The user data of Elastic Compute Service (ECS) instances can be used to manage startups of the instances or pass data into the instances.
- User data can be run as scripts on instance startup to automate instance configurations such as automatically obtaining software resource packages, enabling services, printing logs, installing dependencies, and initializing web environments.
- User data can be used as common data and passed into instances for use.
You can prepare user data by using different types of scripts. After you prepare the user data, you can pass it into an instance by entering the script content when you create the instance. For more information, see Manage user data of Linux instances and Manage user data of Windows instances.
You can view the user data that has been passed into an instance by using the metadata of the instance. For more information, see View instance metadata.
- The user data feature is supported only for instances that reside in virtual private clouds (VPCs).
- The instances must be created from the following public images or custom images derived from public images:
- Alibaba Cloud Linux, CentOS, CentOS Stream, Ubuntu, SUSE Linux Enterprise Server, Red Hat Enterprise Linux, OpenSUSE, Debian, AlmaLinux, Rocky Linux, and Fedora
- Windows Server 2008 R2 and later
- The user data feature is supported for all available instance types. For retired instance types, the user data feature is supported only for I/O-optimized instances. For more information, see Retired instance types.
- The user data that you want to run must be encoded in Base64. The size of the user data cannot exceed 16 KB before it is encoded. Note You can enter the user data that has not been encoded in Base64 in the console. The console automatically encodes the user data in Base64. If you do not want to enter the user data in the console, you must encode it in Base64 on your own.