feat(cli):Add install-to-filesystem to copy file

Add cli `bootupctl backend install-to-filesystem` command,
making file copying more robust and user-friendly.

Key feature:

- Flexible source paths: The `--file-path` now correctly handles an
  optional leading slash (`/`), always interpreting the path as
  relative to `src_root`.
- Recursive destination dirs: Automatically creates the full parent
  directory structure in the destination (like `mkdir -p`), preventing
  errors from missing intermediate directories. This is idempotent.
- Reliable file overwriting: Existing destination files are overwritten.
- Improved ESP path logic: More robustly determines destination paths
  relative to the mounted ESP root when `--file-path` targets ESP content.

Example:
  bootupctl backend install-to-filesystem \
    --src-root /boot \
    --file-path firmware/efi/somefile.bin \
    /mnt/target_destination

Author: say-paul

src/cli/bootupctl.rs

@@ -73,6 +73,8 @@ pub enum CtlBackend {
     Generate(super::bootupd::GenerateOpts),
     #[clap(name = "install", hide = true)]
     Install(super::bootupd::InstallOpts),
+    #[clap(name = "install-to-filesystem", hide = true)]
+    InstallToFilesystem(super::bootupd::InstallToFilesystemOpts),
 }
 
 #[derive(Debug, Parser)]
@@ -102,6 +104,9 @@ impl CtlCommand {
             CtlVerb::Backend(CtlBackend::Install(opts)) => {
                 super::bootupd::DCommand::run_install(opts)
             }
+            CtlVerb::Backend(CtlBackend::InstallToFilesystem(opts)) => {
+                super::bootupd::DCommand::run_install_to_filesystem(opts)
+            }
             CtlVerb::MigrateStaticGrubConfig => Self::run_migrate_static_grub_config(),
         }
     }

src/cli/bootupd.rs

@@ -35,6 +35,11 @@ pub enum DVerb {
     GenerateUpdateMetadata(GenerateOpts),
     #[clap(name = "install", about = "Install components")]
     Install(InstallOpts),
+    #[clap(
+        name = "install-to-filesystem",
+        about = "Copy files between directories with ESP handling"
+    )]
+    InstallToFilesystem(InstallToFilesystemOpts),
 }
 
 #[derive(Debug, Parser)]
@@ -82,16 +87,29 @@ pub struct GenerateOpts {
     sysroot: Option<String>,
 }
 
+#[derive(Debug, Parser)]
+pub struct InstallToFilesystemOpts {
+    #[clap(long, default_value_t = String::from("/") , help = "Source root directory")]
+    src_root: String,
+
+    #[clap(long, help = "Destination root directory")]
+    dest_root: String,
+
+    #[clap(value_parser, help = "file relative path")]
+    file_path: String,
+}
+
 impl DCommand {
     /// Run CLI application.
     pub fn run(self) -> Result<()> {
         match self.cmd {
             DVerb::Install(opts) => Self::run_install(opts),
             DVerb::GenerateUpdateMetadata(opts) => Self::run_generate_meta(opts),
+            DVerb::InstallToFilesystem(opts) => Self::run_install_to_filesystem(opts),
         }
     }
 
-    /// Runner for `generate-install-metadata` verb.
+    /// Runner for `generate-install-metadata` verb.``
     pub(crate) fn run_generate_meta(opts: GenerateOpts) -> Result<()> {
         let sysroot = opts.sysroot.as_deref().unwrap_or("/");
         if sysroot != "/" {
@@ -122,4 +140,9 @@ impl DCommand {
         .context("boot data installation failed")?;
         Ok(())
     }
+
+    pub(crate) fn run_install_to_filesystem(opts: InstallToFilesystemOpts) -> Result<()> {
+        crate::filesystem::copy_files(&opts.src_root, &opts.dest_root, &opts.file_path)?;
+        Ok(())
+    }
 }

src/filesystem.rs

@@ -5,9 +5,14 @@ use std::process::Command;
 use anyhow::Result;
 use bootc_utils::CommandRunExt;
 use fn_error_context::context;
+use openat_ext::OpenatDirExt;
 use rustix::fd::BorrowedFd;
 use serde::Deserialize;
 
+use crate::blockdev;
+use crate::efi::Efi;
+use std::path::Path;
+
 #[derive(Deserialize, Debug)]
 #[serde(rename_all = "kebab-case")]
 #[allow(dead_code)]
@@ -38,3 +43,260 @@ pub(crate) fn inspect_filesystem(root: &openat::Dir, path: &str) -> Result<Files
         .next()
         .ok_or_else(|| anyhow::anyhow!("findmnt returned no data"))
 }
+
+#[context("Copying {file_path} from {src_root} to {dest_root}")]
+pub(crate) fn copy_files(src_root: &str, dest_root: &str, file_path: &str) -> Result<()> {
+    let src_dir = openat::Dir::open(src_root)?;
+    let file_path = file_path.strip_prefix("/").unwrap_or(file_path);
+    let dest_dir = if file_path.starts_with("boot/efi") {
+        let efi = Efi::default();
+        match blockdev::get_single_device("/") {
+            Ok(device) => {
+                let esp_device = blockdev::get_esp_partition(&device)?;
+                let esp_path = efi.ensure_mounted_esp(
+                    Path::new(dest_root),
+                    Path::new(&esp_device.unwrap_or_default()),
+                )?;
+                openat::Dir::open(&esp_path)?
+            }
+            Err(e) => anyhow::bail!("Unable to find device: {}", e),
+        }
+    } else {
+        openat::Dir::open(dest_root)?
+    };
+
+    let src_meta = src_dir.metadata(file_path)?;
+    match src_meta.simple_type() {
+        openat::SimpleType::File => {
+            let parent = Path::new(file_path).parent().unwrap_or(Path::new("."));
+            if !parent.as_os_str().is_empty() {
+                dest_dir.ensure_dir_all(parent, 0o755)?;
+            }
+            src_dir.copy_file_at(file_path, &dest_dir, file_path)?;
+            log::info!("Copied file: {} to destination", file_path);
+        }
+        openat::SimpleType::Dir => {
+            anyhow::bail!("Unsupported copying of Directory {}", file_path)
+        }
+        openat::SimpleType::Symlink => {
+            anyhow::bail!("Unsupported symbolic link {}", file_path)
+        }
+        openat::SimpleType::Other => {
+            anyhow::bail!("Unsupported non-file/directory {}", file_path)
+        }
+    }
+
+    Ok(())
+}
+
+// ... existing code in filesystem.rs ...
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use anyhow::Result;
+    use openat_ext::OpenatDirExt;
+    use std::fs as std_fs;
+    use std::io::Write;
+    use tempfile::tempdir;
+
+    #[test]
+    fn test_copy_single_file_basic() -> Result<()> {
+        let tmp = tempdir()?;
+        let tmp_root_dir = openat::Dir::open(tmp.path())?;
+
+        let src_root_name = "src_root";
+        let dest_root_name = "dest_root";
+
+        tmp_root_dir.create_dir(src_root_name, 0o755)?;
+        tmp_root_dir.create_dir(dest_root_name, 0o755)?;
+
+        let src_dir = tmp_root_dir.sub_dir(src_root_name)?;
+
+        let file_to_copy_rel = "file.txt";
+        let content = "This is a test file.";
+
+        // Create source file using
+        src_dir.write_file_contents(file_to_copy_rel, 0o644, content.as_bytes())?;
+
+        let src_root_abs_path_str = tmp.path().join(src_root_name).to_str().unwrap().to_string();
+        let dest_root_abs_path_str = tmp
+            .path()
+            .join(dest_root_name)
+            .to_str()
+            .unwrap()
+            .to_string();
+
+        copy_files(
+            &src_root_abs_path_str,
+            &dest_root_abs_path_str,
+            file_to_copy_rel,
+        )?;
+
+        let dest_file_abs_path = tmp.path().join(dest_root_name).join(file_to_copy_rel);
+        assert!(dest_file_abs_path.exists(), "Destination file should exist");
+        assert_eq!(
+            std_fs::read_to_string(&dest_file_abs_path)?,
+            content,
+            "File content should match"
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_copy_file_in_subdirectory() -> Result<()> {
+        let tmp = tempdir()?;
+        let tmp_root_dir = openat::Dir::open(tmp.path())?;
+
+        let src_root_name = "src";
+        let dest_root_name = "dest";
+
+        tmp_root_dir.create_dir(src_root_name, 0o755)?;
+        tmp_root_dir.create_dir(dest_root_name, 0o755)?;
+
+        let src_dir_oat = tmp_root_dir.sub_dir(src_root_name)?;
+
+        let file_to_copy_rel = "subdir/another_file.txt";
+        let content = "Content in a subdirectory.";
+
+        // Create subdirectory and file in source
+        src_dir_oat.ensure_dir_all("subdir", 0o755)?;
+        let mut f = src_dir_oat.write_file("subdir/another_file.txt", 0o644)?;
+        f.write_all(content.as_bytes())?;
+        f.flush()?;
+
+        let src_root_abs_path_str = tmp.path().join(src_root_name).to_str().unwrap().to_string();
+        let dest_root_abs_path_str = tmp
+            .path()
+            .join(dest_root_name)
+            .to_str()
+            .unwrap()
+            .to_string();
+
+        copy_files(
+            &src_root_abs_path_str,
+            &dest_root_abs_path_str,
+            file_to_copy_rel,
+        )?;
+
+        let dest_file_abs_path = tmp.path().join(dest_root_name).join(file_to_copy_rel);
+        assert!(
+            dest_file_abs_path.exists(),
+            "Destination file in subdirectory should exist"
+        );
+        assert_eq!(
+            std_fs::read_to_string(&dest_file_abs_path)?,
+            content,
+            "File content should match"
+        );
+        assert!(
+            dest_file_abs_path.parent().unwrap().is_dir(),
+            "Destination subdirectory should be a directory"
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_copy_file_with_leading_slash_in_filepath_arg() -> Result<()> {
+        let tmp = tempdir()?;
+        let tmp_root_dir = openat::Dir::open(tmp.path())?;
+
+        let src_root_name = "src";
+        let dest_root_name = "dest";
+
+        tmp_root_dir.create_dir(src_root_name, 0o755)?;
+        tmp_root_dir.create_dir(dest_root_name, 0o755)?;
+
+        let src_dir_oat = tmp_root_dir.sub_dir(src_root_name)?;
+
+        let file_rel_actual = "root_file.txt";
+        let file_arg_with_slash = "/root_file.txt";
+        let content = "Leading slash test.";
+
+        src_dir_oat.write_file_contents(file_rel_actual, 0o644, content.as_bytes())?;
+
+        let src_root_abs_path_str = tmp.path().join(src_root_name).to_str().unwrap().to_string();
+        let dest_root_abs_path_str = tmp
+            .path()
+            .join(dest_root_name)
+            .to_str()
+            .unwrap()
+            .to_string();
+
+        copy_files(
+            &src_root_abs_path_str,
+            &dest_root_abs_path_str,
+            file_arg_with_slash,
+        )?;
+
+        // The destination path should be based on the path *after* stripping the leading slash
+        let dest_file_abs_path = tmp.path().join(dest_root_name).join(file_rel_actual);
+        assert!(
+            dest_file_abs_path.exists(),
+            "Destination file should exist despite leading slash in arg"
+        );
+        assert_eq!(
+            std_fs::read_to_string(&dest_file_abs_path)?,
+            content,
+            "File content should match"
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_copy_fails_for_directory() -> Result<()> {
+        let tmp = tempdir()?;
+        let tmp_root_dir = openat::Dir::open(tmp.path())?;
+
+        let src_root_name = "src";
+        let dest_root_name = "dest";
+
+        tmp_root_dir.create_dir(src_root_name, 0o755)?;
+        tmp_root_dir.create_dir(dest_root_name, 0o755)?;
+
+        let src_dir_oat = tmp_root_dir.sub_dir(src_root_name)?;
+
+        let dir_to_copy_rel = "a_directory";
+        src_dir_oat.create_dir(dir_to_copy_rel, 0o755)?; // Create the directory in the source
+
+        let src_root_abs_path_str = tmp.path().join(src_root_name).to_str().unwrap().to_string();
+        let dest_root_abs_path_str = tmp
+            .path()
+            .join(dest_root_name)
+            .to_str()
+            .unwrap()
+            .to_string();
+
+        let result = copy_files(
+            &src_root_abs_path_str,
+            &dest_root_abs_path_str,
+            dir_to_copy_rel,
+        );
+
+        assert!(result.is_err(), "Copying a directory should fail.");
+        if let Err(e) = result {
+            let mut found_unsupported_message = false;
+            for cause in e.chain() {
+                // Iterate through the error chain
+                if cause
+                    .to_string()
+                    .contains("Unsupported copying of Directory")
+                {
+                    found_unsupported_message = true;
+                    break;
+                }
+            }
+            assert!(
+                found_unsupported_message,
+                "The error chain should contain 'Unsupported copying of Directory'. Full error: {:#?}",
+                e
+            );
+        } else {
+            panic!("Expected an error when attempting to copy a directory, but got Ok.");
+        }
+        Ok(())
+    }
+}