In ansible, only when can realize conditional judgment
tasks:
- name: config the yum repo for centos 7
yum_repository:
name: epel
description: epel
baseurl: http://mirrors.aliyun.com/epel/7/$basearch/
gpgcheck: no
when: ansible_distribution_major_version == "7"
Pay attention to two points:
The object judged by when is task , so it is at the same list level as task . The result of its judgment determines whether the task it is in is executed, not whether the task below it is executed.
There is no need to add {{ }} symbols when referencing variables in when .
(1) When no conditions are set, two servers execute commands at the same time, how to set only 192.168.20.42 to execute operation commands
(2) Configure playbook
[root@k8s-master2 install]# more when.yaml
---
- hosts: webservers
remote_user: root
gather_facts: true
tasks:
-name: Only the 192.168.20.42 host is allowed to execute
debug: msg="{{ansible_default_ipv4.address}}"
when: ansible_default_ipv4.address == '192.168.20.42'
(3) Perform operation:
[root@k8s-master2 install]# ansible-playbook when.yaml
The result skipped 43 servers and executed directly on 42 servers
2. Cycle: Create users in batches
[root@k8s-master2 install]# more user.yaml
---
- hosts: webservers
remote_user: root
gather_facts: true
tasks:
-name: all hosts execute
user: name={{ item }} state=present
with_items:
- user1
- user2
- hahashen
[root@k8s-master2 install]# ansible-playbook -C user.yaml
[root@k8s-master2 install]# ansible-playbook user.yaml
verification:
192.168.20.41
[root@k8s-node1 ~]# tail -n 3 /etc/passwd
user1:x:1001:1001::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
hahashen:x:1003:1003::/home/hahashen:/bin/bash
192.168.20.42
[root@k8s-node2 ~]# tail -n 3 /etc/passwd
user1:x:1001:1001::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
hahashen:x:1003:1003::/home/hahashen:/bin/bash
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