You can customize the personality of a server instance by injecting data into its file system. For example, you might want to insert ssh keys, set configuration files, or store data that you want to retrieve from inside the instance. This feature provides a minimal amount of launch-time personalization. If you require significant customization, create a custom image.
Follow these guidelines when you inject files:
The maximum size of the file path data is 255 bytes.
Encode the file contents as a Base64 string. The maximum size of the file contents is determined by the compute provider and may vary based on the image that is used to create the server
![[Note]](../common/images/admon/note.png)
Note The maximum limit refers to the number of bytes in the decoded data and not the number of characters in the encoded data.
You can inject text files only. You cannot inject binary or zip files into a new build.
The maximum number of file path/content pairs that you can supply is also determined by the compute provider and is defined by the maxPersonality absolute limit.
The absolute limit, maxPersonalitySize, is a byte limit that is guaranteed to apply to all images in the deployment. Providers can set additional per-image personality limits.
The file injection might not occur until after the server is built and booted.
During file injection, any existing files that match specified files are renamed to include the bak extension appended with a time stamp. For example, if the file /etc/passwd exists, it is backed up as /etc/passwd.bak.1246036261.5785.
After file injection, personality files are accessible by only system administrators. For example, on Linux, all files have root and the root group as the owner and group owner, respectively, and allow user and group read access only ( ).
