Linux Book Center – Page 2 – Right choice to learn technology

About Puppet

Will see About puppet in this post. Puppet is a open source configuration management tool. Which will help us to reduce our working time by automating most of the day-to-day and other tasks in IT environment.

puppet is declarative one(Puppet domain specific language).
Puppet take care of all our regular repetitive task along with application deployment. configuration changes,etc.
Puppet written in Ruby.
Puppet is scale-label, which can be used any physical/virtual environments.
Codes written in puppet are idempotent by naturally.
It easily create/update and maintain the OS configuration files using its own declarative methods.

We can do below things using puppet on our OS without any human intervention.

* Installing application on various machines
* Managing Firewall ports
* Modifying configuration files
* Managing services, etc.

We have N number of Resources and Classes to build easily a complex environment over VMWare, Any Cloud environments.

How Puppet Works?

We have Master and agent concept in Puppet environment.
Master should be Installed and configured on Linux machines only and there is no support for Windows machine. But Agent can be Linux or Windows machines.
We have two deployment models
- Master-Agent deployment : Master and agent machines different machines. Master will manage the agent machines. Its used for Production environment
- Standalone deployment: Master and agent both packages are installed on one server and its used for Dev/Test Environment.
Puppet Master are Linux based machine where we need to install and configure “puppetserver” package and this will be responsible to create and maintain puppet codes to manage agent machines.
Agent machines are different servers in our environment which we would like to manage using puppet.
“Puppet-agent” package should be installed on agent machines
Agent machines will check with Master every “1800 Seconds(30 Mins)” to know if anything to be updated on agent machine.
If anything needs to be updated, Agent will pull from Master machine through puppet codes and this will be called us “pull mechanism” and will do required updates which is mentioned in puppet codes.
And we have “Push and Pull” based deployment.
In Push based, master will push the configuration updates to their agent machines
In Pull based model, Agents will establish connection with master and will pull the updates from master in periodic interval.

Workflow:

Administrator Login on Puppet Master to create/ Update puppet codes and this machine is responsible for puppet code management and contains different configurations in environment.
We have multiple agents in environment and puppet-agent package installed on agent machines.
Communication between master and agent will be established through secured certificates.
Puppet master will allow agent machines through port 8140
We make sure port 8140 enabled on firewall
Communication between master and agent has three steps
Once communication established, Agents send data to Master and the data includes, Host name, IP Address and MAC Address. These are called as facts.
Master uses this facts and compile a list with configuration which needs to be applied on agent and this will be called as catalog.
Catalog contains data such as packages to be installed/services, etc. which needs to be updated on agent machines based on puppet codes which wrote.
Agent uses the catalog to apply required changes on the nodes
Once agent received catalog, it will do required changes and nodes will report to master that will say the configuration has been applied ans successfully completed.
Puppet provides compatibility to get these reports using third party tools.

Reference: Puppet official Docs

Installing Docker on RHEL/ CentOS 8

Installing Docker on RHEL/ CentOS 8

Docker is a tool that uses kernel modules like namespace and cgroups to run container over single OS Instance.

It provides lightweight and efficient environment to deploy and manage applications by creating containers.

We are going to see Installing docker on RHEL/ CentOS 8 in this post

Installing Docker on RHEL/ CentOS 8

Docker available in below two types:

Docker EE(Enterprise Edition)
Docker CE(Community Edition)

Pre-Requisites:

Uninstall the old version of Docker using below command

yum  -y remove  docker-common docker container-selinux docker-selinux docker-engine

Your existing containers will be remain under /var/lib/docker

Installing dependent packages:

# yum -y install lvm2 device-mapper device-mapper-persis                                                                                        tent-data device-mapper-event device-mapper-libs device-mapper-event-libs

Adding Docker Repository:

Docker Inc still didnt replease Docker for RHEL8/ CentOS 8. So, we can use alternate one which is used for RHEL7/ CentOS7

# curl https://download.docker.com/linux/centos/docker-ce.repo -o /etc/yum.repos.d/docker-ce.repo

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

                                 Dload  Upload   Total   Spent    Left  Speed

100  2424  100  2424    0     0  22238      0 --:--:-- --:--:-- --:--:-- 22238

Docker community edition requires container.io => 1.2.2.3. But, its not available for RHEL/ CentOS 8. So, we need to skip and proceed the the docker installation in our own RISK.

# yum install docker-ce
 Docker CE Stable - x86_64                                                                                                                16 kB/s |  21 kB     00:01
 Error:
  Problem: package docker-ce-3:19.03.5-3.el7.x86_64 requires containerd.io >= 1.2.2-3, but none of the providers can be installed 

cannot install the best candidate for the job
package containerd.io-1.2.10-3.2.el7.x86_64 is excluded
package containerd.io-1.2.2-3.3.el7.x86_64 is excluded
package containerd.io-1.2.2-3.el7.x86_64 is excluded
package containerd.io-1.2.4-3.1.el7.x86_64 is excluded
package containerd.io-1.2.5-3.1.el7.x86_64 is excluded
package containerd.io-1.2.6-3.3.el7.x86_64 is excluded
 (try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)

Installing docker by skipping unavailable packages

[root@ip-172-31-44-32 ~]# yum -y install docker-ce --nobest

Output:

Installed:
   docker-ce-3:18.09.1-3.el7.x86_64                                                containerd.io-1.2.0-3.el7.x86_64       docker-ce-cli-1:19.03.5-3.el7.x86_64
   container-selinux-2:2.94-1.git1e99f1d.module+el8.0.0+4017+bbba319f.noarch       libnftnl-1.1.1-4.el8.x86_64            libcgroup-0.41-19.el8.x86_64
   policycoreutils-python-utils-2.8-16.1.el8.noarch                                libnfnetlink-1.0.1-13.el8.x86_64       libnetfilter_conntrack-1.0.6-5.el8.x86_64
   iptables-1.8.2-9.el8_0.1.x86_64

 
Skipped:
   docker-ce-3:19.03.5-3.el7.x86_64 

 
Complete!

Now Docker Version “3:18.09.1-3.el7.x86_64” has been installed.S

Start and enable the Docker service by using below command

# systemctl start docker
 
# systemctl enable docker
 Created symlink /etc/systemd/system/multi-user.target.wants/docker.service â /usr/lib/systemd/system/docker.service.

Check the docker service status

# systemctl status docker
 â docker.service - Docker Application Container Engine
    Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor preset: disabled)
    Active: active (running) since Fri 2020-01-17 05:37:17 UTC; 2min 4s ago
      Docs: https://docs.docker.com
  Main PID: 15635 (dockerd)
     Tasks: 18
    Memory: 53.5M
    CGroup: /system.slice/docker.service
            ââ15635 /usr/bin/dockerd -H fd://
            ââ15649 containerd --config /var/run/docker/containerd/containerd.toml --log-level info 
Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.341886251Z" level=info msg="Graph migration to content-addressabil>
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.342289173Z" level=warning msg="Your kernel does not support cgroup>
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.342309354Z" level=warning msg="Your kernel does not support cgroup>
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.342708097Z" level=info msg="Loading containers: start."
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.556082824Z" level=info msg="Default bridge (docker0) is assigned w>
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.654816733Z" level=info msg="Loading containers: done."
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.681089736Z" level=info msg="Docker daemon" commit=4c52b90 graphdri>
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.681241065Z" level=info msg="Daemon has completed initialization"
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal dockerd[15635]: time="2020-01-17T05:37:17.717122644Z" level=info msg="API listen on /var/run/docker.sock"
 Jan 17 05:37:17 ip-172-31-44-32.us-east-2.compute.internal systemd[1]: Started Docker Application Container Engine.

Now check the Docker installation by running a container using anyone the base image

# docker run -it hello-world
 Unable to find image 'hello-world:latest' locally
 latest: Pulling from library/hello-world
 1b930d010525: Pull complete
 Digest: sha256:9572f7cdcee8591948c2963463447a53466950b3fc15a247fcad1917ca215a2f
 Status: Downloaded newer image for hello-world:latest 

 Hello from Docker!
 This message shows that your installation appears to be working correctly.
 
To generate this message, Docker took the following steps:  
The Docker client contacted the Docker daemon.
The Docker daemon pulled the "hello-world" image from the Docker Hub.
 (amd64)
The Docker daemon created a new container from that image which runs the
 executable that produces the output you are currently reading.
The Docker daemon streamed that output to the Docker client, which sent it
 to your terminal. 
 
To try something more ambitious, you can run an Ubuntu container with:
  $ docker run -it ubuntu bash 
 
Share images, automate workflows, and more with a free Docker ID:
  https://hub.docker.com/ 

For more examples and ideas, visit:
  https://docs.docker.com/get-started/

Allowing non root users:

Check whether group called “Docker” availavle or not

# cat /etc/group | grep docker

docker:x:989:

Since group already exists, Now create a new user

# useradd abu

Check created users details like default UID, GID/ Groups added

# id abu
 uid=1001(abu) gid=1001(abu) groups=1001(abu)

Now add “abu” user to “Docker” group as another group.

# usermod -aG docker abu
 
# id abu
 uid=1001(abu) gid=1001(abu) groups=1001(abu),989(docker)

Now we can use this user to run docker instead if using root user.

Setup Docker Repository

Before installing the Docker Engine on your host, you need to setup the repository first. So, will see How to setup Docker Repository in this post.
After that, you can Install/Update the Docker from the repository.

Setup Docker Repository:

Yum should be configured on your host. Please use this post to know How to configure yum repository
Than, Packages required: yum-utils, yum-config-manager and device-mapper-persistent-data, lvm2 are required for devicemapper
Storage driver.
use below command to to install above mentioned packages using yum

#yum install -y yum-utils device-mapper-persistent-data lvm2

Since the packages are already installed on my host, Update has been done

Updated:

  device-mapper-persistent-data.x86_64 0:0.8.5-1.el7                                               lvm2.x86_64 7:2.02.185-2.el7_7.2

Use the below command to setup Docker Repository

#yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

    Loaded plugins: fastestmirror

    adding repo from: https://download.docker.com/linux/centos/docker-ce.repo

    grabbing file https://download.docker.com/linux/centos/docker-ce.repo to /etc/yum.repos.d/docker-ce.repo

    repo saved to /etc/yum.repos.d/docker-ce.repo

And check whether the repository added or not by issuing below command

#yum repolist | grep Docker

    docker-ce-stable/x86_64     Docker CE Stable - x86_64                         63

Installing Docker Engine:

To confirm the successful completion of Repository setup, will try to install New version of Docker engine now using below command.

#yum install docker-ce docker-ce-cli containerd.io 
 
Installed:
   containerd.io.x86_64 0:1.2.10-3.2.el7                       docker-ce.x86_64 3:19.03.5-3.el7                       docker-ce-cli.x86_64 1:19.03.5-3.el7 
 
Dependency Installed:
   container-selinux.noarch 2:2.107-3.el7                                                     libseccomp.x86_64 0:2.3.1-3.el7

Now start the Docker Engine:

# systemctl start docker
 
# systemctl status docker
  ● docker.service - Docker Application Container Engine
    Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled)
    Active: active (running) since Thu 2020-01-02 02:14:11 EST; 8s ago
      Docs: https://docs.docker.com
   Main PID: 60692 (dockerd)
    Memory: 37.6M
    CGroup: /system.slice/docker.service
            └─60692 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock  
 
Jan 02 02:14:10 localhost dockerd[60692]: time="2020-01-02T02:14:10.667134175-05:00" level=info msg="ccResolverWrapper: sending update to cc: {[{unix:/…odule=grpc
   Jan 02 02:14:10 localhost dockerd[60692]: time="2020-01-02T02:14:10.667153441-05:00" level=info msg="ClientConn switching balancer to \"pick_first\"" module=grpc
   Jan 02 02:14:10 localhost dockerd[60692]: time="2020-01-02T02:14:10.695465002-05:00" level=info msg="Loading containers: start."
   Jan 02 02:14:10 localhost dockerd[60692]: time="2020-01-02T02:14:10.952900918-05:00" level=info msg="Default bridge (docker0) is assigned with an IP ad…P address"
   Jan 02 02:14:11 localhost dockerd[60692]: time="2020-01-02T02:14:11.018716067-05:00" level=info msg="Loading containers: done."
   Jan 02 02:14:11 localhost dockerd[60692]: time="2020-01-02T02:14:11.040693143-05:00" level=warning msg="Not using native diff for overlay2, this may ca…r=overlay2
   Jan 02 02:14:11 localhost dockerd[60692]: time="2020-01-02T02:14:11.041056334-05:00" level=info msg="Docker daemon" commit=633a0ea graphdriver(s)=overl…on=19.03.5
   Jan 02 02:14:11 localhost dockerd[60692]: time="2020-01-02T02:14:11.041178502-05:00" level=info msg="Daemon has completed initialization"
   Jan 02 02:14:11 localhost dockerd[60692]: time="2020-01-02T02:14:11.072808771-05:00" level=info msg="API listen on /var/run/docker.sock"
   Jan 02 02:14:11 localhost systemd[1]: Started Docker Application Container Engine.
   Hint: Some lines were ellipsized, use -l to show in full.

Now verify the Docker using below command

# docker run hello-world
     Unable to find image 'hello-world:latest' locally
     latest: Pulling from library/hello-world
     1b930d010525: Pull complete
     Digest: sha256:4fe721ccc2e8dc7362278a29dc660d833570ec2682f4e4194f4ee23e415e1064
     Status: Downloaded newer image for hello-world:latest

 
Hello from Docker!
     This message shows that your installation appears to be working correctly. 

 
To generate this message, Docker took the following steps:
      1. The Docker client contacted the Docker daemon.
      2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
         (amd64)
      3. The Docker daemon created a new container from that image which runs the
         executable that produces the output you are currently reading.
      4. The Docker daemon streamed that output to the Docker client, which sent it
         to your terminal. 

 
To try something more ambitious, you can run an Ubuntu container with:
      $ docker run -it ubuntu bash 

 
Share images, automate workflows, and more with a free Docker ID:
      https://hub.docker.com/ 


For more examples and ideas, visit:
      https://docs.docker.com/get-started/

Thanks for reading this post and going forward will talk about Docker Engine more…

Reference: Docker Docs

Configuring Infoblox/NIOS Grid Master

Will see Configuring Infoblox/NIOS Grid Master in this post and for this we must have NIOS Virtual appliance installed already.

We should do some initial level settings to configure Grid Master in Infoblox and the steps are below:

1. Login to VSphere Client and select Infoblox host.
2. Select console
3. Login using admin credentials and Once, logged in you get prompt like below. login with superuser credentials in console.
Username: admin
Password: XXXXXXXXX

Infoblox>

4. We must have a valid license before configuring Grid Master. For that, issue below command and login to the infoblox support portal to register your device with Serial Number. Command will list the current version installed and Serial number of the appliance.

 Infoblox> show version 
 Version : 8.1.8-365387   
 SN      : 42181Ax7Ex1F54CxC1AFEDDx9EBx5Ex4F 
 Hotfix  : N/A

5. Also you can use the temporary license which will allow you to use 60 days trail period. Use the below command to install temp license.

For NIOS Virtual appliance use 2 & 8

Note: You must install Grid & NIOS license to join a Grid

 Infoblox > set temp_license
 1.DNSone (DNS, DHCP)
 2.DNSone with Grid (DNS, DHCP, Grid)
 3.Network Services for Voice (DHCP, Grid)
 4.Add NIOS License
 5.Add DNS Server license
 6.Add DHCP Server license
 7.Add Grid license
 10.Add Microsoft management license
 11.Add Multi-Grid Management license
 12.Add Query Redirection license
 13.Add Response Policy Zones license
 14.Add FireEye license
 15.Add DNS Traffic Control license
 16.Add Cloud Network Automation license
 17.Add Security Ecosystem license
 18.Add Threat Analytics license
 19.Add Flex Grid Activation license 
 Select license (1-17) or q to quit: 2
 This action will generate a temporary 60-day DNSone with Grid license.
 Are you sure you want to do this? (y or n): y
 DNS license already exists - ignoring.
 DHCP license already exists - ignoring.
 Grid license already exists - ignoring.
 Temporary license is not installed.

  Infoblox > set temp_license
  
   1. DNSone (DNS, DHCP)
   2. DNSone with Grid (DNS, DHCP, Grid)
   3. Network Services for Voice (DHCP, Grid)
   4. Add NIOS License
   5. Add DNS Server license
   6. Add DHCP Server license
   7. Add Grid license
   8. Add Microsoft management license
   9. Add Multi-Grid Management license
  10. Add Query Redirection license
  11. Add Response Policy Zones license
  12. Add FireEye license
  13. Add DNS Traffic Control license
  14. Add Cloud Network Automation license
  15. Add Security Ecosystem license
  16. Add Threat Analytics license
  17. Add Flex Grid Activation license
  
 Select license (1-17) or q to quit: 4
  
   1. IB-V805
   2. IB-V815
   3. IB-V825
   4. IB-V1405
   5. IB-V1415
   6. IB-V1425
   7. IB-V2205
   8. IB-V2215
   9. IB-V2225
  10. IB-V5005
  
 Enter a number corresponding to a NIOS model (1 - 10) or q to quit: 8
  
 This action will generate a temporary 60-day NIOS (Model IB-V2215) license.
 Are you sure you want to do this? (y or n): y
 NIOS (Model IB-2225) license already exists - ignoring.
  
 Temporary license is not installed.
  
 Infoblox >

Already I have installed the license so now it’s not installing.

6. Use below command to set the network. While installing the NIOS Virtual appliance itself, it will request for the network details like IP Address, Gateway, Subnet Mast. If you provided already then skip this step.

Infoblox > set network

Configuring Infoblox/NIOS Grid Master:

Now open a browser and enter browse for the NIOS GUI by enter like https://192.168.1.10 (Change IP Address with you NIOS Server IP)
Login to the Grid GUI with admin credentials.

Username: admin
Password: XXXXXX

Review and accept the License by Clicking on “I Accept”.
On Grid Configuration wizard select Configure a Grid Master and click Next.
Provide the required Grid properties like Grid Name, Shared secret, Show password, Hostname
Select No for Is the Grid Master is an HA pair? If you are configuring single Grid master and select yes for an HA pair.
Then provide Network settings like Hostname, IP Address, Gateway, Subnet Mask, Port settings. While installing Appliance itself if you provided these details, then no need to provide now. Because it will take those details automatically.
For HA Pair provide below details additionally. And then click Next

Virtual Router ID: This is unique number which from 1 to 255.

Required Ports and Addresses: Provide informations about the virtual interfaces like Node 1 HA and Lan port, Node 2 HA and Lan port. The VIP and IP Address should be from the same subnet. Note: that you cannot change the port settings.

Enter new Password and clickNext.
Select Timezone and click Next.
If you are enabling NTP then, click Add icon and provide IP Address of the NTP server and If you are disabling NTP simply select disable NTP and provide time and date manually the click Next.
Last screen will display the settings whatever you provided to configure the Grid Master. To complete that click Finish.

Reference: Infoblox document

Upgrading NIOS Software

Will see Upgrading NIOS Software in this post.

Before upgrading do the pre-implementation things for safer side mentioned below.

Check the current version of Infoblox execute below command in web console

admin> show version

Check the license using below command in web console

admin> show license

Note: If the NIOS holding temp license, it’s not advisable to upgrade the Version. It will lead to lose the GUI

Now we must take the Infoblox appliance database backup. Here we are mentioning NIOS configuration and discovery files as database. If anything goes wrong, we can use this backup to restore it to previous stat of the NIOS.

Grid -> Grid Manager -> Backup -> Manual Backup
-> My Computer -> Backup

Download the upgrade binaries (Bin/ Bin2) file from Infoblox support portal and do remember the path where you saved the file

https://support.infoblox.com

Step 1:

Click on download tab and you will get next screen. From there select “NIOS Archives (.BIN/2 files)”

Step 2:

Once selected “NIOS Archives (.BIN/2 files)” from the dropdown list, next click on “Available for download” button

Step 3:

On next step you will get list of available download and from there click the appropriate version BIN or BIN2 file to download the upgrade. We can avoid “.DDI.OVA FILES” and “CHECKSUM FILES”, because it not required for the upgrade process.

Recommended to download the .BIN Files for the appropriate version.

Download and keep it in a host which in same network to upload in Grid Master GUI for upgrade and do remember the path.

Upgrading NIOS Software:

Upload the binaries to Infoblox Grid Master (Grid -> Upgrade -> Upload)
Once upload completed, Distribute button will be enabled. Then click on Distribute to distribute the uploaded binaries to remote nodes (Grid -> Upgrade -> Distribute)
Once distribution completed, Test button will be enabled. To verify the integrity of upgrade files click Test (Grid -> Upgrade -> Test)
Finally click on upgrade to apply the update (Grid -> Upgrade -> Upgrade)

Post Upgrade of NIOS please do the below checks:

1. Revert all nodes to the previous version (Grid -> Upgrade -> Revert -> Grid)

Grid Master will display warning message. Read the warning carefully and then click Yes to proceed further.

In absence of Grid Master GUI, we can restore the backup to set NIOS Configuration to the previous stat.

Reference: Infoblox document

How to install RHEL 8

We are going to learn how to install RHEL 8 Operating system in this post. It supports “Appliction Stream” which will allow developer tools and read our previous post to know more about RHEL 8 features.

Minimum System Requirements:

4 GB RAM
20 GB unallocated disk space
64-bit x86 or ARM System

and it will supports below architecture,

AMD or Intel x86 64-bit
64-bit ARM
IBM Power Systems, Little Endian & IBM Z

Keep the RHEL 8 Media or Image file ready to start the installation. Use the below link to download RHEL 8

https://access.redhat.com/downloads/

Boot the system using RHEL 8 media or image file and it will start the installation like below and by using “Tab” select “RedHat Enterprise Linux 8.0.0″and press “Enter” key in keyboard to start the installation.

On next screen, you will get a list that is asking you to select the System language and keyboard layout like below. Select your preferred language and click on continue

Then next you will get a screen which is the place to provide all information to install the operating system. Click on “Installation Destination” for partitioning.

In next screen, select “Automatic” for auto partitioning, which is done by Operating System itself. In this option i will take all the available disk for installation

Select “Custom” to do partitioning by yourself. Here you need to select the required mount points and size concern to that mounts. Default mount points will be /(root), swap, /boot. See the below screenshots of custom partitioning which i done in this installation.

Select the partition type “Standard Partition, LVM, LVM Thin Provisioning” which type you want to create partition. Here i selected LVM type for this installation. LVM is best option where you can extend or reduce the partition size whenever needed.

Select Filesystem(partition) and provide size of the filesystem like below

Finally i have created few of the filesystems using available disk space with LVM. Click on done from the top left side of the screen.

Next screen it will ask for the confirmation to make changes in disk. So, Click on “Accept Changes” to proceed further.

Next you can see a window where you can select the Language, Date and time, Time zone, network settings, Installation source, Installation Destination and Software selection.

Click on “software selection”

You will find a screen like below. From that you can select the option based on you Configuration, for what you are going to use this server. I used “Minimal Install”. Click on Done from the top left side corner of the screen and again click “Begin Installation”.

Now it will start the installation and the same time it will show you the option to set password for root user and if you want to create any other user, you can create and click “Done”

After the Installation click on “Reboot” from the bottom right side corner of the screen and finally system will boot up with new operating system installed and prompt for username and password.

Now your system is ready for production.

Thanks for reading this post.

Reference: RedHat Documentation

RedHat Enterprise Linux 8 (RHEL 8) released

RedHat Enterprise Linux 8 (RHEL 8) released on 7th May 2019 and another important thing is that this happened after acquisition of RedHat by IBM on 28th October 2018.

Release Date:

RHEL 8 released on 7th May 2019 and now its available for production environment.

RHEL 8 Download link:

Architecture:

AMD64, Intel 64-bit, 64-bit ARM, IBM Power Systems, and IBM Z

Overview:

RHEL 8 uses upstream Linux kernel 4.18

This is Secure, Stable and good foundation for hybrid cloud deployments.

New Features:

It Supports 4PB Physical memory

Wayland is default display server, instead of Xorg.

XFS supports shared copy-on-write data extends.

Now cockpit is default package and it comes along with RedHat OS image

RHEL 8 distributed with two main repositories: BaseOS & AppStream

RHEL 8 comes with new version of yum which is based on DNF.

nftables replaces iptables in network framework and we can convert existing iptables rules to nftables format for use.

Nginx 1.14 available in default repository.

Now in RHEL 8 sosreport can report any load of eBPF (extended Berkeley Packet Filtering) programs and maps

Geoliet2 database replaces geolite

In Cluster part we have new pcs commands to list and test available watchdog devices.

In the next post will see how to install RHEL 8

Reference: RedHat access portal

How to Register and Enable RedHat Subscriptions, Repositories for RHEL7

This post will guide you to know How to Register and Enable RedHat Subscriptions, Repositories for RHEL7 before system full upgrade or to install any packages from EPEL Repository in RedHat.

Enabling RedHat repositories are mandatory to install any packages using yum. RedHat subscription has the registered system details once the registration has been done.

Requierment:

All we need is newly installed system with RedHat 7.

Registering and Activating RedHat Subscrition:

As a first step we should go to the RedHat Customer portal and register there. After the successful registration do remember the credentials.

Now login to the RHEL7 server and use the below command to register your system to RedHat Customer portal with RedHat credentials which you created just before

#subscription-manager register --username <username> --password <password>

Once register your system, use the “list” option to get the all available subscription and than note down the subscription pool id which you need to activate it.

#subscription-manager list -available

if your not getting any list, than your system registration with RedHat customer portal is not purchased for subscription. Please get in touch with RedHat to proceed further.

Once you got the list of available subscription, you can use the below command to activate the subscription

#subscription-manager subscribe --pool=Pool ID number

To know the status of consumed subscription use the below command

#subscription-manager list –consumed

To list the available subscription use the below command

#subscription-manager list

Once your system registered with RedHat customer portal and activated subscription, you can enable the repositories . Use the below command to list the repositories for you subscription.

#subscription-manager repos --list

use the below command to list the available repository

#yum repolist all

To enable a specific repository, open “vi /etc/yum.repos.d/redhat.repo” file and ensure that “enbaled=1” for concern repository which you want to enable

Now list only enabled repository by executing below command

#yum repolist

Now you can use required yum commands to update your system/ install any packages like below

#yum update
#yum install <package_name>

Reference: RedHat portal

How to install Nagios Core server 4.4.3 on RHEL 6/7 & CentOS 6/7

This post will help you to know How to install Nagios Core server 4.4.3 on RHEL 6/7 & CentOS 6/7.

Nagios is a powerful monitoring tool. It will help to monitor a infrastructure.

It will monitor applications, service and entire infrastructure.

Required Packages:

httpd
php
php-cli
gcc
unzip
wget
glibc
glibc-common
gd
gd-devel
net-snmp

[root@nagiosrv ~]yum install httpd php php-cli gcc unzip wget glibc glibc-common gd gd-devel net-snmp

As we have installed httpd and this will be useful when we access the Nagios core to manage through web console.

 [root@nagiosrv yumrepo]# systemctl start httpd

Now create Nagios user account using below command:

[root@nagiosrv yumrepo]# useradd Nagios
[root@nagiosrv yumrepo]# passwd nagios
Changing password for user nagios. 
New password: 
BAD PASSWORD: The password contains the user name in some form 
Retype new password: 
passwd: all authentication tokens updated successfully.

Now we need to create a group “nagcmd” to setup Nagios and then add the users “nagios” & “apache” to be a part of group: nagcmd

[root@nagiosrv yumrepo]# groupadd nagcmd
[root@nagiosrv yumrepo]# usermod -a -G nagcmd nagios 
[root@nagiosrv yumrepo]# usermod -a -G nagcmd apache

Ñow its time to start Nagios Core server installation

Since Nagios third party tool, we need to download first for installation using below commands:

[root@nagiosrv ~]# cd /opt
[root@nagiosrv opt]# wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.3.tar.gz 
[root@nagiosrv opt]# tar -xvf nagios-4.4.3.tar.gz 
[root@nagiosrv nagios-4.4.3]# ./configure --with-command-group=nagcmd 
[root@nagiosrv nagios-4.4.3]# make all 
[root@nagiosrv nagios-4.4.3]# make install
[root@nagiosrv nagios-4.4.3]# make install-init
[root@nagiosrv nagios-4.4.3]# make install-daemoninit
[root@nagiosrv nagios-4.4.3]# make install-commandmode
[root@nagiosrv nagios-4.4.3]# make install-config
[root@nagiosrv nagios-4.4.3]# make install-exfoliation

Now configure Apache for Nagios installation using below command:

[root@nagiosrv nagios-4.4.3]# make install-webconf

Will configure Apache authentication for nagiosadmin which is default user. Don’t change this username. If you are changing then need to do more changes in configuration file.

[root@nagiosrv nagios-4.4.3]# htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Now restart the apache

[root@nagiosrv nagios-4.4.3]# systemctl restart httpd

As a next step need to install Nagios plugins, once installed Nagios core using below commands:

[root@nagiosrv nagios-4.4.3]# cd /opt
[root@nagiosrv opt]# wget http://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
[root@nagiosrv opt]# tar -xvf nagios-plugins-2.2.1.tar.gz
[root@nagiosrv opt]# cd nagios-plugins-2.2.1

Now install and compile the plugins using below command:

[root@nagiosrv nagios-plugins-2.2.1]# ./configure --with-nagios-user=nagios --with-nagios-group=Nagios
[root@nagiosrv nagios-plugins-2.2.1]# make
[root@nagiosrv nagios-plugins-2.2.1]# make install

We installed Nagios core and plugins. So, now will check and verify the configuration using below command:

[root@nagiosrv nagios-plugins-2.2.1]#
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

The output should give 0 Errors and 0 Warnings. If you get the same, then will start the Nagios like below

[root@nagiosrv nagios-plugins-2.2.1]# systemctl start
nagios

Check SELinux mode using below command:

[root@nagiosrv ~]getenforce
Enforcing

If SELinux is in Enforcing mode, Than change it to Permissive mode or disable it like below

[root@nagiosrv ~]# setenforce 0

Now make sure to enable web server permanently in firewall using below command:

[root@nagiosrv ~]# firewall-cmd --permanent
--add-service=http

Execute below command to make affect in firewall changes which we did using our previous command

[root@nagiosrv ~]# firewall-cmd –reload

Finally we have done everything and now will check whether the web console working on not

Enter url like below in your web browser and replace the IP_ADDR with your server ip

http://IP_ADDR/nagios

It will ask for the username and password. Remember that we already created a user name “nagiosadmin”. We can use that to login the console.

How to install Nagios Core server 4.4.3 on RHEL 6/7 & CentOS 6/7

Enter the nagiosadmin credentials and the web console looks like below

From the left side pan click on “Hosts” and it will show list of hosts which is added for monitoring.
Since, we doesn’t added any host, it will show only localhost, which is Nagios server like below

Finally we installed and configured Nagios server. Thanks for readin

VMware:Events:warning: Event: com.vmware.vc.HA.NotAllHostAddrsPingable

We are going to see how to resolve VMware:Events:warning: Event: com.vmware.vc.HA.NotAllHostAddrsPingable or management host not responding in cluster issue in VMWare VCentre

Steps:

Login to VMWare webclient and check the status of the host
If the host is non responsive mode, try to ping host by using IP Address of the host.
If the ping request getting failed, then try to login to the IDrac for the host status
Try to login the host through virtual console
if the server is not responding , reboot the server and be informed to the concern team before rebooting or if its responding and asking for password, simply restart the ESXi and check the server status again vcenter.
same time check nslookup and hostname commands are giving appropriate output.

Above steps mostly will help to resolve this issue.