. Discover how to get the most out of this tool in your Linux projects and improve your productivity as a system administrator.

Run commands and scripts remotely with ssh

Running commands and scripts remotely over SSH is a key skill for every system administrator. With SSH, we can access a server from our local machine and execute commands as if we were physically on the remote machine. This gives us flexibility and efficiency when carrying out administrative tasks.

Executing simple commands over SSH is quite easy. We just need to open an SSH connection to the server using the “ssh” command followed by the username and IP address of the server. Once connected, we can enter the commands we want to execute directly in the terminal.

However, when we need to execute multiple commands on a remote computer, it can be tedious to have to type each command one by one after establishing the SSH connection. Luckily, there is a solution: we can create a file called "script.sh" that contains all the commands we want to execute in sequence and then send it to the server using SCP (Secure Copy).

Additionally, we can interact with the output of the remotely executed command thanks to the interactive capabilities of SSH. We can redirect this output to our local terminal to view it in real time and even save it to local files if we wish. This functionality allows us to monitor the results or record them for future analysis without problems.

Using SSH to execute commands and scripts remotely gives us flexibility and efficiency when managing our Linux systems. Whether performing simple or complex tasks, this powerful tool makes our daily work as server administrators easier.

Run simple commands remotely via SSH

To execute simple commands remotely via SSH, you simply need to access the remote server and use the ssh command followed by the username and IP address or domain of the server. Once you have successfully connected, you will be able to execute any command on the server as if you were working directly on it.

For example, if you want to check the operating system version on a remote server, you can use the following command:

ssh user@ip_address &;#39;lsb_release -a&;#39;

This will send the lsb_release -a command to the remote server and display the operating system version information. This way, you can execute simple commands without having to be physically present on the server.

Importantly, in order to use SSH to execute remote commands, you must have the appropriate permissions and know the credentials (username and password) or have an authorized public key to successfully authenticate to the remote server. Additionally, it is advisable to ensure that you have a stable Internet connection before logging in using SSH.

Run multiple commands on a remote computer using SSH

The ability to run multiple commands on a remote computer using SSH is a very useful feature for system administrators and developers. With this feature, we can quickly send a series of instructions to a server without having to manually connect and type each command separately.

To achieve this, we use the "&;amp;&;amp;" operator between each command we want to execute. For example, if we want to list the files in a remote directory and then copy them to another location, we can use the following format: "ls &;amp;&;amp; cp file1 file2". This way both commands will be executed sequentially on the remote server.

It is also possible to use curly braces "{}" to group multiple commands together. This can be especially useful when we need to perform several related actions within the same context. For example: "{command1; command2; command3}". The commands inside the braces are executed as a complete unit.

Additionally, if we need to execute multiple commands but are only interested in the output of the last command, we can use output redirection to save it to a file or local variable. This way we will avoid receiving unnecessary information during the execution of the script remotely.

Being able to run multiple commands on a remote computer using SSH offers flexibility and efficiency when managing servers or working with geographically distributed teams. This capability allows us to automate repetitive tasks and streamline our productivity as IT or software development professionals.

Execute commands remotely via SSH and interact with the output of the executed command

Executing commands remotely over SSH and interacting with the output of the executed command is a very useful skill in the world of server administration. With SSH (Secure Shell), users can access and control remote computers from their own terminal.

Once the SSH connection is established, simple commands can be executed on the remote computer. For example, we can check available disk space or list files in a specific directory. This allows you to perform basic tasks without having to be physically present on the server.

However, it is also possible to execute multiple commands sequentially or simultaneously using SSH. This makes it easier to perform more complex tasks and automate processes on multiple servers at the same time.

Additionally, when running a command remotely over SSH, it is possible to interact with the command output. This means that you can receive and respond to questions or requests generated by the executed command. This feature is especially useful for interactive scripts that require human intervention during execution.

Using SSH to execute commands remotely gives us flexibility and efficiency when managing servers from any location. Likewise, being able to interact with the command output allows us to automate complex tasks and maintain greater control over the processes carried out on remote computers.

Run commands remotely with a specific user

Executing commands remotely with a given user is common practice in server and operating system environments. This technique allows administrators to execute specific actions as root or any other user, without needing to log in directly to the remote machine.

To do this, the SSH (Secure Shell) tool is used, which allows establishing a secure connection between two computers and executing commands remotely. When connecting to the remote server using the ssh command, it is possible to specify which user will be used to execute the commands. This is done using the -l parameter followed by the desired username.

Once we are connected to the remote server with the indicated user, we can run any command or script that we have permission to use. For example, we could update operating system packages, restart specific services, or manage users and permissions.

It is important to note that in order to execute commands with a given user remotely, we must have the appropriate credentials (username and password) and the necessary permissions on the remote server. This ensures system security and prevents unauthorized access to sensitive resources.

Run a script from a local computer on a remote server

Running a script from a local computer on a remote server is a task commonly performed by system administrators and developers. This feature allows you to execute scripts or commands written on the local computer from the remote server terminal through the SSH protocol.

To perform this action, the "scp" (Secure Copy) command is used to copy the script file from the local computer to the remote server. Once the file is on the server, you can use another command called "ssh" to run that script remotely.

This process is extremely useful when you need to perform automated or repetitive tasks on multiple servers without having to connect to each of them individually. In addition, it also allows you to take advantage of the power and resources available on remote servers.

The ability to run scripts remotely provides flexibility and efficiency when managing multiple servers simultaneously. By using this method, administrators can easily control operations from their own local computer without having to constantly switch between different environments. It is a practical and convenient solution to improve productivity and optimize tasks within the field of hosting, VPS or any type of services based on Linux servers.

Run a script or command on multiple servers simultaneously

Executing a script or command on multiple servers simultaneously can be a tedious and time-consuming task if done conventionally. However, thanks to the use of SSH (Secure Shell), it is possible to automate this process and execute the commands on multiple servers at the same time.

One option to accomplish this task is to use the "parallel-ssh" command, which allows you to send commands to multiple servers in parallel. By using this command, you can specify a list of hosts on which you want to run the command or script.

Another option is to use tools like Ansible or Fabric, which are specially designed for remote administration and automation of deployment on different hosts. These tools allow you to define specific tasks through scripts and then execute them on multiple servers simultaneously.

In addition, there are more advanced options such as ClusterSSH, which allows you to open separate windows for each server and send commands to all of them at the same time. This makes remote management of multiple servers much easier.

Thanks to the use of SSH and specialized tools, it is possible to execute scripts or commands on several servers simultaneously, thus streamlining administrative tasks and optimizing the time spent on said work. This capability is especially useful when working with infrastructures made up of numerous geographically distributed teams.

Run long running scripts over SSH

Running long-running scripts over SSH can be very useful in different situations, especially when it comes to performing tasks that require a long time to complete. With SSH, it is possible to run these scripts on remote servers without having to maintain an active connection throughout the process.

A common way to run long running scripts is by using the nohup tool. This utility allows users to start a command or script and then log out without interrupting its execution. This means that even if we disconnect from the server or close the terminal, the script will continue to run until finished.

To use nohup, we simply need to precede our command or script with this keyword followed by the "&;amp;" symbol. For example:
```
nohup ./my_script.sh &;amp;
```

This way, we can leave our script running for hours or even days without worrying about losing the connection or accidentally stopping its execution. However, it is important to keep in mind that even if we are not directly viewing the script outputs in our terminal, they can be redirected to log files for later review.

Thanks to the proper use of nohup we can run long-running scripts over SSH without fear of unintentional interruptions due to accidental disconnections or shutdowns. This functionality is especially beneficial for tasks such as massive data processing, scheduled backups, or other complex operations that require significant time and resources to complete successfully.

Keep remote SSH sessions and processes running after disconnection

Understanding processes in Linux is essential to being able to maintain remote SSH sessions and processes running after disconnection. In an operating system, processes are the individual instances of programs that are currently running. Each process has its own unique identifier (PID) and can have different states, such as running, sleeping, or stopped.

There are several techniques to keep the SSH session running after disconnection. A commonly used option is to use the "nohup" command. This command allows a process to continue running even when the terminal from which it was started is closed. By using "nohup" followed by the name of the program or script to run, the process will continue running in the background, ignoring any SIGHUP signals sent to the terminal.

Another popular technique to keep remote SSH sessions and processes running after disconnection is to use the GNU Screen task manager. This tool provides a multiplexer interface that allows multiple virtual windows to be opened within a single SSH session. This means that even if you disconnect from the remote server, you can reconnect later and pick up exactly where you left off.

In addition to using "nohup" and GNU Screen, there are also other advanced ways to keep SSH sessions active even after disconnection. These include standard redirection (stdin/stdout/stderr) to specific files using ">" or "> >", as well as special settings within the ".ssh/config" file.

Understanding how processes work in Linux is key to being able to maintain remote SSH sessions and processes running after disconnection.

Understand processes in Linux

Understanding the processes in Linux is essential to have better control over the operating system and maximize its efficiency. In simple terms, a process in Linux refers to an instance of a program that is running. Every time you start an application or command in the terminal, a new process is created.

Each process has its own unique identifier called PID (Process Identifier). This allows the operating system to track and manage each of them individually. Additionally, processes can be related to each other through the process tree, where there is one main process and multiple subprocesses.

In Linux, these processes are classified into different states depending on what they are currently doing. Some common categories are: "Execution", when the process is active; "Wait", when waiting for some external action; and "Suspended", when the process is temporarily paused.

To get detailed information about the processes in real time, we can use commands like &;#39;top&;#39; or &;#39;ps&;#39;. These tools allow us to see useful information about each process, such as its resource consumption (CPU and memory), current state and ID of the owner user.

By understanding how processes work in Linux, we can optimize our use of the operating system and troubleshoot problems more easily. With this basic knowledge, we will be able to efficiently manage the applications and tasks that are running within our Linux-based server or VPS.

Techniques to keep SSH session running after disconnection

Keeping an SSH session running after disconnecting can be a necessity when working with remote servers. Fortunately, there are some techniques that can help achieve this and ensure that processes continue to work even if the connection is lost.

One option is to use the "nohup" command when running a process or command over SSH. This command allows the process to continue execution even if the terminal is closed or the SSH connection is lost. You simply add the prefix "nohup" before the command you want to execute, followed by the "&;amp;" symbol to send it to the background.

Another useful technique is to redirect both the input and standard output of the process using the "< /dev/null 2>&;amp;1" options. This ensures that there are no problems due to file descriptor changes during a disconnection.

You can also use additional tools such as "screen" or "tmux", which allow you to create multiplexed sessions and physically separate them from your original SSH connection. This way, you can reconnect later and resume your sessions without interruptions or data loss.

These techniques are very useful when you are working with remote servers and need to keep your sessions active even after closing your SSH connection. With them, you can ensure that ongoing processes continue to run smoothly until completion.

Questions tagged with [nohup]

Questions tagged with [nohup] are those that refer to the use of this command in the Linux operating system. It is not uncommon to find doubts related to its operation and its different applications. Users are looking to understand how to properly use nohup to keep a command or script running even after closing the terminal.

These questions can address a variety of concerns, such as how to use nohup to run remote commands over SSH, or how to keep remote SSH sessions and processes running after disconnecting.

It is important to note that the answers to these questions provide useful information about the correct use of the nohup command and offer practical solutions to the most common problems that may arise when working with it. Furthermore, by reading the questions tagged with [nohup], it is possible to learn new techniques and tricks to optimize its use and take full advantage of all its capabilities.

Questions tagged with [nohup] are an excellent source of knowledge and exchange of exexperiences on using the nohup command in Linux. By exploring these queries, users can expand their technical skills and discover new efficient ways to handle specific tasks using this powerful operating system resource.

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H2: Using the Nohup tool allows us to execute commands and scripts remotely via SSH without interruptions, keeping the session active even after disconnecting. This is especially useful in server or VPS environments where it is necessary to ensure that processes continue to execute.

Additionally, we have explored how to execute single and multiple commands on remote computers using SSH, as well as interact with the output of the executed command. We have also learned how to run scripts from a local computer on a remote server and how to perform this task simultaneously for multiple servers.

Lastly, we&;#39;ve discovered techniques to keep remote SSH sessions and processes running after disconnecting. This knowledge gives us greater flexibility and control over our Linux systems.

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