Writing Multiple Plays A playbook is a YAML file containing a list of one or more plays. Remember that a single play is an ordered list of tasks to execute against hosts selected from the inventory. Therefore, if a playbook contains multiple plays, each play may apply its tasks to a separate set of hosts. This can be very useful when orchestrating a complex deployment which may involve different tasks on different hosts. You can write a playbook that runs one play against one set of hosts, and … [Read more...] about How to write multiple plays and per-play privilege escalation in Ansible
How to Write Ansible Playbook and run it using the ansible-playbook command
Ansible Playbooks and Ad Hoc Commands Ad hoc commands can run a single, simple task against a set of targeted hosts as a one-time command. The real power of Ansible, however, is in learning how to use playbooks to run multiple, complex tasks against a set of targeted hosts in an easily repeatable manner. A play is an ordered set of tasks run against hosts selected from your inventory. A playbook is a text file containing a list of one or more plays to run in a specific order. Plays allow you … [Read more...] about How to Write Ansible Playbook and run it using the ansible-playbook command
How to Run Ad-Hoc Commands Using Ansible
In this post, we will learn how to run a single Ansible automation task using an ad hoc command and explain some use cases for ad hoc commands. Running ad hoc Commands with Ansible An ad hoc command is a way of executing a single Ansible task quickly, one that you do not need to save to run again later. They are simple, online operations that can be run without writing a playbook. Ad hoc commands are useful for quick tests and changes. For example, you can use an ad hoc command to make sure … [Read more...] about How to Run Ad-Hoc Commands Using Ansible
Beginners Guide to Managing Package Module Streams in CentOS/RHEL 8
Introduction to Application Streams CentOS/RHEL 8.0 introduces the concept of Application Streams. Multiple versions of user-space components shipped with the distribution are now delivered at the same time. They may be updated more frequently than the core operating system packages. This provides you with greater flexibility to customize Red Hat Enterprise Linux without impacting the underlying stability of the platform or specific deployments. Traditionally, managing alternate versions of an … [Read more...] about Beginners Guide to Managing Package Module Streams in CentOS/RHEL 8
Common Error Messages from Command xfs_repair in Linux
The post explains some of the common error messages from command xfs_repair and the repairs that it performs. disconnected inode 242002, moving to lost+found xfs_repair found an inode that is in use but is not connected to the filesystem. The inode is moved to the filesystem's lost+found directory. Its name is its inode number (in this example, 242002). If the disconnected inode is a directory, the directory's subtree is preserved--all of its child inodes are automatically moved with it. So, … [Read more...] about Common Error Messages from Command xfs_repair in Linux
How to Permanently set the ethtool settings in CentOS/RHEL 6
Modifications made with the ethtool command are by default disappeared after a reboot. For permanent settings, the interface configuration file has to be edited. For each network device, there will be a file in the /etc/sysconfig/network-scripts/ For example, for device eth0 there will be /etc/sysconfig/network-scripts/ifcfg-eth0 containing the properties of the device. A line can be added to the file to automatically implement the settings allowed by the "ethtool -s" command. For example: # … [Read more...] about How to Permanently set the ethtool settings in CentOS/RHEL 6
How to Check if any of the RPM files were tempered with
Question: In some scenarios which it is suspected that the files in the system from an rpm installation, have been altered, changed, or tampered. For example, the system was hacked and a binary file of ssh tampered. How to check if changes were made on it comparing since installation? To verify and check if the files installed on a system with rpm or yum altered since installation using the following command: # rpm -V [PACKAGE_NAME] If you have any of the files altered in the rpm since … [Read more...] about How to Check if any of the RPM files were tempered with
How to Create a MySQL Docker Container for Testing
Docker is a container runtime environment that allows programs to operate in a jailed environment without any required external dependencies. Containers are similar in some concepts to virtual machines, however, they do not use a hypervisor and run in a single kernel instance, often sharing the instance with other containers. One of the prime features of containerization is the lack of external dependencies; the container has all of the runtime libraries and components needed to run the … [Read more...] about How to Create a MySQL Docker Container for Testing
Unable to run NGINX Docker due to “13: Permission denied”
The Problem The NGINX docker container was started using the below command: # docker run --detach --name nginx_server nginx 4ffbcd5ee796b8cce3f2c6ed4cce8927d2b13a040af07b36f7a866b2157290e8 But user failed to get connection to the NGINX server. Upon troubleshooting user found below error logs: # tail -f /var/log/audit/audit.log type=AVC msg=audit(1565283160.116:316): avc: denied { write } for pid=2387 comm="nginx" name="nginx" dev="dm-0" ino=140648937 … [Read more...] about Unable to run NGINX Docker due to “13: Permission denied”
How to extract RAR files in CentOS/RHEL 7 and 8
There is no default utility in CentOS/RHEL 7 systems to extract a .rar file. This post outlines the steps to install the unar package and use of unar command to extract files with .rar extension. 1. Log in as a root user (or use sudo) and configure the latest EPEL repositories to be able to install the unar package: # yum install epel-release Note: I recommend to disable all the existing repositories and just enable the EPEL repository if you do not want to face any conflict. 2, Now … [Read more...] about How to extract RAR files in CentOS/RHEL 7 and 8