Function write_grub_uki_menuentry

crates/lib/src/bootc_composefs/boot.rs:916–997

(
    root_path: Utf8PathBuf,
    setup_type: &BootSetupType,
    boot_label: String,
    id: &Sha512HashValue,
    esp_device: &String,
)

#[context("Writing Grub menuentry")]
fn write_grub_uki_menuentry(
    root_path: Utf8PathBuf,
    setup_type: &BootSetupType,
    boot_label: String,
    id: &Sha512HashValue,
    esp_device: &String,
) -> Result<()> {
    let boot_dir = root_path.join("boot");
    create_dir_all(&boot_dir).context("Failed to create boot dir")?;

    let is_upgrade = matches!(setup_type, BootSetupType::Upgrade(..));

    let efi_uuid_source = get_efi_uuid_source();

    let user_cfg_name = if is_upgrade {
        USER_CFG_STAGED
    } else {
        USER_CFG
    };

    let grub_dir = Dir::open_ambient_dir(boot_dir.join("grub2"), ambient_authority())
        .context("opening boot/grub2")?;

    // Iterate over all available deployments, and generate a menuentry for each
    if is_upgrade {
        let mut str_buf = String::new();
        let boot_dir =
            Dir::open_ambient_dir(boot_dir, ambient_authority()).context("Opening boot dir")?;
        let entries = get_sorted_grub_uki_boot_entries(&boot_dir, &mut str_buf)?;

        grub_dir
            .atomic_replace_with(user_cfg_name, |f| -> std::io::Result<_> {
                f.write_all(efi_uuid_source.as_bytes())?;
                f.write_all(
                    MenuEntry::new(&boot_label, &id.to_hex())
                        .to_string()
                        .as_bytes(),
                )?;

                // Write out only the currently booted entry, which should be the very first one
                // Even if we have booted into the second menuentry "boot entry", the default will be the
                // first one
                f.write_all(entries[0].to_string().as_bytes())?;

                Ok(())
            })
            .with_context(|| format!("Writing to {user_cfg_name}"))?;

        rustix::fs::fsync(grub_dir.reopen_as_ownedfd()?).context("fsync")?;

        return Ok(());
    }

    // Open grub2/efiuuid.cfg and write the EFI partition fs-UUID in there
    // This will be sourced by grub2/user.cfg to be used for `--fs-uuid`
    let esp_uuid = Task::new("blkid for ESP UUID", "blkid")
        .args(["-s", "UUID", "-o", "value", &esp_device])
        .read()?;