--- title: 'Setup SSHD Server and SSH Client on Linux' url: 'https://ra1ahq.blog/en/nastroika-servera-sshd-i-klienta-ssh-v-linux' markdown: 'https://ra1ahq.blog/en/nastroika-servera-sshd-i-klienta-ssh-v-linux.md' lang: en date: '2021-09-07' description: 'Sometimes you need to connect via SSH to your home or work PC to configure it. Instal' taxonomy: category: - blog tag: - Linux - управление archives_month: - sep_2021 archives_year: - '2021' --- # Setup SSHD Server and SSH Client on Linux 7 September 2021 15:13 ### Setup SSHD Server and SSH Client on Linux [Linux](https://ra1ahq.blog/en/tag:Linux), [управление](https://ra1ahq.blog/en/tag:%D1%83%D0%BF%D1%80%D0%B0%D0%B2%D0%BB%D0%B5%D0%BD%D0%B8%D0%B5) 7 September 2021 15:13 Sometimes you need to connect via SSH to your home or work PC to configure it. ### Installation plan 1. Install SSHD on a production Ubuntu Linux server. 2. Configure SSHD on the server. Instead of the default TCP port 22 for the SSH service, in this example we will use port 22334. 3. The SSHD server must be up and running constantly. Allow the SSHD service to start. 4. The local UFW firewall must be configured to allow external access to port 22334/TCP. 5. If you plan to connect from the Internet, you must forward from the WAN port of the router, port 22334, to the IP address of the computer on the local network. 6. Install SSH on MX Linux client (Debian 11 "Buster" or Debian 12 "Bookworm") 7. Connect via SSH from the client to the server. At the end of the article I touched on X11-forwarding. ### Step 1. Install SSHD on the server Installing SSHD on Ubuntu Linux - the parameters of the apt-get command specify the name of the ssh meta package: ``` sudo apt-get install ssh ``` This command will install packages `openssh-client` and `openssh-server` at the same time. ### Step 2. Setting up an SSHD server Setting up SSHD on a computer to which we connect externally First I copy to bak, i.e. I put aside the original SSHD configuration file: ``` sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.COPY ``` Correcting the configuration file [according to instructions](https://itproffi.ru/ustanovka-i-nastrojka-servera-ssh-v-linux/) taking into account that login will be carried out using a password. I fixed it using the "nano" editor: ``` sudo nano /etc/ssh/sshd_config ``` My config file **sshd\_config** I quote below (you can copy and paste it): ``` cat /etc/ssh/sshd_config | grep \#-v ``` `Include /etc/ssh/sshd_config.d/*.conf` `Port 22334` `AddressFamily inet` `ListenAddress 0.0.0.0` `PermitRootLogin no` `MaxAuthTries 6` `MaxSessions 1` `PasswordAuthentication yes` `PermitEmptyPasswords no` `ChallengeResponseAuthentication no` `UsePAM yes` `X11Forwarding yes` `X11DisplayOffset 10` `PrintMotd no` `AcceptEnv LANG LC_*` `Subsystem sftp /usr/lib/openssh/sftp-server` ### Step 3: Configuring the SSHD Service to Start on Ubuntu Server The SSHD service is used on the server for remote administration of the server and for connecting to it from the outside. Allowing the SSHD service to run continuously when the operating system boots - by service name ssh.service: ``` sudo systemctl enable ssh ``` Restarting the sshd daemon to apply changes to the configuration file on the server (host PC). ``` sudo systemctl restart ssh ``` The service name is one - ssh. The name sshd is an alias. If you access the ssh service by name `sudo systemctl enable sshd.service` - the command will not work (error *"Failed to restart sshd.service: Unit sshd.service not found."*). Because the main service is called `ssh.service` and its alias is `sshd.service`. Conclusion: The ssh service name is used to manage the sshd service. The commands `sudo systemctl restart ssh` and `sudo systemctl restart sshd` they do the same thing, but the first one is preferable. ### Step 4: Configure the local UFW firewall Start and allow ufw to start after reboot, with one command. ``` sudo systemctl enable --now ufw ``` Check: ``` sudo systemctl status ufw ``` To open the "secret" port 22334 of the sshd server on the firewall, I ran a command that adds an allow rule: ``` sudo ufw allow 22334 ``` View ufw firewall rules: ``` sudo ufw show added ``` ### Step 5. Port forwarding Since I tested the task inside the local network, I skip this point. Anyone can configure forwarding a “secret” SSH port on an Internet router independently. If a VPN tunnel is used, port forwarding, which is obvious, is not necessary. ### Step 6. Install ssh on a netbook running MX Linux (Debian) On Debian, the ssh installation command is slightly different than on Ubuntu: ``` sudo apt-get install ssh ``` ### Step 7. Connect to the SSH server from the client If the server has a static "white" IP address, connecting to it from the client is performed with the command ``` ssh user@123.45.67.8 -p 22334 ``` where user is the user login that must exist on the server, 123.45.67.8 - server IP address, 22334 - SSH port. When you connect for the first time, there will be a message about trust in the server, answered “*yes*” from the keyboard. Then you need to enter **password** to your account **user**, and you will be taken to the server console (terminal session). If the server key/certificate has changed (for example, the OS has been reinstalled), then the message “WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED” will appear and the connection will not occur. If you are sure that everything is in order with the machine, the server has simply been reinstalled, perform *on the client* removal of the old server certificate fingerprint (fingerprint), with the command that will be written in the message, for example:`ssh-keygen -f "/home/user/.ssh/known_hosts" -R "\[123.45.67.8\]:22334`. ### Bottom line *Setting is complete.* Login to the remote server via SSH is completed. ### Next steps If you plan to frequently connect to the server from the same machine, instead of password protection, you can configure a connection to the SSH server using certificates generated by the "ssh-keygen" program, as described in [article itproffi.ru](https://itproffi.ru/ustanovka-i-nastrojka-servera-ssh-v-linux/). ### Solving the problem with X11 Forwarding *(Addendum dated November 15, 2023).* After following the instructions, I gained access to the server in ssh text mode, but it was not possible to work from the client terminal in *X11 forwarding* mode (ssh -X ...) and then when running graphical server applications on the client, for example, when launched from an ssh session `xclock` an error occurred **"connect localhost port 6000: Connection refused. Error: Can't open display: localhost:10.0"**. This problem is not solved in any way in the client terminal. I got it like this: **On the client:** ``` sudo apt install putty ``` Then - **Start - Internet - Putty SSH Client** - **"Configuration" -** connection **-** SSH **-** enable compression\*\* - **"Configuration" -** connection **-** SSH **-***X11***-***Enable X11 forwarding*\*\* - **"Configuration" -** "Session"\*\*- entered the IP address and port of the server - **"Configuration" -** "Session" **-** saved sessions **-My-** save\*\* - selected **My** - pressed **"Open"** - entered username and password - got into the server session - check:`echo $DISPLAY` - this command should output `localhost:10.0`. (If this is not the case, run the command `export DISPLAY=:10.0`) - `xclock` - xclock started on the client screen (running on the server)! Hurray! - `sudo apt install xsysinfo` - `xsysinfo`- information about the server core load in real time. --- **Links**: - [Description of options in the sshd\_config configuration file](http://www.faqs.org/docs/securing/chap15sec122.html) ### Related publications [ ![](https://ra1ahq.blog/images/6/8/1/3/3/68133cc0ab7ddf32ba1a9c7eaeef3a6fa562e88f-msg.png) Tox Messenger ](https://ra1ahq.blog/en/tox-messenger) [ ![](https://ra1ahq.blog/images/f/3/a/2/c/f3a2c07ef5b32c0308ab703405a5a5ca87b75283-archer-ac600-728.webp) Installing the kernel driver for the TP-Link Wi-Fi adapter after updating the Debian OS ](https://ra1ahq.blog/en/ustanovka-draivera-yadra-dlya-wi-fi-adaptera-tp-link-posle-obnovleniya-os-debian) [ ![](https://ra1ahq.blog/images/d/2/5/c/7/d25c7282750b398f71041fb8b90640b692e7e4b8-decibelfmtitle.png) Linux Cinnamon Desktop Applets for Listening to Internet Radio Stations ](https://ra1ahq.blog/en/applety-dlya-rabochego-stola-linux-cinnamon-dlya-proslushivaniya-internet-radiostancii) [ ![No picture](https://ra1ahq.blog/user/themes/mytheme/images/no-image.png) Passing a parameter to a Linux module/driver ](https://ra1ahq.blog/en/peredacha-parametra-modulyu-draiveru-linux) [ ![](https://ra1ahq.blog/images/5/c/4/e/a/5c4ea9c8c3f0b4dd890116d8fe7cbadfdb9814ba-archer-ac600.webp) Installing the TP-Link Archer T600U Nano Wi-Fi adapter driver in Debian 13 "Trixie" ](https://ra1ahq.blog/en/ustanovka-draivera-wi-fi-adaptera-tp-link-archer-t600u-nano-v-debian-13-trixie) [ Backward](https://ra1ahq.blog/en/pro-obnovlenie-debian-10-buster-do-11-bullseye "Previuous page") [ Forward ](https://ra1ahq.blog/en/testirovanie-skorosti-peredachi-dannykh-s-pomoshyu-ssh-i-iperf "Next page") ## Languages - 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