Tuning Systems System administrators can optimize the performance of a system by adjusting various device settings based on a variety of use case workloads. The tuned daemon applies tuning adjustments both statically and dynamically, using tuning profiles that reflect particular workload requirements. Configuring Static Tuning The tuned daemon applies system settings when the service starts or upon the selection of a new tuning profile. Static tuning configures predefined kernel parameters … [Read more...] about Beginners Guide to Tuning Profiles in CentOS/RHEL
Archives for October 2020
How to use ansible-config to discover and investigate configuration options
Viewing Configuration Options If you want to find out what options are available in the configuration file, use the ansible-config list command. It will display an exhaustive list of the available configuration options and their default settings. This list may vary depending on the version of Ansible that you have installed and whether you have any additional Ansible plugins on your control node. Each option displayed by ansible-config list will have a number of key-value pairs associated … [Read more...] about How to use ansible-config to discover and investigate configuration options
How to write multiple plays and per-play privilege escalation in Ansible
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 tampered 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 with. For example, the system was hacked and a binary file of ssh tampered with. How to check if changes were made on it comparing since the 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 … [Read more...] about How to Check if any of the RPM files were tampered with