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Chapter 13. Preventing cloud-init from updating config files

When you create or restore an instance from a backup image, the instance ID changes. With an updated instance ID, the cloud-init utility updates configuration files. However, you can ensure that cloud-init does not update certain configuration files when you create or restore from backup.

Procedure

  1. Edit the /etc/cloud/cloud.cfg file: 

    # vi /etc/cloud/cloud.cfg

  2. Comment out or remove the configuration that you do not want cloud-init to update when you restore your instance. For example, to avoid updating the SSH key file, remove -ssh from the cloud_init_modules section. 

    cloud_init_modules:
 - disk_setup
 - migrator
 - bootcmd
 - write-files
 - growpart
 - resizefs
 - set_hostname
 - update_hostname
 - update_etc_hosts
 - rsyslog
 - users-groups
 # - ssh

Verification

  • To check the configuration files updated by cloud-init, examine the /var/log/cloud/cloud-init.log file. Updated files are logged during instance startup with messages beginning with Writing to: 

    2019-09-03 00:16:07,XXX - util.py[DEBUG]: Writing to /root/.ssh/authorized_keys - wb: [XXX] 554 bytes
2019-09-03 00:16:08,XXX - util.py[DEBUG]: Writing to /etc/ssh/sshd_config - wb: [XXX] 3905 bytes
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