Help Center/ Elastic Cloud Server/ User Guide/ Instances/ Managing ECS Configurations/ Obtaining Metadata and Passing User Data/ Injecting User Data

Updated on 2025-08-12 GMT+08:00

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Injecting User Data

Scenarios

Specify User Data to inject user data into ECSs to:

Simplify ECS configuration.
Initialize the ECS OS configuration.
Upload your scripts to ECSs during ECS creation.
Perform other tasks using scripts.

Constraints

Linux
- The image that is used to create ECSs must have Cloud-Init installed.
- The user data to be specified must be less than or equal to 32 KB.
- If user data is uploaded as text, the data can contain only ASCII characters. If user data is uploaded using a file, the file can contain any characters and the file size cannot exceed 32 KB.
- The image that is used to create ECSs must be a public image, a private image created from a public image, or a private image with Cloud-Init installed.
- The format of the user data scripts must be supported by Linux ECSs.
- DHCP must be enabled on the VPC network, and port 80 must be enabled for the security group in the outbound direction.
- When the password login mode is selected, user data cannot be injected.
Windows
- The image that is used to create ECSs must have Cloudbase-Init installed.
- The user data to be specified must be less than or equal to 32 KB.
- If user data is uploaded as text, the data can contain only ASCII characters. If user data is uploaded using a file, the file can contain any characters and the file size cannot exceed 32 KB.
- The image that is used to create ECSs must be a public image, a private image created based on a public image, or a private image with Cloudbase-Init installed.
- DHCP must be enabled on the VPC network, and port 80 must be enabled for the security group in the outbound direction.

Injecting User Data

Create a user-data script that complies with user-data script specifications. For details, see Helpful Links.
When creating an ECS, set Advanced Options to Configure now, and paste the content of the user data script to the User Data text box or upload the user data file.

You can inject user data to an ECS as text or as a file.

Text: Copy the content of the user data script to the text box.

File: Save the user data script to a text file and then upload the file.

Figure 1 User data injection
The created ECS automatically runs Cloud-Init or Cloudbase-Init and reads the user data script upon startup.

User Data Scripts of Linux ECSs

User data scripts (referred to as scripts) of Linux ECSs are based on the open-source Cloud-Init architecture. This architecture uses ECS metadata as the data source for configuring the ECSs. User data scripts are compatible with the open-source Cloud-Init. For details about Cloud-Init, see http://cloudinit.readthedocs.io/en/latest/topics/format.html.

Script execution time: A user data script is executed after the status of the target ECS changes to Running and before /etc/init is executed.

By default, the scripts are executed as user root.

Script types: user-data and Cloud-Config data scripts

**Table 1** Linux ECS script types
Item	User-Data Script	Cloud-Config Data Script
Description	Scripts, such as Shell and Python scripts, are used for custom configurations.	Methods pre-defined in Cloud-Init, such as the yum repository and SSH key, are used for configuring certain ECS applications.
Format	The first line must start with #! (for example, #!/bin/bash or #!/usr/bin/env python), and no spaces are allowed at the beginning. When a script is started for the first time, it will be executed at the rc.local-like level, indicating a low priority in the boot sequence.	The first line must be #cloud-config, and no space is allowed in front of it.
Constraint	Before Base64 encoding, the size of the script, including the first line, cannot exceed 32 KB.	Before Base64 encoding, the size of the script, including the first line, cannot exceed 32 KB.
Frequency	The script is executed only once when the ECS is started for the first time.	The execution frequency varies according to the applications configured on the ECS.

How can I view the user data injected into a Linux ECS?
1. Log in to the ECS.
2. Run the following command to view the user data as user root:
  curl http://169.254.169.254/openstack/latest/user_data
Script usage examples
The following describes how to inject scripts in different formats into Linux ECSs and view script execution results.

Example 1: Inject a user-data script.

When creating an ECS, set User Data to As text and enter the user data script.
```
#!/bin/bash
echo "Hello, the time is now $(date -R)" | tee /root/output.txt
```
After the ECS is created, start it and run the cat [file] command to check the script execution result.
```
[root@XXXXXXXX ~]# cat /root/output.txt
Hello, the time is now Mon, 16 Jul 2016 16:03:18+0800
```
Example 2: Inject a Cloud-Config data script.

When creating an ECS, set User Data to As text and enter the user data script.
```
#cloud-config
bootcmd:
- echo 192.168.1.130 us.archive.ubuntu.com >> /etc/hosts
```
After the ECS is created, start it and run the cat /etc/hosts command to check the script execution result.

Figure 2 Viewing operating results

User Data Scripts of Windows ECSs

User data scripts of Windows ECSs are based on the open-source Cloudbase-Init architecture. This architecture uses ECS metadata as the data source for initializing and configuring the ECSs. User data scripts are compatible with the open-source Cloudbase-Init. For details about Cloudbase-Init, see https://cloudbase-init.readthedocs.io/en/latest/userdata.html.

Script types: batch-processing program and PowerShell scripts

**Table 2** Windows ECS script types
Item	Batch-Processing Program Script	PowerShell Script
Format	The script must start with rem cmd and use it as the first line. No space is allowed at the beginning of the first line.	The script must start with #ps1 and use it as the first line. No space is allowed at the beginning of the first line.
Constraint	Before Base64 encoding, the size of the script, including the first line, cannot exceed 32 KB.	Before Base64 encoding, the size of the script, including the first line, cannot exceed 32 KB.

How can I view the user data injected into a Windows ECS?
1. Log in to the ECS.
2. In the address bar of a browser, access the following URL and view the user data:
  http://169.254.169.254/openstack/latest/user_data
Script usage examples
The following describes how to inject scripts in different formats into Windows ECSs and view script execution results.

Example 1: Inject a batch-processing program script.

When creating an ECS, set User Data to As text and enter the user data script.
```
rem cmd
echo "Hello, BAT Test" > C:\1111.txt
```
After the ECS is created, start it and check the script execution result. In this example, a text file named 1111 is added to disk C:\.

Figure 3 Creating text file (Batch)

To view the user data injected into the Windows ECS, log in at http://169.254.169.254/openstack/latest/user_data.

Figure 4 Viewing user data (Batch)

Example 2: Inject a PowerShell script.

When creating an ECS, set User Data to As text and enter the user data script.
```
#ps1
echo "Hello, Powershell Test" > C:\aaaa.txt
```
After the ECS is created, start it and check the script execution result. In this example, a text file named aaaa is added to disk C:\.

Figure 5 Creating text file (PowerShell)

To view the user data injected into the Windows ECS, log in at http://169.254.169.254/openstack/latest/user_data.

Figure 6 Viewing user data (PowerShell)

Case 1

This case illustrates how to inject user data to simplify Linux ECS configurations.

In Vim, to enable syntax highlighting, display line numbers, and set tab to 4 spaces, create a .vimrc script and inject it into the /root/.vimrc directory during ECS creation. After the ECS is created, vim is automatically configured based on your requirements. This improves ECS configuration efficiency, especially in batch ECS creation scenarios.

User data example:

#cloud-config
write_files:
  - path: /root/.vimrc
    content: |
      syntax on
      set tabstop=4
      set number

Case 2

This case illustrates how to use the user data injection function to set the password for logging in to a Linux ECS.

The new password must meet the password complexity requirements listed in Table 3.

**Table 3** Password complexity requirements
Parameter	Requirement
Password	Consists of 8 to 26 characters. Contains at least three of the following character types: Uppercase letters Lowercase letters Digits Special characters for Linux: !@$%^-_=+[{}]:,./?~#* Cannot contain the username or the username spelled backwards.

User data example:

Using a ciphertext password (recommended)

#!/bin/bash 
echo 'root:$6$V6azyeLwcD3CHlpY$BN3VVq18fmCkj66B4zdHLWevqcxlig' | chpasswd -e;

In this command, $6$V6azyeLwcD3CHlpY$BN3VVq18fmCkj66B4zdHLWevqcxlig is the ciphertext password, which can be generated by performing the following steps:

Run the following command to generate an encrypted ciphertext value:
python -c "import crypt, getpass, pwd;print crypt.mksalt()"

The following information is displayed:
```
$6$V6azyeLwcD3CHlpY
```
Run the following command to generate a ciphertext password based on the salt value:
python -c "import crypt, getpass, pwd;print crypt.crypt('Cloud.1234','\$6\$V6azyeLwcD3CHlpY')"

The following information is displayed:
```
$6$V6azyeLwcD3CHlpY$BN3VVq18fmCkj66B4zdHLWevqcxlig
```

After the ECS is created, you can use the password to log in to it.

When you specify the adminPass field during Linux ECS creation, you can refer to this example to set the password for the ECS through user data injection.

Case 3

This case illustrates how to use the user data injection function to reset the password for logging in to a Linux ECS.

In this example, the password of user root is reset to ******.

The new password must meet the password complexity requirements listed in Table 4.

**Table 4** Password complexity requirements
Parameter	Requirement
Password	Consists of 8 to 26 characters. Contains at least three of the following character types: Uppercase letters Lowercase letters Digits Special characters for Linux: !@$%^-_=+[{}]:,./?~#* Cannot contain the username or the username spelled backwards.

User data example (Retain the indentation in the following script):

#cloud-config
chpasswd:
  list: |
    root:******
  expire: False

After the ECS is created, you can use the reset password to log in to it. To ensure system security, change the password of user root after logging in to the ECS for the first time.

Case 4

This case illustrates how to use the user data injection function to create a user on a Windows ECS and configure the password for the user.

In this example, the user's username is abc, its password is ******, and the user is added to the administrators user group.

The new password must meet the password complexity requirements listed in Table 4.

User data example:

rem cmd
net user abc ****** /add
net localgroup administrators abc /add

After the ECS is created, you can use the created username and password to log in to it.

Case 5

This case illustrates how to use the user data injection function to update system software packages for a Linux ECS and enable the httpd service. After the user data is injected to an ECS, you can use the httpd service.

User data example:

#!/bin/bash
yum update -y
service httpd start
chkconfig httpd on

Case 6

This case illustrates how to use the user data injection function to assign user root permissions for remotely logging in to a Linux ECS. After the user data is injected to an ECS, you can log in to the ECS as user root using SSH key pair authentication.

User data example:

#cloud-config
disable_root: false
runcmd:
- sed -i 's/^PermitRootLogin.*$/PermitRootLogin without-password/' /etc/ssh/sshd_config
- sed -i '/^KexAlgorithms.*$/d' /etc/ssh/sshd_config
- service sshd restart