Linux Blimp

We’ve previously written about good open source software that batch converts image files. Batch conversion offers lots of benefits. Batch image converters let you process hundreds or thousands of images with a few clicks or even a single command. By optimizing image files that are displayed on websites, bandwidth is conserved, storage space is conserved, and sites load faster, which will help to provide a better end user experience.

The last time we surveyed the scene (article: Save Time and Effort with these Excellent Batch Image Processors) there was a fairly limited range available to recommend. But I want to recommend a further utility. It’s called imgp, a Python-based command-line tool that lets you resize and rotate JPEG and PNG files. The software can resize (or thumbnail) thousands of images with a single command. The software is a standalone utility, it’s not tied to a file manager or other software.

imgp was previously called imgd.

Installation

Packages for Arch Linux, CentOS, Debian, Fedora, openSUSE Leap and Ubuntu are available.

If your distribution doesn’t carry the latest version, you can clone the software’s GitHub repository.

git clone https://github.com/jarun/imgp.git
cd imgp

You can copy the imgp file into a directory in your PATH. There’s nothing to compile. imgp requires Python 3.5 or later.

In operation

If you type imgp at a shell, the software outputs the various flags that are available. There’s a pretty good range available with this tool.

The output below shows imgp in action, resizing a directory of png files that are at least 50KB in size.

Features of imgp include:

• Resize by percentage or resolution.
• Rotate clockwise and anti-clockwise by specified angle.
• Adaptive resize considering orientation.
• Brute force to a resolution.
• Optimize images to save more space.
• Limit processing by minimum image size.
• Nearest neighbor interpolation for PNG files – a simple method of multivariate interpolation in one or more dimensions.
• Convert PNG images to JPEG format.
• Support for progressive JPEG files, images created using compression algorithms that load the image in successive waves until the entire image is downloaded. The website visitor perceives the image loads faster as they see the whole image straight away.
• Erase exif metadata. This metadata contains information about the device that took the picture, the dimensions of the image and, when available, GPS coordinates identifying the location where the picture was taken.
• Specify output JPEG image quality.
• Force smaller to larger resize.
• Process directories recursively. If you need to convert a lot of images in nested directories, this option is a massive time saver.
• Overwrite source image option.
• Completion scripts for bash, fish, zsh.
• Identifies Multi Picture Object (MPO) files, a multi-image extension of the JPEG image format. This extension is often used for stereoscopic images.
• Minimal dependencies.

Summary

If you need to process a bunch of PNG or JPEG files, imgp is a handy utility.

Arun Prakash Jana is notable for coding other useful open source software. In particular, I’m a regular user of his nnn, a fast console based file manager, and googler, a console based utility tool to Google from the command-line.

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Whonix is an open source Linux operating system built around the popular Tor anonymity network software and based on the well known Debian GNU/Linux distribution. It allows users to install a secure, general purpose and anonymous Linux-based operating system that runs entirely in the VirtualBox virtualization software. It is distributed as gateway and workstation editions.

It’s distributed as OVA files

The developers doesn’t provide regular ISO images for their Linux distribution. Instead, only OVA (Open Virtualization Format) files are available for download, which can be imported into the VirtualBox application. To import the OVA file, you will need to go to the File menu and select the Import Appliance option. Next, you will be able to browse to the location where you saved the OVA file and import it (the import process will take a long time, because the application needs to create a new disk image).

Provides various attractive features

It is important to know that before you import the OVA file, VirtualBox will ask you to change various settings. Do not change anything on this step, just click the Import button. After importing, you can fire up the Whonix virtual machine as you normally start your other VMs. The system provides various attractive features, such as anonymous IRC, anonymous publishing, and anonymous email through TorBirdy and Mozilla Thunderbird. It allows users to add a proxy behind Tor, torify almost any application, and circumvent censorship.

Supports only the 32-bit architecture

Whonix also supports DNSSEC (Domain Name System Security Extensions) over Tor, encrypted DNS, full IP/DNS protocol leak protection, and transparent proxy. Additionally, user will be able to tunnel Freenet, I2P, JonDonym, Proxy, Retroshare, SSH, UDP and VPN through Tor, as well as to enforce Tor. It supports only the 32-bit (486/686) architecture. The Workstation edition uses the KDE desktop environment and include open source applications like the Iceweasel web browser, XChat IRC, Tor Browser, and many more.

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WebKitGTK+ is a completely free, versatile, powerful and open source command-line software that aims to port the powerful WebKit rendering engine to the GTK+ GUI toolkit and, of course, the GNOME graphical desktop environment.

The project incorporates WebKit’s full functionality through a set of GObject-based APIs (Application Programming Interfaces), and it is suitable for applications that require any type of web integration, from mature web browsers to hybrid HTML/CSS apps.

Used in Epiphany, Midori, and other powerful apps

WebKitGTK+ is successfully used in popular and powerful applications that work under the GNOME desktop environment or require the GTK+ toolkit, such as the Epiphany and Midor web browsers.

The project is very useful on both desktop and embedded systems, it supports WebKit2, and allows developers to easily build applications that rely on the web platform for increased responsiveness and security.

Uses process separation to support GTK+2 plugins on GTK+3 apps

Another interesting feature is process separation, which is used by WebKitGTK+ to seamlessly support plugins that are written in the 2.x branch of GTK+, such as Adobe Flash Player, in GTK+3 apps.

In addition, WebKitGTK+ offers full support for video and audio streams in web pages through the GStreamer WebKit backend, supports the HTML canvas element, supports WebRTC and WebAudio technologies, as well as accelerated rendering and 3D CSS.

Under the hood

Among WebKitGTK+’s runtime requirements (be aware that the list will change in time, as the project evolves), we can mention GTK+ 3.6.0 or later, gail 3.0 or later, GLib 2.36.0 or higher, libsoup 2.42.0 or later, Cairo 1.10 or higher, Pango 1.30.0 or higher, libxml or later 2.6, fontconfig 2.5 or later, FreeType2 or higher 9.0, and libsecret.

Moreover, depending on your configuration options WebKitGTK+ may also require GObject introspection 1.32.0 or higher, libxslt 1.1.7 or later, SQLite 3.0 or later, GStreamer 1.0.3 or higher, gstreamer-plugins-base 1.0.3 or later, Enchant 0.22 or later, Clutter, as well as Clutter GTK+.

Rendering engine WebKit GTK+ GNOME WebKit WebKit GTK+ Rendering Engine

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The terminal is a very powerful tool, and it’s probably the most interesting part in Unix. Among the plethora of useful commands and scripts you can use, some seem less practical, if not completely useless. Here are some Bash commands that are fun, and some of them are useful as well.

Oneko

This command adds some spice to your terminal by adding a cat to your screen which will chase after your (mouse) cursor. Install it by running this script:

Type oneko to display the cat.

figlet

Figlet is a command for those who love to write in ASCII art. It greatly simplifies this task as it automatically transforms any given string. It comes with a bunch of fonts by default at “/usr/share/figlet/fonts/,” and you can of course add your own.

figlet [-f path to the font] [string]

Read more at MakeTechEasier

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When you start learning data science, often your biggest worry is not the algorithms or techniques but getting access to raw data. While there are many high-quality, real-life datasets available on the web for trying out cool machine learning techniques, I’ve found that the same is not true when it comes to learning SQL.

For data science, having a basic familiarity with SQL is almost as important as knowing how to write code in Python or R. But it’s far easier to find toy datasets on Kaggle than it is to access a large enough database with real data (such as name, age, credit card, social security number, address, birthday, etc.) specifically designed or curated for machine learning tasks.

Wouldn’t it be great to have a simple tool or library to generate a large database with multiple tables filled with data of your own choice?

Aside from beginners in data science, even seasoned software testers may find it useful to have a simple tool where, with a few lines of code, they can generate arbitrarily large data sets with random (fake), yet meaningful entries.

For this reason, I am glad to introduce a lightweight Python library called pydbgen. In this article, I’ll briefly share some information about the package, and you can learn much more by reading the docs.

What is pydbgen?

Pydbgen is a lightweight, pure-Python library to generate random useful entries (e.g., name, address, credit card number, date, time, company name, job title, license plate number, etc.) and save them in a Pandas dataframe object, as an SQLite table in a database file, or in a Microsoft Excel file.

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Fedora is the best desktop Linux distribution for many reasons. Not only is it fast and reliable, but it is constantly kept up to date with fairly bleeding edge packages. Not to mention, it uses the greatest desktop environment, GNOME, by default. Most importantly, it respects and follows open source ideology. It is a pure Linux and FOSS experience that is an absolute joy to use. It’s no wonder Linus Torvalds — the father of Linux — chooses it.

With all of that said, Fedora didn’t get great overnight. It took years of evolution to become the exceptional operating system it is now. In fact, today, we celebrate the Linux distribution’s 15th birthday! Yes, it was way back in 2003 when Fedora Core 1 was released to the world, forever changing the course of history for the better.

If you are feeling fairly nostalgic, the original announcement is archived, and you can view it here. Even better, the Fedora Project has created a Fedora Core 1 virtual disk image so you can easily try the retro operating system yourself! You simply load it into GNOME Boxes and you’re off to the races. What a great way to celebrate the 15th birthday, right? You can download the image here.

Link Dupont of the Fedora Project shares the following about the aforementioned virtual disk image.

Fedora is proud of its heritage. There is no better way to understand history than to experience it. Fortunately, modern virtualization software ships with Fedora Workstation by default! So why not try out Fedora Core 1 yourself? We’ve put together a virtual disk image of Fedora Core 1 (927 MB download) that can be imported directly into GNOME Boxes. It even points to the “current” update repositories so you can try out the “new” yum package manager yourself.

Whether you are currently using the excellent Fedora 29 or some other distro like Ubuntu, Manjaro, or Arch, you absolutely owe Fedora a debt of gratitude for all it has contributed to both the Linux and open source communities over the years. As the distribution enters a new chapter following the Red Hat acquisition by IBM, I hope and pray for another 15 years. Happy Birthday, Fedora!

Are you a fan of Fedora? Please tell me your fondest memories of the distribution in the comments below.

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GNOME is a complex and sophisticated desktop environment that can be used on any Linux distribution, on top of a window server, such as X11 or Wayland. It is a 100% free and open source project. It can be described in many ways, but the most important things to know when talking about GNOME is that it is usable, accessible, customizable, international, user-friendly, organized, supported, intuitive and very attractive.

The GNOME development platform

The GNOME development platform is also an important part of the GNOME desktop environment, providing an extensive, developer-friendly framework for building applications that integrate into the rest of the desktop. With GNOME, the user is in control of everything, as the desktop is simple and easy to use, helping you get things done quickly. It is finely crafted and gives you easy access to all of your data.

The default desktop environment of numerous Linux distributions

It is the default desktop environment of many well known Linux distributions, such as Fedora, Red Hat, Debian GNU/Linux, Ubuntu GNOME, as well as some BSD flavors, such as GhostBSD.

Default applications

Default applications include the Baobab disk usage analyzer, Brasero CD/DVD burning software, Cheese webcam utility, Empathy instant messenger, Devhelp documentation browser, Anjuta IDE, Evince document viewer, Eye of GNOME image viewer, File Roller archive manager, Evolution mail, contacts, and calendar suite, Totem media player, Seahorse PGP and SSH key-manager, Orca screen-reader, Vinagre VNC client, Gedit text editor, and Nautilus file manager.

In addition, the following GNOME apps are available: Gcalctool, Glade, Boxes, Color Manager, Contacts, Control Center, Dictionary Dictionary, Disks, Documents, Font Viewer, Keyring Manager, Screenshot, Sound Recorder, Logs, System Monitor, Terminal, Gucharmap, and an impressive collection of games.

Bottom line

Many recent desktop environments were inspired by GNOME, including Cinnamon and MATE. But the truth is that this is one of the best desktop environments for Linux-based operating systems. It is our preferred desktop environment.

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There is a lot of activity and investment in the U.S supercomputer space now. After years of falling behind China for supercomputer superiority, the U.S is now storming back.

On Oct. 26, the Department of Energy’s National Nuclear Security Administration (NNSA) Lawrence Livermore National Laboratory (LLNL) formally dedicated the Sierra system, which is now the world’s third fastest supercomputer. The Sierra system is built with the same basic design as the IBM Summit system, which became the world’s most powerful supercomputer in June. Summit is a 200 petaflop system, while the newly dedicated Sierra currently tops out at 125 petaflops.

Sierra is a massive system spread out across 7,000 square feet of data center space. The system has 240 computing racks and 4,320 nodes.

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If you’re an engineer then you must be familiar with the term

“CAD”

. Computer Aided Design is a term which is used to define the use of computer technology aimed at designing real or virtual objects. It is an essential part of many streams of engineering and often refers to the drafting of a product or a part. Whether it is architecture, space shuttle research, auto parts design, bridge construction even jewelry or clothing, CAD plays an important role. It may help you design curves and figures in two-dimension and in three-dimensions as well. The CAD world in Windows has already some of the most powerful AutoCAD software. Unfortunately, Lunix didn’t have its fair share of such software.

Whilst it is possible to run CAD software on Linux through an emulator like Wine, this article will specifically point out the top CAD software available for Linux. So let’s dive in!

The FreeCAD is an open source, free software and the best option for 3D solid and general purpose design. The software makes comprehensive use of open source libraries like OpenCascade, Qt, Python, and Coin3D. You can use FreeCAD on Mac OS X+, Linux and Windows. FreeCAD is favored by many users for small tasks. However, it cannot be deployed on large scale because it is still running on version 0.17. The good news is that the development has recently picked up the pace.

One of the few shortcomings of FreeCAD is that it is not suitable for organic shape animations and 2D drawings. However, you can easily benefit from its mechanical engineering designing abilities. You can find FreeCAD version 0.15 from Ubuntu repositories. Following are the commands that can help you install it.

The current version is 0.17. The software offers newer builds on daily basis which can be obtained by performing following commands:

• Press (ctrl+alt+t) to open the terminal
• Once terminal is open, enter and run the following commands:

sudo add-apt-repository ppa:freecad-maintainers/freecad-daily
sudo apt update
sudo apt install freecad-daily

2. OpenSCAD

OpenSCAD is a free 3D CAD Software that is light weighed and flexible. It is one of the most complicated tools since it is limited interactivity. It requires you to ‘program’ the model and then it renders a visual model corresponding to your code. If you think of it, it works like a compiler, taking commands from you, interpreting them and providing you the results. You cannot actually draw the model in this software, you can only describe it. It is however complicated to use but once you get hold of it, you’ll really love using it.

Install OpenSCAD on your system by performing these commands:

sudo apt-get install openscad

3. BRL-CAD

BRL-CAD is a complete package with powerful Constructive Solid Geometry (CSG). It is one of the oldest CAD tools with over 20 years of development and production us by U.S military and is still being developed actively. It comes with interactive 3D solid geometry editor, image and signal processing tools, a network-distributed symmetric, multiprocessing and high-performance ray-tracer, a network-distributed frame buffer support, animation capabilities, ray-tracing and numerical processing libraries and much more. Now it is not AutoCAD but is still used widely for transport studies such as ballistic penetration. This software finds numerous other uses in tasks like system benchmarking, medical visualization of objects, planning of radiation doses, education and training of computer graphics. You might keep all this in mind before installing it.

4. QCad

QCad is an application designed specifically for 2D computer-aided drafting with an intuitive user interface. If you are looking for software which can help you in designing your home interior, this software is best. It features technical drawings and diagrams related to building plans and mechanical parts as well. It is available in two editions: the commercial one and the free one called Community Edition. The difference between the two editions is mostly regarding the number of features they have to offer and the date of availability. It uses DXF and DWG as its standard input and output format, 35 CAD fonts, part library with over 4800 CAD parts, multi-document interface and object snaps.

5. LibreCAD

The two highlighting properties of LibreCAD are that it is open source software which allows 2D Computer Aided designing. CAD is usually a resource-intensive task which requires a rather modest hardware. The free LibreCAD tool is lightweight and does not put much strain on resource usage. This makes it a good choice for CAD. As a 2D tool, we cannot expect it to render 3D models and renderings. You get the backup of an autosave option if you ever have struggle with large files whilst using this software. Libre CAD wins the contest for being the best software for creating geometric sketches.

LibreCAD can be installed on Linux by running the following command

sudo apt install librecad

Conclusion

All the tools mentioned above are currently under constant development and we can expect great things for them in the future. What kind of software you should go with certainly depends on what you’re looking for. Although, Linux is now catching up with Windows, in our opinion you should stick with what your college prescribes (if you’re a student) which will most probably run on Windows only. Speaking of industry standards and advanced requirements, these software might fail to meet professional expectations. But we highly respect the work that is being put forward by the developers of the above-mentioned software.

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Now a days most of the firms are trying to migrate their IT infrastructure and Telco Infra into private cloud i.e OpenStack. If you planning to give interviews on Openstack admin profile, then below list of interview questions might help you to crack the interview.

Q:1 Define OpenStack and its key components?

Ans: It is a bundle of opensource software, which all in combine forms a provide cloud software known as OpenStack.OpenStack is known as Stack of Open source Software or Projects.

Following are the key components of OpenStack

• Nova – It handles the Virtual machines at compute level and performs other computing task at compute or hypervisor level.
• Neutron – It provides the networking functionality to VMs, Compute and Controller Nodes.
• Keystone – It provides the identity service for all cloud users and openstack services. In other words, we can say Keystone a method to provide access to cloud users and services.
• Horizon – It provides a GUI (Graphical User Interface), using the GUI Admin can all day to day operations task at ease.
• Cinder – It provides the block storage functionality, generally in OpenStack Cinder is integrated with Chef and ScaleIO to service block storage to Compute & Controller nodes.
• Swift – It provides the object storage functionality. Generally, Glance images are on object storage. External storage like ScaleIO can work as Object storage too and can easily be integrated with Glance Service.
• Glance – It provides Cloud image services, using glance admin used to upload and download cloud images.
• Heat – It provides an orchestration service or functionality. Using Heat admin can easily VMs as stack and based on requirements VMs in the stack can be scale-in and Scale-out
• Ceilometer – It provides the telemetry and billing services.

Q:2 What are services generally run on a controller node?

Ans: Following services run on a controller node:

• Identity Service ( KeyStone)
• Image Service ( Glance)
• Nova Services like Nova API, Nova Scheduler & Nova DB
• Block & Object Service
• Ceilometer Service
• MariaDB / MySQL and RabbitMQ Service
• Management services of Networking (Neutron) and Networking agents
• Orchestration Service (Heat)

Q:3 What are the services generally run on a Compute Node?

Ans: Following services run on a compute node,

• Nova-Compute
• Networking Services like OVS

Q:4 What is the default location of VMs on the Compute Nodes?

Ans: VMs in the Compute node are stored at “/var/lib/nova/instances”

Q:5 What is default location of glance images?

Ans: As the Glance service runs on a controller node, all the glance images are store under the folder “/var/lib/glance/images” on a controller node.

Read More : How to Create and Delete Virtual Machine(VM) from Command line in OpenStack

Q:6 Tell me the command how to spin a VM from Command Line?

Ans: We can easily spin a new VM using the following openstack command,

# openstack server create –flavor –image –nic net-id= –security-group –key-name <VM_Name>

Q:7 How to list the network namespace of a tenant in OpenStack?

Ans: Network namespace of a tenant can be listed using “ip net ns” command

~# ip netns list
qdhcp-a51635b1-d023-419a-93b5-39de47755d2d
haproxy
vrouter

Q:8 How to execute command inside network namespace in openstack?

Ans: Let’s assume we want to execute “ifconfig” command inside the network namespace “qdhcp-a51635b1-d023-419a-93b5-39de47755d2d”, then run the beneath command,

Syntax : ip netns exec <command>

~# ip netns exec qdhcp-a51635b1-d023-419a-93b5-39de47755d2d “ifconfig”

Q:9 How to upload and download a cloud image in Glance from command line?

Ans: A Cloud image can be uploaded in glance from command using beneath openstack command,

~# openstack image create –disk-format qcow2 –container-format bare –public –file .qcow2 <Cloud-Image-Name>

Use below openstack command to download a cloud image from command line,

~# glance image-download –file <Cloud-Image-Name> –progress <Image-ID>

Q:10 How to reset error state of a VM into active in OpenStack env?

Ans: There are some scenarios where some VMs went to error state and this error state can be changed into active state using below commands,

~# nova reset-state –active

Q:11 How to get list of available Floating IPs from command line?

Ans: Available floating ips can be listed using the below command,

~]# openstack ip floating list | grep None | head -10

Q:12 How to provision a virtual machine in specific availability zone and compute Host?

Ans: Let’s assume we want to provision a VM on the availability zone NonProduction in compute-02, use the beneath command to accomplish this,

~]# openstack server create –flavor m1.tiny –image cirros –nic net-id=e0be93b8-728b-4d4d-a272-7d672b2560a6 –security-group NonProd_SG –key-name linuxtec –availability-zone NonProduction:compute-02 nonprod_testvm

Q:13 How to get list of VMs which are provisioned on a specific Compute node?

Ans: Let’s assume we want to list the vms which are provisioned on compute-0-19, use below

Syntax: openstack server list –all-projects –long -c Name -c Host | grep -i

~# openstack server list –all-projects –long -c Name -c Host | grep -i compute-0-19

Q:14 How to view the console log of an openstack instance from command line?

Ans: Console logs of an instance can be viewed from the command line using the following commands,

First get the ID of an instance and then use the below command,

~# openstack console log show

Q:15 How to get console URL of an openstack instance?

Ans: Console URL of an instance can be retrieved from command line using the below openstack command,

~# openstack console url show

Q:16 How to create a bootable cinder / block storage volume from command line?

Ans: To Create a bootable cinder or block storage volume (assume 8 GB) , refer the below steps:

• Get Image list using below

~# openstack image list | grep -i cirros
| 89254d46-a54b-4bc8-8e4d-658287c7ee92 | cirros | active |

• Create bootable volume of size 8 GB using cirros image

~# cinder create –image-id 89254d46-a54b-4bc8-8e4d-658287c7ee92 –display-name cirros-bootable-vol 8

Q:17 How to list all projects or tenants that has been created in your opentstack?

Ans: Projects or tenants list can be retrieved from the command using the below openstack command,

~# openstack project list –long

Q:18 How to list the endpoints of openstack services?

Ans: Openstack service endpoints are classified into three categories,

• Public Endpoint
• Internal Endpoint
• Admin Endpoint

Use below openstack command to view endpoints of each openstack service,

~# openstack catalog list

To list the endpoint of a specific service like keystone use below,

~# openstack catalog show keystone

Read More : Step by Step Instance Creation Flow in OpenStack

Q:19 In which order we should restart nova services on a controller node?

Ans: Following order should be followed to restart the nova services on openstack controller node,

• service nova-api restart
• service nova-cert restart
• service nova-conductor restart
• service nova-consoleauth restart
• service nova-scheduler restart

Q:20 Let’s assume DPDK ports are configured on compute node for data traffic, now how you will check the status of dpdk ports?

Ans: As DPDK ports are configured via openvSwitch (OVS), use below commands to check the status,

[email protected]:~# ovs-appctl bond/show | grep dpdk
active slave mac: 90:38:09:ac:7a:99(dpdk0)
slave dpdk0: enabled
slave dpdk1: enabled
[email protected]:~#
[email protected]:~# dpdk-devbind.py –status

Q:21 How to add new rules to the existing SG(Security Group) from command line in openstack?

Ans: New rules to the existing SG in openstack can be added using the neutron command,

~# neutron security-group-rule-create –protocol <tcp or udp> –port-range-min <port-number> –port-range-max <port-number> –direction <ingress or egress> –remote-ip-prefix <IP-address-or-range> Security-Group-Name

Q:22 How to view the OVS bridges configured on Controller and Compute Nodes?

Ans: OVS bridges on Controller and Compute nodes can be viewed using below command,

~]# ovs-vsctl show

Q:23 What is the role of Integration Bridge(br-int) on the Compute Node ?

Ans: The integration bridge (br-int) performs VLAN tagging and untagging for the traffic coming from and to the instance running on the compute node.

Packets leaving the n/w interface of an instance goes through the linux bridge (qbr) using the virtual interface qvo. The interface qvb is connected to the Linux Bridge & interface qvo is connected to integration bridge (br-int). The qvo port on integration bridge has an internal VLAN tag that gets appended to packet header when a packet reaches to the integration bridge.

Q:24 What is the role of Tunnel Bridge (br-tun) on the compute node?

Ans: The tunnel bridge (br-tun) translates the VLAN tagged traffic from integration bridge to the tunnel ids using OpenFlow rules.

br-tun (tunnel bridge) allows the communication between the instances on different networks. Tunneling helps to encapsulate the traffic travelling over insecure networks, br-tun supports two overlay networks i.e GRE and VXLAN

Q:25 What is the role of external OVS bridge (br-ex)?

Ans: As the name suggests, this bridge forwards the traffic coming to and from the network to allow external access to instances. br-ex connects to the physical interface like eth2, so that floating IP traffic for tenants networks is received from the physical network and routed to the tenant network ports.

Q:26 What is function of OpenFlow rules in OpenStack Networking?

Ans: OpenFlow rules is a mechanism that define how a packet will reach to destination starting from its source. OpenFlow rules resides in flow tables. The flow tables are part of OpenFlow switch.

When a packet arrives to a switch, it is processed by the first flow table, if it doesn’t match any flow entries in the table then packet is dropped or forwarded to another table.

Q:27 How to display the information about a OpenFlow switch (like ports, no. of tables, no of buffer)?

Ans: Let’s assume we want to display the information about OpenFlow switch (br-int), run the following command,

[[email protected] ~]# ovs-ofctl show br-int
OFPT_FEATURES_REPLY (xid=0x2): dpid:0000fe981785c443
n_tables:254, n_buffers:256
capabilities: FLOW_STATS TABLE_STATS PORT_STATS QUEUE_STATS ARP_MATCH_IP
actions: output enqueue set_vlan_vid set_vlan_pcp strip_vlan mod_dl_src mod_dl_dst mod_nw_src mod_nw_dst mod_nw_tos mod_tp_src mod_tp_dst
1(patch-tun): addr:3a:c6:4f:bd:3e:3b
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
2(qvob35d2d65-f3): addr:b2:83:c4:0b:42:3a
config: 0
state: 0
current: 10GB-FD COPPER
speed: 10000 Mbps now, 0 Mbps max
………………………………………

Q:28 How to display the entries for all the flows in a switch?

Ans: Flows entries of a switch can be displayed using the command ‘ovs-ofctl dump-flows‘

Let’s assume we want to display flow entries of OVS integration bridge (br-int),

[[email protected] ~]# ovs-ofctl dump-flows br-int

Q:29 What are Neutron Agents and how to list all neutron agents?

Ans: OpenStack neutron server acts as the centralized controller, the actual network configurations are executed either on compute and network nodes. Neutron agents are software entities that carry out configuration changes on compute or network nodes. Neutron agents communicate with the main neutron service via Neuron API and message queue.

Neutron agents can be listed using the following command,

~# openstack network agent list -c ‘Agent type’ -c Host -c Alive -c State

Q:30 What is CPU pinning?

Ans: CPU pinning refers to reserving the physical cores for specific virtual machine. It is also known as CPU isolation or processor affinity. The configuration is in two parts:

• it ensures that virtual machine can only run on dedicated cores
• it also ensures that common host processes don’t run on those cores

In other words we can say pinning is one to one mapping of a physical core to a guest vCPU.

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