What is Bastion Host in Linux?

What is Bastion Host in Linux?

A Linux bastion host is a powerful tool that allows administrators to control a lot of the security aspects of their Linux system. Bastion hosts are very important because they can be configured to restrict connections based on protocol, port number, and address. This article will cover what exactly a bastion host is, how it can help with your security configuration, and why you should use one for your company’s network.

What Is A Bastion Host in Linux?

A Linux bastion host is a computer that your network allows to access its resources, but no other computers are allowed to access. Administrators configure their bastions with only the ports and services needed for management, then lock down everything else so intruders can’t get through. Bastions can be configured using SSH or Telnet protocols, depending on which you have enabled on your machines.

Why Use a Bastion Host?

Bastion hosts help with Linux security because they restrict the amount of access your network has to them. For example, you can configure a server as a bastion host so that it’s accessible only from other servers on your network, and is completely locked down for everyone else. This helps reduce the risk of hackers getting into or spreading through your internal systems.

How do I Set up a Linux Bastion Host?

To set up a bastion host in your Linux environment, you need to complete the following steps:

  • Configure SSH or Telnet access on each machine that will be connecting to the bastion server. This is usually done when installing an operating system for servers in which it asks if you want to use password authentication instead of public/private keys.
  • Make sure all network services are disabled except for SSH or Telnet, and any other specific services needed by machines from outside sources. For example, Web Servers should only allow connections over port 80 (for unencrypted web traffic). If SSL is enabled, then port 443 would be used instead. Any other ports allowed through should not have service running on them unless they’re specifically needed.
  • Configure the SSH/Telnet daemon to only allow connections from specific source IP addresses on each machine that will be connecting to the bastion host, including other servers you want it to connect with. You can set this up in /etc/hosts.allow and /etc/hosts.deny files so everyone is restricted by default, but machines listed in hosts . allow are allowed access while those listed in hosts . deny cannot gain access unless they’re specifically added into an ALLOW rule.
  • The last step for setting up a Linux bastion host is creating rules allowing certain protocols or ports through for systems outside your network’s subnets (i.e., public internet traffic like Web Servers). You can use IPTables for this.

Here’s an example of how to set up a Linux bastion host using SSH:

  • /etc/hosts .allow : Allow access from specific hosts (i.e., connections coming in over the internet). In this case, our web servers would be allowed through on port 80 since that is their only service listening for outside connections. If SSL was enabled, then we could configure it here as well by adding port 443 instead of port 80.
  • ALL : Deny all other traffic except those mentioned above which are explicitly defined in /etc/hosts .allow file(s) . This means anyone else trying to connect will not have access unless are specifically added into either hosts . allow or hosts . deny files.
  • /etc/hosts .deny : Deny all other traffic. This means anyone connecting to the bastion host will not have access, even if they are listed in hosts . allow or any of its sub files (i.e., rules).

There are plenty of Linux distributions available which provide users with easy ways to set up their own server environment without having extensive knowledge about how they work under the hood. It’s also worth mentioning that not every distribution provides users with the ability to configure a bastion host, so it may be worth checking which ones support this type of configuration before committing yourself to one.

What Are Some Good Distributions for Setting up a Linux System as a Bastion Host?

Some popular choices that come immediately to mind are Ubuntu Server Edition and CentOS . The reason these two distributions are mentioned is because they’re stable environments that can hold up under heavy load without crashing. They also have extensive repositories available where you can download packages related to your server’s needs such as Apache web services or other tools required by the applications running on them. If you need an even more secure environment, Red Hat Enterprise Linux (RHEL) provides users who purchase subscriptions with all the benefits associated with using RHEL, which includes technical support.

What Are Some Of The Advantages?

One of the biggest advantages is that bastion hosts make it possible for administrators to manage user access, which is important for complying with new data security rules that are coming into place. It also makes it possible to create more secure networks by limiting the number of people who have physical access to your Linux systems and servers. Users can also work from home or on the road with their own systems by using a SSH connection to your server.

What Are Some Of The Disadvantages?

While bastion hosts are very useful, they do take up both processing power and memory in order to function properly. This is why it’s important that you choose an efficient system for this type of task because if the machine isn’t powerful enough then clients will have trouble connecting successfully. You should always make sure that all software is updated as well since outdated programs tend to be more vulnerable to attack than newer ones. Another disadvantage is that these types of servers restrict access based on protocol, port number, and address combination which means users must be aware of certain requirements before trying to connect.


Bastion hosts are powerful tools that can help secure your network by restricting access to certain resources on the server or database level. It’s also important to remember that they do have their downsides as well and may not be suitable for everyone depending upon how much effort you’re willing to put into maintaining them. Bastions should only be considered after implementing more conventional hardening techniques such as disabling root login through SSH, using TCP wrappers, or taking advantage of port knocking . If configured properly with these additional security layers in place, Linux bastion hosts will provide an excellent way of controlling traffic flow on your servers without requiring extensive knowledge of firewalls and IDS systems.

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