Search for a String in a File - Ansible module lineinfile
How to automate the search of a string “PasswordAuthentication no” in the “/etc/ssh/sshd_config” file using Ansible Playbook and lineinfile module.
How to Search for a String in a File with Ansible?
I’m going to show you some simple Ansible code. I’m Luca Berton and welcome to today’s episode of Ansible Pilot.
Ansible module lineinfile
ansible.builtin.lineinfile- insert/update/remove a single line of text in a file
Today we’re talking about the Ansible module lineinfile.
The full name is ansible.builtin.lineinfile, which means that is part of the collection of modules “builtin” with ansible and shipped with it.
It’s a module pretty stable and out for years and it supports a large variety of operating systems.
You are able to insert, update and remove a single line of text in a file.
Parameters
- path string - file path
- line string - text
- insertafter/insertbefore string - EOF/regular expression
- validate string - validation command
- create boolean - create if not exist
- state string - present/absent
- mode/owner/group - permission
- setype/seuser/selevel - SELinux
This module has some parameters to perform any tasks. The only required is “path”, where you specify the filesystem path of the file you’re going to edit. “line” is the line of text we would like to insert in the file, easy! By default, the text is going to be inserted at the end of the file, but we could personalize it in a specific position with insertafter/insertbefore. If there is any tool to validate the file we could specify in the validate parameter, very useful for configuration files. If the file does not exist we could also “create” it! Usually, we would like to insert a text line but we could also remove using state in conjunction with parameter absent. Let me also highlight that we could also specify some permissions or SELinux properties.
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demo
How to Search for a String in a File. How to search for a pattern in a file and return the result using only the Ansible built-in lineinfile module.
code
---
- name: search demo
hosts: all
vars:
myfile: "/etc/ssh/sshd_config"
myline: 'PasswordAuthentication no'
become: true
tasks:
- name: string found
ansible.builtin.lineinfile:
name: "{{ myfile }}"
line: "{{ myline }}"
state: present
check_mode: true
register: conf
failed_when: (conf is changed) or (conf is failed)
string present
- remote host
$ ssh [email protected]
[devops@demo ~]$ sudo su
[root@demo devops]# grep 'PasswordAuthentication no' /etc/ssh/sshd_config
PasswordAuthentication no
[root@demo devops]#
- Ansible execution
$ ansible-playbook -i virtualmachines/demo/inventory file_management/file_search.yml
PLAY [search demo] ********************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [string found] *******************************************************************************
ok: [demo.example.com]
PLAY RECAP ****************************************************************************************
demo.example.com : ok=2 changed=0 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
string different
- remote host
$ ssh [email protected]
[devops@demo ~]$ sudo su
[root@demo devops]# vim /etc/ssh/sshd_config
[root@demo devops]# grep 'PasswordAuthentication' /etc/ssh/sshd_config
PasswordAuthentication yes
[root@demo devops]#
- Ansible execution
$ ansible-playbook -i virtualmachines/demo/inventory file_management/file_search.yml
PLAY [search demo] ********************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [string found] *******************************************************************************
fatal: [demo.example.com]: FAILED! => {"backup": "", "changed": true, "failed_when_result": true, "msg": "line added"}
PLAY RECAP ****************************************************************************************
demo.example.com : ok=1 changed=0 unreachable=0 failed=1 skipped=0 rescued=0 ignored=0
file not present
- remote host
$ ssh [email protected]
[devops@demo ~]$ sudo su
[root@demo ssh]# ls -al /etc/ssh/sshd_config
ls: cannot access '/etc/ssh/sshd_config': No such file or directory
[root@demo ssh]#
- Ansible execution
$ ansible-playbook -i virtualmachines/demo/inventory file_management/file_search.yml
PLAY [search demo] ********************************************************************************
TASK [Gathering Facts] ****************************************************************************
ok: [demo.example.com]
TASK [string found] *******************************************************************************
fatal: [demo.example.com]: FAILED! => {"changed": false, "failed_when_result": true, "msg": "Destination /etc/ssh/sshd_config does not exist !", "rc": 257}
PLAY RECAP ****************************************************************************************
demo.example.com : ok=1 changed=0 unreachable=0 failed=1 skipped=0 rescued=0 ignored=0
Recap
Now you know how to Search for a String in a File with Ansible and how you could use successfully in your Playbook. Subscribe to the YouTube channel, Medium, Website, Twitter, and Substack to not miss the next episode of the Ansible Pilot.
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