Ansible common usage scenarios

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to Ansible The next complete definition is difficult , The official propaganda is Ansible is Simple IT Automation It seems that automation is still the main focus .

Ansible delivers simple IT automation that ends repetitive tasks and frees up DevOps teams for more strategic work.

There is also information Ansible Is a model driven configuration manager , Personally, I don't think this description is very appropriate . from Ansible In terms of the use of , By default push The way is more like Automation . and Puppet By default pull The way , It is more like configuration driver .

Ansible There are two modes of using , One is to call the module directly on the command line to execute a single command in batch , This is called AD HOC Pattern .

$ ansible [host_inventory] -m command -a 'hostname'

You can also write yaml file , To orchestrate a set of operations , This is called playbook Pattern . Look at a simple configuration .

# test.yaml
---
- hosts: 192.168.1.31
  remote_user: root
  tasks: 
    - name: run df -h
      remote_user: test
      shell: name=df -h

This is how it is used ,AD HOC Patterns cannot be persisted ,playbook The way can be through yaml File persistence and repeated execution .

$ ansible-playbook test.yaml

Today, let's get familiar with some of the most commonly used modules ：

command modular

Execute command on remote node , Use as follows ：

$ ansible [host_list] -m command -a "hostname"

But this way is not to call shell Environment to execute orders , So we can't get environment variables , You cannot use pipe symbols 、 Redirect etc. .

Support chdir Parameters , That is, switch to the specified directory before executing the command .

$ ansible [host_list] -m command -a "ls -l chdir=/etc/yum.repos.d"
# command  yes  ansible  Default module for , It can be omitted 
$ ansible [host_list] -a "ls -l chdir=/etc/yum.repos.d"

shell modular

If you need to be in the remote shell Give orders , You need to use shell modular . Usage and command identical , But it is called when the command is executed /bin/sh

$ ansible [host_list] -m command -a 'echo $LOGNAME'
#  This command can print the currently logged in user name 
$ ansible [host_list] -m command -a 'ps -ef | grep java | wc -l'
#  This command can count the  java  Number of programs 

copy modular

Copy file , Support local replication to the server .

#  Copy files from the server to the managed machine 
$ ansible [host_list] -m copy -a 'src=/etc/hosts dest=/tmp owner=root mode=0755'

#  Save the content as a remote file 
$ ansible [host_list] -m copy -a 'content=Hello World! desc/tmp/test.txt owner=root force=yes mode=0755'

fetch modular

Get file from remote , If dest When specified as a folder , The default is based on IP Create a folder for the name , Relevant files are saved in the corresponding folder .

#  Get the file from the remote server 
$ ansible [host_list] -m fetch -a 'src=/etc/hosts dest=/home/path owner=root mode=0755'

parameter list ：

• dest ： The directory where the target is stored . If you get /etc/hosts The target is stored in /home Next , The final save path is /home/host.example.com/etc/hosts, The host name is based on /etc/ansible/hosts Configuration of .
• src ： At present, it can only be files .

Common user execution Ansible Problems encountered

Scenario as follows , Manager of root The account number was collected , I can only use ordinary users shiqiang perform ansible command . here , If the host list is configured as follows ：

$ cat /etc/ansible/hosts
[testhost]
128.128.128.128
$ ansible testhost -m ping

Will be submitted to the Permission Denied Error of . The reason is to use shiqiang This account executes ansible On command , By default, the current user will try to log in to the target host without secret . because testhost The host and the management machine have done root Mutual trust of account ,, In this case, the use of root user , At the same time, the management machine shiqiang User id_rsa.pub copy to testhost Of .ssh/authorized_keys In file .

$ cat /etc/ansible/hosts
[testhost]
128.128.128.128 ansible_ssh_user=root 

Reference material

1. Ansible Copy files or directories
2. Ansible Common modules
3. Ansible Command module
4. How Ansible Works
5. Ansible And Playbook
6. Ansible Copy files to local
7. Linux Realize password free login and execution of ordinary users under root jurisdiction