Essential Operations: Ansible Tool

  1. Features:

  • Developed based on Python (paramiko), modular work

  • Communicates with remote hosts via SSH, no agent installation required on clients, only Ansible needs to be installed on the control node

  1. Management Architecture

  • Inventory host list: List of managed host IPs, categorized

  • Ad-hoc: Command line batch management (ans module) for temporary tasks

  • Playbook mode: Similar to writing a script with several operations (task collection), allowing this script to be run repeatedly

  1. Deployment

  • RHEL/Centos systems

# Install EPEL repository (Ansible is in the EPEL source)
sudo yum install -y epel-release
# Install Ansible
sudo yum install -y ansible

  • Ubuntu/Debian systems

# Update apt source
sudo apt update
# Install Ansible
sudo apt install -y ansible

  • Install via pip for any system

# Ensure pip is installed
sudo apt install -y python3-pip  # Ubuntu/Debian
# or
sudo yum install -y python3-pip  # RHEL/CentOS
# Install Ansible using pip
sudo pip3 install ansible

  • Verify installation, version information and configuration file path should appear

ansible --version

Offline Installation

Method 1: Pre-download RPM/DEB packages

# CentOS/RHEL
yum install --downloadonly --downloaddir=/tmp/ansible ansible
# Debian/Ubuntu
apt-get install --download-only ansible -y

Copy the /tmp/ansible directory to the internal network machine

Execute on the internal network

# CentOS/RHEL
yum localinstall -y /tmp/ansible/*.rpm
# Debian/Ubuntu
dpkg -i /tmp/ansible/*.deb
apt-get -f install -y

Method 2: Offline Python + pip packages

If you prefer to use pip

Execute on the external network machine:

pip download ansible-core==2.15.* -d /tmp/ansible-pkgs
pip download ansible==8.* -d /tmp/ansible-pkgs

Copy /tmp/ansible-pkgs to the internal network

Install on the internal network:

pip install --no-index --find-links=/tmp/ansible-pkgs ansible

Method 3: Directly package the virtual environment

Create venv on the external network:

python3 -m venv /opt/ansible-venv
source /opt/ansible-venv/bin/activate
pip install ansible

Package the entire <span>/opt/ansible-venv</span>, transfer to the internal network.

After unpacking on the internal network, use <span>bin/ansible</span>, <span>bin/ansible-playbook</span>.

Configuration File ansible.cfg

The pip installation does not include the default ansible.cfg configuration file.

# You can specify the default configuration file when using commands
ansible [command parameters] --config /path/to/your/ansible.cfg

  • The priority order for recognizing the default configuration file during ansible execution is as follows:

When you execute the <span>ansible --version</span> command, the current working directory is <span>/root/ansible/</span>.

The priority order for Ansible to find the configuration file (from high to low) is as follows:

  1. Path specified by the command line using the <span>--config</span> parameter (highest priority)

  2. Current working directory’s <span>./ansible.cfg</span> (i.e., the directory you are in)

  3. User home directory’s <span>~/.ansible.cfg</span>

  4. System-level configuration <span>/etc/ansible/ansible.cfg</span>

The configuration file can also specify the location of the host inventory.

  1. ans-inventory Host Inventory

Ansible defaults to reading the hosts file in /etc/ansible/hosts, and you can also place the inventory file in a specified directory, using the -i option when running ansible to specify the inventory file

# Password-based connection
[root@ansible ~]# vim /etc/ansible/hosts
# Method 1 Host+Port+Password
[webserver]
192.168.1.31 ansible_ssh_port=22 ansible_ssh_user=root ansible_ssh_pass="123456"
192.168.1.32 ansible_ssh_port=22 ansible_ssh_user=root ansible_ssh_pass="123456"
192.168.1.33 ansible_ssh_port=22 ansible_ssh_user=root ansible_ssh_pass="123456"
192.168.1.36 ansible_ssh_port=22 ansible_ssh_user=root ansible_ssh_pass="123456"
# Method 2 Host+Port+Password
[webserver]
192.168.1.3[1:3] ansible_ssh_user=root ansible_ssh_pass="123456"
# Method 2 Host+Port+Password
[webserver]
192.168.1.3[1:3]
[webserver:vars]ansible_ssh_pass="123456"

# Key-based connection
After distributing the key, you do not need to put the password in the file for passwordless use

# Method 1 Host+Port+Key
[webserver]
192.168.1.31:2219
192.168.1.32
192.168.1.33
192.168.1.36
# Method 1 Alias Host+Port+Key
[webserver]
node1 ansible_ssh_host=192.168.1.31 ansible_ssh_port=22
node2 ansible_ssh_host=192.168.1.32 ansible_ssh_port=22
node3 ansible_ssh_host=192.168.1.33 ansible_ssh_port=22
node6 ansible_ssh_host=192.168.1.36 ansible_ssh_port=22

# Usage of Host Groups

# Host Group Variable Name+Host+Password
[apache]
192.168.1.36
192.168.1.33
[apache.vars]ansible_ssh_pass='123456'
# Host Group Variable Name+Host+Key
[nginx]
192.168.1.3[1:2]
# Define multiple groups, treating one group as members of another group
[webserver:children]  # The webserver group includes two subgroups: apache nginx
apache
nginx

Temporarily Specify Inventory

  1. First edit a host definition inventory

[root@ansible ~]# vim /etc/dockers
[dockers]
192.168.1.31 ansible_ssh_pass='123456'
192.168.1.32
192.168.1.33

  1. Specify the <span>inventory</span> when executing the command

[root@ansible ~]# ansible dockers -m ping -i /etc/dockers -o 192.168.1.33 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}
192.168.1.32 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}
192.168.1.31 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}

Built-in Parameters of Inventory

  1. Ansible Ad-hoc

Ad-hoc —— Temporary, in <span>ansible</span> refers to commands that need to be executed quickly and do not need to be saved. Simply put, it is executing simple commands — a single command. For complex commands, it is referred to as <span>playbook</span>, similar to the <span>saltstack</span> state file.

Ansible Command Format

Common Parameters:

# Common two formats
ansible  -m shell  -a ""  -o
# inventory is the host list, the default configuration file is /etc/ansible/hosts, can execute in groups
-m followed by the module name, commonly used are shell, copy, etc.
-a followed by module parameters, for example, shell module followed by command, copy module followed by source path (src) and destination path (dest)
-C, --check  # Check syntax
-f FORKS # Concurrency
--list-hosts # List host list
-o Use concise output

# Example
ansible webserver -m shell -a 'uptime' -o
192.168.1.36 | CHANGED | rc=0 | (stdout)  13:46:14 up 1 day,  9:20,  4 users,  load average: 0.00, 0.00, 0.00
192.168.1.33 | CHANGED | rc=0 | (stdout)  21:26:33 up 1 day,  8:51,  3 users,  load average: 0.00, 0.01, 0.05
192.168.1.31 | CHANGED | rc=0 | (stdout)  21:26:33 up 1 day,  8:50,  3 users,  load average: 0.00, 0.01, 0.05
192.168.1.32 | CHANGED | rc=0 | (stdout)  21:26:33 up 1 day,  8:59,  3 users,  load average: 0.00, 0.01, 0.05

Command Explanation:

Host Group Matching:

# Group configuration information as follows: Here defines a nginx group and an apache group
[root@ansible ~]# ansible nginx --list  hosts (2):    192.168.1.31    192.168.1.32
[root@ansible ~]# ansible apache --list  hosts (3):    192.168.1.36    192.168.1.33    192.168.1.32
# Match all hosts in one group
[root@ansible ~]# ansible apache -m ping
# Match all hosts that are in apache group but not in nginx group
[root@ansible ~]# ansible 'apache:!nginx' -m ping -o
192.168.1.36 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}
192.168.1.33 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}
# Match machines that are in both apache and nginx groups (intersection)
[root@ansible ~]# ansible 'apache:&nginx' -m ping -o
192.168.1.32 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}
# Match all machines in both apache and nginx groups (union); equivalent to ansible apache,nginx -m ping
[root@ansible ~]# ansible 'apache:nginx' -m ping -o
192.168.1.32 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}
192.168.1.31 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}
192.168.1.33 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}
192.168.1.36 | SUCCESS => {"ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, "changed": false, "ping": "pong"}

  1. Common Ansible Modules

  • Command Module

Default module, not as flexible and powerful as shell, but safer

  • Shell

Similar to command, executes commands using shell

# Modify configuration file to make shell the default module
vim /etc/ansible/ansible.cfg
module_name = shell

  • Script Module

Runs scripts on remote hosts from the ansible server

Example:<span>ansible websrvs -m script -a /data/test.sh</span>

  • Copy Module

Copy: Copies files from the control node to remote hosts

src: Source file, specifies the local path of the file to be copied (if there is a /, it copies the contents of the directory, not the directory itself)

dest: Specifies the target path

mode: Sets permissions

backup: If the target machine’s file exists, back up the source file before replacing it.

content: Replaces src, specifies the content of the local file, generating the target host file

Example: ansible all -m copy -a “src=./test.yml dest=/root/qwer/ backup=yes”

# Corresponding yml file
- name: Copy file and enable backup
  copy:
    src: ./local_test.yml
    dest: /root/qwer/test.yml
    backup: yes  # Enable backup

ansible websrvs -m copy -a “src=/root/test1.sh dest=/tmp/test2.sh owner=wang mode=600 backup=yes” If the target exists, it will overwrite by default, here it specifies to back up first

ansible websrvs -m copy -a “content=’test content\nxxx’ dest=/tmp/test.txt” Specifies content, directly generates the target file

  • Fetch Module

Fetch: Extracts files from remote hosts to the control node, opposite of copy, currently does not support directories.

ansible websrvs -m fetch -a ‘src=/root/test.sh dest=/data/scripts’

Will generate a directory with different numbers for each managed host, preventing filename conflicts

ansible all -m shell -a ‘tar jxvf test.tar.gz /root/test.sh’

ansible all -m fetch -a ‘src=/root/test.tar.gz dest=/data/’

  • Service Module

Manages services

ansible srv -m service -a 'name=httpd state=stopped'  # Stop service
ansible srv -m service -a 'name=httpd state=started enabled=yes' # Start service and set to start on boot
ansible srv -m service -a 'name=httpd state=reloaded'  # Reload
ansible srv -m service -a 'name=httpd state=restarted' # Restart service

  1. Playbook Mode

<span>ansible-playbook -i <inventory path> <playbook file> <optional parameters></span>

Playbook Template Example

  1. Playbook to Create Directory

---
- name: Create directory
  hosts: all  # Can split backend group (backend) and frontend group (frontend)
  remote_user: root  # User executing the deployment
  vars:
    backup_dir: "/opt/backup/{{ ansible_date_time.date }}"  # Backup path (by date)
  tasks:
    # 1. Preparation: Create backup and temporary directories
    - name: Create backup directory
      file:
        path: "{{ backup_dir }}"
        state: directory
        mode: '0755'

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