grub-render-label

grub-render-label STRING

STRING
    The string to render as a label. This can contain variables, shell commands, and conditional statements that are evaluated to generate the final label.

The `grub-render-label` command is a utility provided by GRUB (GRand Unified Bootloader) for rendering the labels associated with menu entries. It's primarily used internally by GRUB's configuration scripts to dynamically generate readable and user-friendly labels for boot options. The command takes a string as input, which represents a GRUB identifier or some other data to be rendered. The labels can incorporate variables, shell commands, and conditional logic, allowing for flexible and informative menu displays.

Typically, `grub-render-label` is not directly invoked by end-users. Instead, it's used in conjunction with other GRUB utilities and configuration files (like `grub.cfg`) to customize the boot menu appearance. The command is vital to displaying descriptive names for operating systems, kernel versions, and recovery options at boot time. It relies heavily on the environment and variables set up during GRUB's configuration generation process. By interpreting these variables and executing commands embedded in the input string, `grub-render-label` transforms a potentially cryptic identifier into a human-readable string. This is useful for improving usability and navigability of the boot menu.

This command is intended for use within GRUB configuration scripts and not for direct user interaction. Its behavior is heavily dependent on the GRUB environment and variables available at the time of execution.

The STRING argument can contain GRUB environment variables that are dynamically replaced with their values. For example, `${kernel}` might be replaced with the actual kernel version being booted.

The STRING argument may also include shell commands enclosed in `${exec command}`. The output of these commands is then substituted into the label. Example: `${exec cat /etc/os-release | grep PRETTY_NAME | cut -d '=' -f 2 | tr -d '"'}`

GRUB supports conditional statements within the STRING argument, such as `if`, `else`, and `fi`. These allow the label to be dynamically generated based on system conditions.
For Example: `if [ "${grub_platform}" == "efi" ]; then echo EFI; else echo BIOS; fi`

The `grub-render-label` command was introduced as part of the GRUB 2 (GRUB 2) rewrite. It replaced functionality that was available through older GRUB versions, making the configuration process more dynamic and flexible. Before GRUB 2, the labels were often statically coded into the configuration file. The development of `grub-render-label` significantly improved the user experience by allowing labels to reflect the underlying system configuration. Usage has increased in time as distributions adopted GRUB 2 as its default bootloader.

grub-mkconfig(8), grub-install(8), grub.cfg(5)