


How to configure highly available remote logins (such as SSH and Telnet) on Linux
Jul 05, 2023 am 11:10 AMHow to configure high-availability remote login (such as SSH and Telnet) on Linux
Abstract: Remote login is one of the most commonly used functions in Linux systems, which allows us to connect to remote hosts through the network and operate. In practical applications, in order to ensure system availability and security, the remote login service needs to be configured in high availability mode. This article will introduce how to configure highly available remote login on Linux, including SSH and Telnet, and provide relevant code examples.
1. SSH configuration
SSH (Secure Shell) is a remote login protocol based on encryption technology. Secure remote login can be achieved through SSH in an unsecured network. The following are the steps to configure SSH high availability:
- Install and configure SSH server
In Linux systems, the commonly used software package for SSH servers is OpenSSH. First, we need to ensure that the OpenSSH package is installed on the host machine.
$ sudo apt-get install openssh-server # Ubuntu/Debian
$ sudo yum install openssh-server # CentOS/RHEL
After the installation is completed, the SSH server will automatically Starts and listens on the default port 22.
- Configure SSH communication key
In order to achieve high availability, we can use an SSH communication key pair for authentication instead of using the traditional username/password.
First, we need to generate an SSH key pair:
$ ssh-keygen -t rsa
Then, copy the public key to all remote hosts:
$ ssh-copy-id remote_host
- Configuring SSH load balancing
In order to achieve high availability of SSH, we can use load balancing to distribute remote login requests to multiple on a host. Commonly used load balancing software include HAProxy and Nginx.
Taking HAProxy as an example, first install HAProxy:
$ sudo apt-get install haproxy # Ubuntu/Debian
$ sudo yum install haproxy # CentOS/RHEL
Then, edit the HAProxy configuration file:
$ sudo vi /etc/haproxy/haproxy.cfg
Add the following configuration block in the file:
frontend ssh
bind *:22 mode tcp default_backend ssh_servers
backend ssh_servers
mode tcp balance roundrobin server ssh1 192.168.1.101:22 check server ssh2 192.168.1.102:22 check server ssh3 192.168.1.103:22 check
Save and exit the file, then restart the HAProxy service:
$ sudo systemctl restart haproxy
Now you can use HAProxy to provide IP address to connect to the SSH server.
2. Telnet configuration
Telnet is a protocol used for remote login, but it does not have the encryption function like SSH, so it is not suitable for use in insecure networks. The following are the steps to configure Telnet high availability:
- Install and configure Telnet server
In Linux systems, the commonly used software package for Telnet servers is telnetd. First, we need to ensure that the telnetd package has been installed on the host (example: CentOS/RHEL):
$ sudo yum install telnet-server
After the installation is complete, the Telnet server will Starts automatically and listens on the default port 23.
- Configuring Telnet Load Balancing
Similar to SSH, we can use load balancing to achieve high availability of Telnet. In Linux, we can use iptables and netfilter to achieve load balancing.
First, edit the iptables configuration file:
$ sudo vi /etc/sysctl.conf
Add the following configuration at the end of the file:
net.ipv4.ip_forward = 1
Save and exit the file, then load the configuration file:
$ sudo sysctl -p
Next, execute the following command to configure load balancing :
$ sudo iptables -t nat -A PREROUTING -p tcp --dport 23 -j DNAT --to-destination
$ sudo iptables -t nat -A POSTROUTING - j MASQUERADE
Where,
- Configuring Service Discovery
In order to achieve high availability, we need to find a way to distribute client requests to multiple Telnet servers. Commonly used service discovery software include ZooKeeper and Consul.
Taking ZooKeeper as an example, first install ZooKeeper:
$ sudo apt-get install zookeeperd # Ubuntu/Debian
$ sudo yum install zookeeper # CentOS/RHEL
Then, edit the ZooKeeper configuration file:
$ sudo vi /etc/zookeeper/conf/zoo.cfg
Add the following configuration to the file:
server. 1=zoo1:2888:3888
server.2=zoo2:2888:3888
server.3=zoo3:2888:3888
where zoo1, zoo2, and zoo3 are the host names of the ZooKeeper server .
Save and exit the file, then restart the ZooKeeper service:
$ sudo service zookeeper restart
Now you can connect to the Telnet server using the IP address provided by ZooKeeper.
Conclusion
By configuring a highly available remote login service, we can ensure the availability and security of the system. This article describes how to configure high availability of SSH and Telnet on Linux and provides relevant code examples. I hope this article can be helpful to you, thank you for reading!
The above is the detailed content of How to configure highly available remote logins (such as SSH and Telnet) on Linux. For more information, please follow other related articles on the PHP Chinese website!

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