Function have_udev

crates/blockdev/src/blockdev.rs:24–35

Check whether the udev database is accessible (cached for the process lifetime). When running inside a container or sandbox without `/run/udev` bind-mounted, tools like `lsblk` that depend on the udev database will return null for fields like `parttype` and `fstype`. We check for `/run/udev/data` (the actual database directory) rather than just `/run/udev` because the parent directory can exist

()

/// than just `/run/udev` because the parent directory can exist as an
/// empty mount point without the database being populated.
fn have_udev() -> bool {
    static HAVE_UDEV: OnceLock<bool> = OnceLock::new();
    *HAVE_UDEV.get_or_init(|| {
        let r = Path::new("/run/udev/data").exists();
        if !r {
            tracing::debug!(
                "udev database not available, will use blkid -p for partition metadata"
            );
        }
        r
    })
}

/// Probe a device with `blkid -p` and return all discovered properties
/// as key-value pairs.