User data in the cloud server

Last update: May 27 2025

User data in the cloud server

User data — user configuration parameters of the server operating system. With the help of user data you can automate server configuration. User parameters are described as scripts in cloud-config format (text files with YAML syntax) or as a bash script. The scripts are automatically Base64 encoded, transferred to the server, and executed by the cloud-init agent when the operating system is first started.

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

You can specify user data can be specified when creating a cloud server. In scripts, you can pass parameters to configure the operating system and scripts. For example:

• create a directory and upload files to it;
• update repositories and install software packages;
• to place SSH keys on the server;
• configure the domain name resolver configuration file resolv.conf.

See more examples in the Cloud config examples documentation cloud-init instructions.

Specify user data⁠

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

• in the control panel — at step 4 of additional settings you can insert a script in the User data field, upload a file in txt, gz, sh or MIME-archive formats. The maximum size of a script with non-Base64 encoded data is 16 KB;
• through OpenStack CLI and Terraform — only scripts with Base64 encoded data.

Once the server is created, you cannot change the script.

Examples of user data⁠

Create a directory and upload files to it⁠

Cloud-config

An example script to create a directory and upload a file to it over the network:

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

Bash script

An example script to create a directory and upload a file to it over the network:

#!/bin/sh
mkdir /run/newdir
wget http://example.com -O /run/newdir/index.html

Update repositories and install packages⁠

Cloud-config

Sample script to install pwgen and pastebinit:

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

Bash script

An example script for installing docker:

#!/bin/sh
apt update
apt install docker

Place SSH keys on the server⁠

Cloud-config

Sample script:

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

Bash script

Sample script:

#!/bin/sh
echo "ssh-rsa AAAAB3N…V7NZ user1@host" >> /root/.ssh/authorized_keys
echo "sssh-rsa AAAAB3N…NtHw== user2@server" >> /root/.ssh/authorized_keys

Customize the configuration file⁠

Cloud-config

Sample script for the resolv.conf domain name 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

Bash script

Sample script for the resolv.conf domain name resolver:

#!/bin/sh
cat <<EOF > /etc/resolv.conf
domain example.com
nameserver 4.4.4.4
nameserver 8.8.8.8
search foo.example.com bar.example.com
options rotate
options timeout:1
EOF