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CentOS/RHEL 6

How to Install GUI for CentOS/RHEL 5,6,7

By admin

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

Filed Under: CentOS/RHEL 5, CentOS/RHEL 6, CentOS/RHEL 7, Fedora, Linux

Understanding Fencing in a Red Hat High Availability Cluster

By admin

The Basics A key aspect of Red Hat cluster design is that a system must be configured with at least one fencing device to ensure that the services that the cluster provides remain available when a node in the cluster encounters a problem. Fencing is the mechanism that the cluster uses to resolve issues and failures that occur. When you design your cluster services to take advantage of fencing, you can ensure that a problematic cluster node will be cut off quickly and the remaining nodes in the … [Read more...] about Understanding Fencing in a Red Hat High Availability Cluster

Filed Under: CentOS/RHEL 5, CentOS/RHEL 6, CentOS/RHEL 7, Fedora, Linux

How to configure VNC Server on Oracle Linux 6

By admin

Here is a short howto on configuring VNC server for Oracle Linux 6. 1. Check if the server is connected to Oracle Linux yum server Or ULN to avoid the dependency issue. # yum repolist 2. Install the vnc server RPMs: # yum install vnc* This installs latest version of RPMs: tigervnc-server-module, tigervnc and tigervnc-server. # yum install tigervnc-server-module tigervnc tigervnc-server 3. Edit the "/etc/sysconfig/vncservers" file to configure the required displays. The following … [Read more...] about How to configure VNC Server on Oracle Linux 6

Filed Under: CentOS/RHEL 6, Fedora, Linux, OEL 6

How to Access VNC Server Through A Web Browser in CentOS/RHEL

By admin

This post describes how to access VNC server which is already installed and configured on a CentOS/RHEL server: vnc-server for CentOS/RHEL 5 tigervnc-server for CentOS/RHEL 6 Before starting, it is assumed that the access the VNC console via vncviewer is possible: # vncviewer [Server IP]:5901 But the below message is received when tried to access using URL: http://[Server IP]:5901 over web broswer: RFB 003.008 The Steps VNC for HTTP access uses a port number other than the … [Read more...] about How to Access VNC Server Through A Web Browser in CentOS/RHEL

Filed Under: CentOS/RHEL 5, CentOS/RHEL 6, Fedora, Linux

How to Configure a script to execute during system shutdown and startup in CentOS/RHEL/Fedora

By admin

The script stop_cluster.sh should get executed during system bootup/shutdown. Email notification should be sent to confirm the execution of the script. If the script is placed in /etc/rc.d/ directory (For example /etc/rc.d/rc3.d/sample-testmail) it would not get executed because it is not a service started by SysV. Even if the script is moved to rc0.d it would be executed during the shutdown. To make SysV run a script, make it the SysV way, and for that merge the start script and stop script … [Read more...] about How to Configure a script to execute during system shutdown and startup in CentOS/RHEL/Fedora

Filed Under: CentOS/RHEL 5, CentOS/RHEL 6, Fedora, Linux

VNC server failed with “A VNC server is already running as :X” while vncserver restart

By admin

The Problem VNC server failed with "A VNC server is already running as :X" while vncserver restart. VNC server is not starting and getting the following error. # service vncserver restart Shutting down VNC server: 3:testuser 5:testuser2 [FAILED] Starting VNC server: 3:ctmagt70 New 'test1:3 (testuser)' desktop is test1:3 Starting applications specified in /tsc/apps/testuser/.vnc/xstartup Log file is /tsc/apps/testuser/.vnc/tscpinf001:3.log 5:testuser2 A VNC server is already running … [Read more...] about VNC server failed with “A VNC server is already running as :X” while vncserver restart

Filed Under: CentOS/RHEL 5, CentOS/RHEL 6, Fedora, Linux

How to Configure vncserver to start GNOME or KDE by default in CentOS/RHEL 5,6

By admin

By default, VNC starts up only a simple window manager and a terminal window. To enable a full Red Hat desktop environment over VNC, we need to configure vncserver to either start GNOME or KDE environments. Follow the steps outlined below to set a default desktop environment over VNC in a CentOS/RHEL 5,6 system. 1. Edit the file ${HOME}/.vnc/xstartup file to run gnome-session for GNOME or startkde for KDE instead of twm as shown below: - To start bare minimum desktop, use the below … [Read more...] about How to Configure vncserver to start GNOME or KDE by default in CentOS/RHEL 5,6

Filed Under: CentOS/RHEL 5, CentOS/RHEL 6, Fedora, Linux

How to configure NIS (Network Information Service) Master and Slave servers in CentOS/RHEL 5,6

By admin

What is NIS (Network Information Service) The Network Information Service or NIS (originally called Yellow Pages or YP) consists of a client-server directory service protocol for distributing system configuration data such as user and hostnames between computers on a computer network. NIS enables to create user accounts that can be shared across all systems over the network. The user account is created only on the NIS server. NIS clients verify the necessary username and password data from the … [Read more...] about How to configure NIS (Network Information Service) Master and Slave servers in CentOS/RHEL 5,6

Filed Under: CentOS/RHEL 5, CentOS/RHEL 6, Fedora, Linux

How to disallow or disable HTTP TRACE and TRACK requests in httpd (Apache)

By admin

My security team communicated that we are vulnerable to "Apache HTTP TRACE / TRACK Methods Allowed" issue, How to fix it? What is Apache TRACE and TRACK methods TRACE and TRACK are two HTTP methods used to debug web applications. These methods could be leveraged by malicious users to perform Cross-site Tracing attacks which are used to bypass authentication token protections. Disabling the TRACE and TRACK methods Add the line "TraceEnable off" if not already present to the httpd … [Read more...] about How to disallow or disable HTTP TRACE and TRACK requests in httpd (Apache)

Filed Under: Apache, CentOS/RHEL 6, CentOS/RHEL 7, CentOS/RHEL 8, Linux

How to audit all Commands run on a Linux system using auditd

By admin

The audit package ties into the Linux kernel audit subsystem. The audit system audits system calls and other kernel level events, not user-space events, so we need to audit the execve() system call which is what starts executing new programs. For the example in this post, we have taken the CentOS/RHEL system, but the steps remain more or less the same for other *NIX distributions as well. For CentOS/RHEL 7 Apply audit rules into the system 1. To keep the rules persistent after reboot or … [Read more...] about How to audit all Commands run on a Linux system using auditd

Filed Under: CentOS/RHEL 6, CentOS/RHEL 7, CentOS/RHEL 8, Fedora, Linux

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