Recently my son started to spend more time on Facebook. How much ever I tell him, he still uses it whenever I wasn’t at home. So I desperately wanted a quick trick to block Facebook on Windows (better if I can do it without installing a software) and here’s how it’s done. All…
If you are stuck with an error “Service n-net is not running” while installing OpenStack using Devstack, then here’s how you can fix the issue. +functions-common:service_check:1674 echo ‘Error: Service n-net is not running’ Error: Service n-net is not running +functions-common:service_check:1677 ‘[‘ -n /opt/stack/status/stack/n-net.failure ‘]’ +functions-common:service_check:1678 die 1678 ‘More details about…
With the appropriate permissions, the user can launch VM on a specified host/compute node in OpenStack Mitaka. All you need to do is to use –availability_zone zone:host argument while executing openstack server create command as shown below: $openstack server create –image –flavor m1.tiny –key_name test –availability-zone nova:compute3 In order to perform this operation, you need to…
I recently installed OpenStack Mitaka on my test bed and imported few images from CentOS & Ubuntu repositories. Once the VM is booted, I tried to login through VNC console. Unfortunately, I didn’t knew the username and password and the information was not available on the page where the image was downloaded…
Question: I wanted to install a package as a local user and use sudo wherever required. To do that, I created an account called ‘stack’ and made the below entry in my /etc/sudoers file. # User privilege specification root ALL=(ALL:ALL) ALL stack ALL=(ALL) NOPASSWD:ALL However, when verified through command line using…
During one node installation of OpenStack Kilo, I tried creating a tenant and the keystone service failed with an error as shown below: root@cloudsec1:/usr/share/openstack/cloudgear# keystone tenant-create –name admin –description ‘Admin Tenant’ –enabled true |grep ‘ id ‘|awk ‘{print $4}’ Traceback (most recent call last): File “/usr/bin/keystone”, line 6, in from…
I need to install Ubuntu on my rack server which didn’t come with the CD-ROM drive, but had USB ports on it. Hence, I decided to create a bootable pendrive and install Ubuntu from it. There are a lot of solutions available to achieve this. But I will show you the quickest and…
Generally HTML pages can contain links that can target to PDF file and when clicked, the browser opens the PDF file starting from the first page. Well that’s the default behavior, but I wanted to create a link in HTML page and that should point to a particular page in a…
I have been using OpenCA for managing a certificate authority and only to be shocked when it broke last night. All of a sudden, the OpenCA startup script failed with an error message as shown below. Undefined subroutine &Scalar::Util::blessed called at /usr/lib/perl5/5.8.8/overload.pm line 89. Compilation failed in require at ./openca_start line 62. It…
Previously we have seen the installations of hypervisors like Xen and cloud middleware like openstack. Recently a new technology called docker container has become the hottest trend in application development. In this article we shall see the what exactly is a docker, its differences with virtual machines, installation of docker and its…
Hping is a command line TCP/IP packet assembler/analyzer with embedded Tcl scripting functionality. Inspired by the ping command, Hping was developed by Antirez in 1998. As the name suggest, hping isn’t only able to send ICMP echo requests, but supports TCP, UDP, ICMP and RAW-IP protocols, has a traceroute mode,…
Question: In my CentOS 5 VM (running on Xen server), the date command displays wrong output (as 16 Jun 2015 07:05:11 instead of 16 Feb 2016 13:07:00). I tried to sync date via ntpdate command without success and setting the date manually via the date command didn’t work as well. Below is the message obtained from…
A bridge is a device that separates two or more network segments within one logical network. A bridge is one step above the Hub (by default, a Linux bridge acts as a Switch) – it reviews the destination of the packet before sending. If the destination address is not on…
Question : Recently installed minimal version of CentOS 7 as a guest VM on my xen hypervisor. After successful completion of the installation, executed ifconfig command to know the network devices and the addresses allocated. But to my surprise got the below error: [root@localhost]# ifconfig -bash: ifconfig: command not found…
Monitoring network connectivity is an important part of server administration. Few tools like ping, traceroute are simple to use and provides valuable information. Today, I’ll show you another powerful diagnostic tool called MTR which combines the functionalities of traceroute and ping programs. MTR stands for My Traceroute – it allows you to investigate…
Question: I followed your tutorial – how to identify the DNS server IP address configured on my CentOS 6 using the dig command and ran into an error as shown below: -bash: dig: command not found Well, the error was clear. So I tried to install dig via yum as shown below: [root@cloud2…
I used rsync command to copy a particular user directory from one storage device to another. The operation completed successfully without throwing any warning/error. But to my surprise, the data to be copied was around 167GB and the copied data was of just 1.4GB! I used ‘du’ command to calculate the disk size…
Recently due to some issue I had to re-install Windows 10 OS on my Lenovo Ideapad laptop. The installation went on well and the system came up. But then observed that booting of the OS was taking a lot of time, and once booted completely the system was quite slow….
Sticky Notes, a simple app which comes bundled with Windows 10/8/7 is a powerful reminder visible on your screen to help you plan your day, of course it doesn’t do a lot. These sticky notes is not for detailed note taking, instead you can find may other apps something like…