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User data for cloud servers

User data is custom configuration parameters for the server operating system. You can use user data to automate server setup. Custom parameters are described as cloud-config scripts (text files with YAML syntax) or as bash scripts. The scripts are automatically encoded in Base64, sent to the server, and executed using the cloud-init agent during the first operating system boot.

Learn more about cloud-config and bash script formats in the User data formats section of the cloud-init documentation.

You can specify user data when creating a cloud server. You can pass operating system configuration parameters and scripts. For example, you can:

See other examples in the Cloud config examples section of the cloud-init documentation.

Specify user data

You can specify user data only when creating a cloud server:

  • in the Control Panel — at step 4 additional settings you can insert a script into the User data field, upload a file in txt, gz, sh format, or as a MIME archive. The maximum size of the script with data that is not Base64 encoded is 16 KB;
  • via OpenStack CLI and Terraform — only scripts with Base64 encoded data.

You cannot change the script after the server is created.

User data examples

Create a directory and upload files to it⁠

Example script to create a directory and download a file to it over a network:

#cloud-config
runcmd:
- mkdir /run/newdir
- [ wget, "http://example.com", -O, /run/newdir/index.html ]

Update repositories and install packages

Example script to install pwgen and pastebinit:

#cloud-config
package_update: true
packages:
 - pwgen
 - pastebinit

Place SSH keys on the server

Example script:

#cloud-config
ssh_authorized_keys:
  - ssh-rsa AAAAB3N…V7NZ user1@host
  - ssh-rsa AAAAB3N…NtHw== user2@server

Configure a configuration file

example script for the resolv.conf DNS resolver:

#cloud-config
manage_resolv_conf: true
resolv_conf:
  nameservers: ['4.4.4.4', '8.8.8.8']
  searchdomains:
    - foo.example.com
    - bar.example.com
  domain: example.com
  options:
    rotate: true
    timeout: 1