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
DevOps
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
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 Use user-defined Functions in awk
User-Defined Functions You can create user-defined functions in a awk script file using the func or function keywords. Placement in the file is not important; the function definition can occur anywhere in the awk script. The function can take arguments (local to the function only) or use any existing variable. The syntax of a function definition is: func function_name ([optional_arg] . . .) { statements } or function function_name ([optional_arg] . . .) { statements } The … [Read more...] about How to Use user-defined Functions in awk
Using Loops (while, for) in awk scripts
The awk programming language contains many of the programming concepts that are used in shell scripting. Conditionals, such as the if statement and loops, such as the following can also be used in awk programming. The while loop The do while loop The for loop The if Statement The if statement can have two branches: an if branch and an else branch. If the condition is true, the if branch is executed; if the condition is false, the else branch is executed. if (condition) { … [Read more...] about Using Loops (while, for) in awk scripts
Beginners Guide to Using “trap” to Catch Signals and Handle Errors in Shell Script
Shell Signal Values A signal is a message that some abnormal event has taken place or a message requesting another process do something. The signal is sent from one process to another process. Typically, a process sends a signal to one of its own subprocesses. You can obtain more information on signals from the signal and kill man pages. You use the kill command to send signals to processes. The root user can send any signal to any process. Other users can only send signals to processes they … [Read more...] about Beginners Guide to Using “trap” to Catch Signals and Handle Errors in Shell Script
How to Make a Variable read-only (constant) in Bash and Korn Shell
Creating Bourne Shell Constants A variable can be made read-only with the following syntax: readonly var[=value] The square brackets around =value mean that the assignment of a value is not always necessary. For instance, if the variable had previously been created and assigned a value, and you now want to make it read-only (and not change its current value), do not use =value. If the variable did not previously exist, and you make it read-only, you may never assign a value to the … [Read more...] about How to Make a Variable read-only (constant) in Bash and Korn Shell