SSH overview The SSH protocol (aka Secure Shell) is used to establish secure and reliable communications between two hosts. It supports different authentication methods and uses strong encryption to protect exchanged data. It is possible to use SSH-based communications instead of clear-text remote CLI protocols (telnet, rlogin) and unencrypted file transfer methods (such as FTP). It is also possible to use SSH for forwarding or tunneling a port, X forwarding, building VPN, as a SOCKS proxy and … [Read more...] about What is SSH? What are SSH authentication methods?
Linux
How to change the order of the authentication methods of ssh in CentOS/RHEL
Want to change the order of the authentication method that ssh tries while establishing a remote connection. How to change it? How to specify the order in which the client should try the protocol of authentication methods while establishing a connection with the remote host? Changing Order of Authentication Methods of SSH PreferredAuthentications is the option which specifies the order in which the client should try the protocol of authentication methods. This allows a client to prefer one … [Read more...] about How to change the order of the authentication methods of ssh in CentOS/RHEL
How to force the users to use both key and password with ssh in Linux
How to enable dual authentication in ssh? How to force the users to use both key and password with ssh while authenticating in Linux. By default, sshd will not force dual authentication. In order to force ssh for dual authentication follow the steps outlined below. For CentOS/RHEL6 Add following directive to /etc/ssh/sshd_config configuration file. # vi /etc/ssh/sshd_config RequiredAuthentications2 publickey,password To disable dual authentication for particular user, add on extra … [Read more...] about How to force the users to use both key and password with ssh in Linux
How to Setup a squid proxy server on CentOS/RHEL 7
Squid is a web proxy application with a variety of configurations and uses. Squid has a large number of access controls and supports different protocols, such as HTTP, HTTPS, FTP, and SSL. In this post, we will see how to use Squid as an HTTP proxy. The Setup A proxy server can be software or it can also be hardware, such as a bluecoat proxy. In this post, we will setup a proxy as software on a virtual device. The chosen software will be squid, but you can use a wide range of other … [Read more...] about How to Setup a squid proxy server on CentOS/RHEL 7
How to Disable Bluetooth in CentOS/RHEL 5,6,7
The Bluetooth kernel modules (bluetooth, bnep, btusb/hci_usb) are automatically loaded when the system boots and the Bluetooth service is enabled. The kernel modules can be prevented from being loaded by using system-wide modprobe rules. Blacklist Bluetooth modules Run the following commands to blacklist the Bluetooth modules, thus preventing them from loading if Bluetooth hardware is present. On CentOS/RHEL 5 and 6: # echo "install bnep /bin/true" >> … [Read more...] about How to Disable Bluetooth in CentOS/RHEL 5,6,7
How to Install Gnome Desktop Environment onto Oracle Linux 6.x
This document describes how to install Gnome Desktop environment onto an Oracle Linux 6.x system. The Stpes 1. On Oracle Linux 6.x, Gnome yum group is known as "Desktop", which was "Gnome Desktop Environment" on Oracle Linux 5.x. Thus, to install Gnome Desktop Environment on Oracle Linux 6.x use the below command: # yum groupinstall "Desktop" "Desktop Platform" "General Purpose Desktop" If the packages need to be re-installed, use the below command: # yum reinstall "@Desktop" "@Desktop … [Read more...] about How to Install Gnome Desktop Environment onto Oracle Linux 6.x
How to detect duplicate IP address on network in Linux
"Error, some other host already uses address" is printed when running 'service network restart' or 'ifup ethX' command on a CentOS/RHEL system. How to check for a duplicate IP address in the network? Using arping Command Run the arping command with the -D switch to enable Duplicate Address Detection. In the following example, substitute the address that you believe has been duplicated, and the interface that address is on. # arping -D -w 5 -I ethX IP.ADDRESS.TO.TEST # echo $? The 'echo … [Read more...] about How to detect duplicate IP address on network in Linux
How to Interpret and Analyze ‘sar’ Command Output in Linux
sar data is useful in pinpointing the system resource (networking, memory, IO, etc.) that is causing a performance issue. In addition, note that it contains much more data than is covered in this post; this is simply meant to highlight some of the areas that are useful in pinpointing system usage. Sar data contains several useful sections for determining how the system was performing at a given time. By default, this is configured to run at 10-minute intervals. Information on any of the … [Read more...] about How to Interpret and Analyze ‘sar’ Command Output in Linux
How to configure VNC (Virtual Network Computing) in CentOS/RHEL 5,6
Virtual Network Computing (VNC) works by capturing the display's frame buffer and making it available across the network. This recipe shows you how to install the basic VNC server and configure it to provide remote users access to their graphical desktop environment as if they were physically in front of the system. Installing the basic VNC service To install the prerequisite, run the appropriate command as root: For CentOS/RHEL 6: # yum install tigervnc-server tigervnc For … [Read more...] about How to configure VNC (Virtual Network Computing) in CentOS/RHEL 5,6
How to Install GUI for CentOS/RHEL 5,6,7
There are 2 possible paths to resolve the issue: Method A: Install the desktop related package groups after system install (Recommended) Method B: Select "Desktop" mode (Server with a GUI in RHEL 7) as the default installation mode Method A: Install the desktop related package groups after system install (Recommended) The following package groups need to be installed to boot a RHEL system into a graphical desktop environment with a recommended feature set: CentOS/RHEL 7 # yum … [Read more...] about How to Install GUI for CentOS/RHEL 5,6,7