Add swapfile for Alibaba Cloud ECS

Ansible Playbook: Add swapfile for Alibaba Cloud ECS（幂等，适配Alinux / CentOS / Ubuntu）

阿里云ECS注意：普通云盘不建议开swap；SSD/ESSD云盘才适合。小实例（1C/2G、2C/4G）最常用；大内存机器尽量不用swap，频繁swap会IO打满卡顿。
fallocate 在部分XFS镜像不支持，playbook 优先fallocate，失败自动切dd。

add_swap_aliyun.yml

yaml
--- - name: Add swapfile on Aliyun ECS hosts: aliyun_ecs become: true gather_facts: true vars: swap_file: "/swapfile" swap_size_mb: 2048 # 2G，可自定义；内存<=2G建议2倍内存；2~8G等于内存；>8G不推荐 swappiness: 10 # aliyun推荐10，越低越优先用物理内存 vfs_cache_pressure: 50


  tasks:

    - name: Check if swapfile exists

      stat:

        path: "{{ swap_file }}"

      register: swapfile_stat
    - name: Check existing swap

      command: swapon --show

      register: swap_check

      changed_when: false

      ignore_errors: true
    - name: Create swapfile with fallocate

      command: fallocate -l {{ swap_size_mb }}M {{ swap_file }}

      when: not swapfile_stat.stat.exists

      register: fallocate_res

      failed_when: false
    - name: Fallocate failed, use dd fallback

      command: dd if=/dev/zero of={{ swap_file }} bs=1M count={{ swap_size_mb }} status=none

      when: >

        not swapfile_stat.stat.exists

        and fallocate_res is failed
    - name: Set swapfile permission 0600

      file:

        path: "{{ swap_file }}"

        mode: '0600'

        owner: root

        group: root
    - name: Make swap filesystem

      command: mkswap {{ swap_file }}

      when: not swapfile_stat.stat.exists
    - name: Enable swap

      command: swapon {{ swap_file }}

      when: not swapfile_stat.stat.exists
    - name: Add swap to /etc/fstab (idempotent)

      mount:

        path: none

        src: "{{ swap_file }}"

        fstype: swap

        opts: sw

        state: present
    - name: Set vm.swappiness in sysctl

      sysctl:

        name: vm.swappiness

        value: "{{ swappiness }}"

        state: present

        reload: true
    - name: Set vm.vfs_cache_pressure

      sysctl:

        name: vm.vfs_cache_pressure

        value: "{{ vfs_cache_pressure }}"

        state: present

        reload: true
    - name: Verify swap status

      command: free -h

      changed_when: false

      register: free_out

- name: Print swap result debug: msg: "{{ free_out.stdout_lines }}"
执行命令

bash

ansible-playbook -i inventory.ini add_swap_aliyun.yml

inventory.ini 示例：
ini

[aliyun_ecs] ecs-01 ansible_host=shturl.cc/dueD ansible_user=root ansible_ssh_private_key_file=~/.ssh/id_rsa

验证（在ECS内）

bash

swapon –show
free -h
cat /proc/sys/vm/swappiness

回滚/删除swap playbook片段（如需）

yaml
- name: Remove swapfile become: true tasks: - name: swapoff command: swapoff /swapfile - name: Remove fstab entry mount: path: none src: /swapfile state: absent - name: Delete swapfile file: path: /swapfile state: absent

阿里云ECS重要提醒

1. 普通高效云盘不要开swap，IO性能差，一旦频繁换页直接卡死实例；ESSD/SSD才适合
2. 预留磁盘空间：创建swap后剩余磁盘至少保留5GB空闲，否则风险高
3. 容器环境尽量不要在容器内部配置swap，在宿主机层面管理
4. swappiness=10 适合阿里云小实例，尽量减少磁盘交换

如果你需要，我可以改成根据ECS内存自动计算swap大小（不用手动写swap_size_mb，自动按内存判断）的版本。