linux 7 – Technology evangelist

Failed to start OpenStack Identity Service (code-named Keystone).

Posted on February 12, 2016December 16, 2016 by Vishwanath Mule

When you installed Openstack using packstack you might have faced openstack-keystone service issue. When try it to restart it fails with code-name keystone error.

I have done some research on it and found the solution.

The issue is with Openstack Keystone Service which we have configured using httpd deamon in answers.cfg file ( configuration file used to install Openstack using packstack)

Now openstack-keystone service will not start as http service is already in started mode and we haven’t created any relation between openstack-keystone and http service.

So to start openstack-keystone service we have to create symbolic link and point openstack-keystone service to http service.

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Linux, Uncategorized

Graphical/Desktop UI for Centos 7/RHEL 7

Posted on January 19, 2016December 16, 2016 by Vishwanath Mule

Many times we need graphical UI to open/run some applications. So following are simple and quick steps to create graphical UI on Centos7/RHEL7.

First check you have yum repository configured to access local or internet repository

#yum repolist

Graphical UI filesets will install in group so that all required/dependent filesets will install automatically. Check all available groups in yum repository using group list

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Linux, Openstack

Multinode Openstack Installation on Centos 7/RHEL 7

Posted on December 21, 2015December 16, 2016 by Vishwanath Mule

This post describing multinode OpenStack installation on centos7/rhel7 for Liberty release. If you want to do single node installation please refer my earlier post.

We are installing OpenStack onto 3 nodes controller,compute and network using packstack utility

Following is 3 node Openstack Architecture and related Openstack services running on respective nodes. I am using two network one is management network of 192.168.56.* which is used for internal communication between nodes and one external network used to assign public IP to VM and to access instances/VM from outside. I am also using NATed DHCP ip on each nodes to download required filesets from internet.

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Linux, Openstack

Openstack Liberty install using packstack on Centos 7/RHEL 7

Posted on November 30, 2015December 16, 2016 by Vishwanath Mule

This post is a quickstart guide to install OpenStack Liberty release using packstack on CentOS7.

This is very basic POC setup where all components will be installed on one node only. I will create another post for multinode installation setup.

Install CentOS using minimal install Software Selection.

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Linux, network

Network Configuration in RHEL 7/Centos 7

Posted on June 12, 2015December 16, 2016 by Vishwanath Mule

In this post I am going to show how to do network configuration in rhel7/centos7. We have ip command introduced in linux way back but we never used it. In this post we will use ip related commands which isnot easy to use as it has many options need to provide to get relevant output.

to see IP address details normally we used ifconfig command we check the same using ip addr show command.

Here we an see ipv4 address of eth0 interface along with ipv6 address and network UP status and mtu size.
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Linux, Security

Access Control List (ACL) Permissions in RHEL 7/Centos 7

Posted on June 11, 2015December 16, 2016 by Vishwanath Mule

Today I am going to show you how to use access control list (ACL) permissions in rhel7. Traditionally we have assigned permission to one user/owner and one group for file or directory but in some cases we need other user or other group apart from owner need to have readonly access or write access on same directory. To achieve this we have access control list permission concept in Linux.

Other users and and groups can also access file or directory even when they are not owners and member of group who is having ownership on that file or directory.

we use only two commands getfacl to see ACL permissions on directory/file and setfacl to set ACL permissions. We can even set default ACL so that new files and sub-directories created in directory will inherit ACL permissions of parent directory.

The filesystem needs to be mounted with ACL support enabled. XFS filesystems have built-in ACL support and Ext4 filesystem in RHEL7 have ACL option enabled by default. In earlier versions of RHEL you may need the ACL option included with mount request.

First we see ACL permission on file named prod.conf.

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Linux, Security

Configure SSH key based authentication on rhel 7/centos 7

Posted on May 31, 2015December 16, 2016 by Vishwanath Mule

In this post I am going to show you how to configure SSH key based authentication on rhel7/centos7. Configuration of SSH key based authentication is little different in rhel7 compared to traditional method of manually copying public key to another server. Users can login using ssh with password and authenticate using public key authentication.

On every server we have two keys private and public. Private key is used as authentication credentials like password which must be kept secret and secure. Public key we need to copy on the server where user want to login and used to verify private key so public key does not need to be secret.

How authentication happens in SSH key key based authentication. SSH server that has public key can issue a challenge that can only be answered by system who is holding private key as a result user can authenticate without password only with the help of public key and system grant login access to the user.

Use ssh-keygen command to generate private and public key as follows

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