A. Remote Server Deployment and Installation
Remote access is identical to one of the technologies used to access a system through network media so that a user can configure a system, wherever it is as long as it is connected to the internet or network.
The types of applications commonly used in installing remote access on a server are SSH Server and Telnet. In general, Secure Shell (SSH) will run on the default port of 22.
Remote access can be categorized into 2, namely:
1. Desktop/GUI (Graphical User Interface)
Example: Remote desktop, VNC, and Radmin
2. Text
Example: Telnet, SSH, RAW, Rlogin, and Serial
1. SSH Server
SSH ( Secure Shell) is a protocol that allows users to control and modify the server remotely. SSH works in place of telnet, rlogin, ftp, and rsh. One of the main functions of SSH is to ensure security in transmitting data on a network
2. Open SSH Server Installation
For the ssh server application package the installation source is located on DVD 1 of the debian installation., the steps for installing SSH Server on the debian operating system are as follows:
Make sure the SSH Server installation source, namely dvd 1 debian, is registered in the repository.
Just check with the command:
nano /etc/apt/sources.list,
If you see the text
deb cdrom:[Debian GNU/Linux 8.5.0 _Jessie_ - Official amd64 DVD Binary-1 20160604-15:35]/ jessie contrib main
That means the debian system already recognizes the source of the dvd1 debiah installation, so the ssh server can already be installed. But if there is none, then you have to add the dvd 1 application source to the debian repository system, the method is:
1) Put dvd1 to cdrom.
2) Then type the following command
apt-cdrom add
then type the command again:
apt-get update
After confirming that the dvd1 installation source has been registered in the debian repository,
Then the next step you can install SSH Server for Remote Server.
The steps for installing ssh server in debian are as follows:
1) Put dvd source 1for ssh server installation
2) Type the following install command:
apt-get install open-ssh-server
Wait for the installation process to complete, it only takes a few seconds.
By default ssh servers that are already installed usually use port 22.
3. SSH Default Port Changes
The default SSH port attached is on port 22. The SSH default port can be replaced with another port. For example: 2233, 28, 88, or whatever.
The method is as follows:
1) Login to SSH by using putty
2) Type the command: nano /etc/ssh/sshd_config
# $OpenBSD: sshd_config,v 1.73 2005-12-06 22:38:28 reyk Exp$
# This is the sshd server system-wide configuration file. See
# sshd_config(5) for more information.
# This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin
# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented. Uncommented options change a
# default value.
#Port 22
#Protocol 2.1
Protocol 2
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress :
3) From the example above, you can simply notice the one I put red. You can simply replace "#Port 22" with "Port 88" if you want to change it to port 88. Like the example below:
# $OpenBSD: sshd_config,v 1.73 2005-12-06 22:38:28 reyk Exp$
# This is the sshd server system-wide configuration file. See
# sshd_config(5) for more information.
# This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin
# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented. Uncommented options change a
# default value.
Port 88
#Protocol 2,1
Protocol 2
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
Kemudian tekan tombol CTRL + X untuk menyimpan.
4) Lalu restart SSH dengan perintah : /etc/init.d/sshd restart
Pada Centos 7, silahkan ketikkan perintah berikut : service sshd restart
Atau perintah berikut : systemctl restart sshd.service
5) Muncul error :
Redirecting to /bin/systemctl restart sshd.service
Job for sshd.service failed because the control process exited with error code. See “systemctl status sshd.service” and “journalctl -xe” for details.
Silahkan buka dulu port 88 di firewall :
firewall-cmd –add-port 88/tcp –permanent
firewall-cmd –add-port 88/tcp
Lalu matikan selinux : nano /etc/selinux/config
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
# enforcing – SELinux security policy is enforced.
# permissive – SELinux prints warnings instead of enforcing.
# disabled – No SELinux policy is loaded.
SELINUX=disabled
# SELINUXTYPE= can take one of these two values:
# targeted – Targeted processes are protected,
# mls – Multi Level Security protection.
SELINUXTYPE=targeted
Lalu reboot agar selinux disabled : reboot
6) Tutup Putty Anda, lalu cobalah login lagi ke SSH dengan port 88.
B. Telnet
Telnet (Telecommunication network) adalah protokol aplikasi yang digunakan di Internet atau jaringan area lokal untuk menyediakan fasilitas komunikasi berorientasi teks interaktif dua arah menggunakan koneksi terminal virtual. Dengan kata lain dapat terkoneksi ke komputer lain dalam satu gedung, satu ruangan atau bahkan pada komputer di seluruh penjuru dunia.
Apa Kelebihan dan kekurangan menggunakan Telnet?
1) Kelebihan Telnet
Kelebihan menggunakan telnet adalah memudahkan pengguna untuk mengakses komputer dari jarak yang jauh.selain itu user interface yang cukup ramah, maksudnya pengguna dapat memberikan perintah dari jarak jauh (remote) jadi seolah-olah penggunanya mengeksekusi perintah pada command line pada komputer tersebut.
2) Kekurangan Telnet
Adapun kekurangan dari Telnet yaitu tingkat keamanan data dan program kurang baik yang memungkinkan pengguna NTLM authentication tanpa adanya enkripsi sehingga dapat memudahkan pencurian password yang dilakukan oleh sniffers, jika kita administrator sistem maka disarankan untuk menggunakan SSH pada Linux daripada Telnet Server untuk mengkonfigurasikan sistem kita.
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