Method get_esp_partition_number

crates/blockdev/src/blockdev.rs:160–186

Get the numeric partition index of the ESP (e.g. "1", "2"). We read `/sys/class/block/ /partition` rather than parsing device names because naming conventions vary across disk types (sd, nvme, dm, etc.). On multipath devices the sysfs `partition` attribute doesn't exist, so we fall back to the `partn` field reported by lsblk, then to parsing the partition suffix from the ESP device path rela

(&self)

    /// partition suffix from the ESP device path relative to the parent device
    /// path (e.g. parent `/dev/mapper/mpatha`, ESP `/dev/mapper/mpatha2` → `"2"`).
    pub fn get_esp_partition_number(&self) -> Result<String> {
        let esp_device = self.find_partition_of_esp()?;
        let devname = &esp_device.name;

        let partition_path = Utf8PathBuf::from(format!("/sys/class/block/{devname}/partition"));
        if partition_path.exists() {
            return std::fs::read_to_string(&partition_path)
                .with_context(|| format!("Failed to read {partition_path}"));
        }

        // On multipath the partition attribute is not existing
        if self.is_mpath()? {
            if let Some(partn) = esp_device.partn {
                return Ok(partn.to_string());
            }
            // Last resort: strip the parent device path from the ESP device path,
            // then skip any non-digit separator (e.g. "p") to get the partition number.
            // For example: parent "/dev/mapper/mpatha", ESP "/dev/mapper/mpatha2" → "2"
            //              parent "/dev/mapper/mpatha", ESP "/dev/mapper/mpathap2" → "2"
            let parent_path = self.path();
            let esp_path = esp_device.path();
            if let Some(n) = parse_partition_number_from_suffix(&parent_path, &esp_path) {
                return Ok(n);
            }
        }
        anyhow::bail!("Not supported for {devname}")
    }

    /// Find BIOS boot partition among children.
    pub fn find_partition_of_bios_boot(&self) -> Option<&Device> {