Constant KTSTR_BUSYBOX_PATH_ENV 

pub const KTSTR_BUSYBOX_PATH_ENV: &str = "KTSTR_BUSYBOX_PATH";

Name of the environment variable that points at the busybox blob on-disk. Exported by cargo-ktstr’s startup install_env (see bin/cargo_ktstr/blobs.rs) which extracts the embedded BUSYBOX_BYTES to a tempfile and sets this var to the absolute path; read by crate::vmm::blobs::load_busybox_bytes. Both unset and set-but-empty surface a hard error, BUT the diagnostic differs: unset hits the Err(_) arm and surfaces the “blob is provided by cargo-ktstr at startup” install-env hint; empty hits the Ok("") arm and falls through to a generic fs::read("") ENOENT — less actionable. Operators invoking cargo ktstr <SUB> see neither case; raw cargo nextest run reliably triggers the unset diagnostic. Busybox is load-bearing for shell-mode VMs + disk-template builds.