openstack 密码注入之cloud-init 简单介绍

迷南。 2022-06-18 11:07 934阅读 0赞

首先这里我们配置metadata注入方式为config driver这样就可以不用依赖网络不用再通过[http://169.254.169.254][http_169.254.169.254]去获取metadata  
计算节点修改配置：  
vi /etc/nova/nova.conf  
force\_config\_drive=True  
执行命令：  
service nova-compute restart  
在我们创建完虚拟机之后，若我们后端存储是ceph则xml中会有如下字段：

若使用本地存储，则会有如下字段：

这就是所谓的config driver那块盘  
如下图所示，虚拟机镜像安装完cloud-init之后会有相应服务：  
![这里写图片描述][SouthEast]  
这三个服务开机启动，第一次开机时会进行相应的metadata的解析，根据配置我们使用config driver的话则会相应进行解析config driver的工作，如下举例：

[root@test-for-qos ~]# cat /usr/lib/systemd/system/cloud-init.service
    [Unit]
    Description=Initial cloud-init job (metadata service crawler)
    After=local-fs.target network.target cloud-init-local.service
    Requires=network.target
    Wants=local-fs.target cloud-init-local.service
    
    [Service]
    Type=oneshot
    ExecStart=/usr/bin/cloud-init init
    RemainAfterExit=yes
    TimeoutSec=0
    
    # Output needs to appear in instance console output
    StandardOutput=journal+console
    
    [Install]
    WantedBy=multi-user.target

根据cloud-init的步骤：

# Cloud-init 'init' stage is broken up into the following sub-stages
        # 1. Ensure that the init object fetches its config without errors
        # 2. Setup logging/output redirections with resultant config (if any)
        # 3. Initialize the cloud-init filesystem
        # 4. Check if we can stop early by looking for various files
        # 5. Fetch the datasource
        # 6. Connect to the current instance location + update the cache
        # 7. Consume the userdata (handlers get activated here)
        # 8. Construct the modules object
        # 9. Adjust any subsequent logging/output redirections using the modules
        #    objects config as it may be different from init object
        # 10. Run the modules for the 'init' stage
        # 11. Done!

我们就直接进入第5步：  
![这里写图片描述][SouthEast 1]  
主要实现取数据的地方是get\_data函数  
然后通过进入函数mount\_cb  
![这里写图片描述][SouthEast 2]  
![这里写图片描述][SouthEast 3]  
实现机制就是通过blkid -odevice -tLABEL=config-2找到盘vdb，然后创建临时目录并将其挂载即可读取相应数据

[http_169.254.169.254]: http://169.254.169.254
[SouthEast]: /images/20220618/c460a5572f764792b0e70779314fa8c6.png
[SouthEast 1]: /images/20220618/a15d64fa646242618b52a60462580025.png
[SouthEast 2]: /images/20220618/a3fdddad80084197844d45d57e36414e.png
[SouthEast 3]: /images/20220618/9ea71031626c40d6ad0f17c2fd170adf.png