lanzatool: keep unrelated files when running gc

rust/lanzatool/src/gc.rs

@@ -35,10 +35,30 @@ impl Roots {
     }
 
     pub fn collect_garbage(&self, directory: impl AsRef<Path>) -> Result<()> {
+        self.collect_garbage_with_filter(directory, |_| true)
+    }
+
+    /// Collect garbage with an additional filter.
+    ///
+    /// The filter function takes a &Path and returns a bool. The paths for which the filter
+    /// function returns true are considered for garbage collection. This means that _only_ files
+    /// that are unused AND for which the filter function returns true are deleted.
+    pub fn collect_garbage_with_filter<P>(
+        &self,
+        directory: impl AsRef<Path>,
+        mut predicate: P,
+    ) -> Result<()>
+    where
+        P: FnMut(&Path) -> bool,
+    {
         // Find all the paths not used anymore.
         let entries_not_in_use = WalkDir::new(directory.as_ref())
             .into_iter()
-            .filter(|e| !self.in_use(e.as_ref().ok()));
+            .filter(|e| !self.in_use(e.as_ref().ok()))
+            .filter(|e| match e.as_ref().ok() {
+                Some(e) => predicate(e.path()),
+                None => false,
+            });
 
         // Remove all entries not in use.
         for e in entries_not_in_use {
@@ -148,6 +168,27 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn only_delete_filtered_unused_files() -> Result<()> {
+        let tmpdir = tempfile::tempdir()?;
+        let rootdir = create_dir(tmpdir.path().join("root"))?;
+
+        let unused_file = create_file(rootdir.join("unused_file"))?;
+        let unused_file_with_prefix = create_file(rootdir.join("prefix_unused_file"))?;
+
+        let mut roots = Roots::new();
+        roots.extend(vec![&rootdir]);
+        roots.collect_garbage_with_filter(&rootdir, |p| {
+            p.file_name()
+                .and_then(|n| n.to_str())
+                .map_or(false, |n| n.starts_with("prefix_"))
+        })?;
+
+        assert!(unused_file.exists());
+        assert!(!unused_file_with_prefix.exists());
+        Ok(())
+    }
+
     fn create_file(path: PathBuf) -> Result<PathBuf> {
         fs::File::create(&path)?;
         Ok(path)

rust/lanzatool/src/install.rs

@@ -61,7 +61,20 @@ impl Installer {
         };
         self.install_links(links)?;
 
-        self.gc_roots.collect_garbage(&self.esp)?;
+        // Only collect garbage in these two directories. This way, no files that do not belong to
+        // the NixOS installation are deleted. Lanzatool takes full control over the esp/EFI/nixos
+        // directory and deletes ALL files that it doesn't know about. Dual- or multiboot setups
+        // that need files in this directory will NOT work.
+        self.gc_roots.collect_garbage(self.esp.join("EFI/nixos"))?;
+        // The esp/EFI/Linux directory is assumed to be potentially shared with other distros.
+        // Thus, only files that start with "nixos-" are garbage collected (i.e. potentially
+        // deleted).
+        self.gc_roots
+            .collect_garbage_with_filter(self.esp.join("EFI/Linux"), |p| {
+                p.file_name()
+                    .and_then(|n| n.to_str())
+                    .map_or(false, |n| n.starts_with("nixos-"))
+            })?;
 
         Ok(())
     }

rust/lanzatool/tests/gc.rs

@@ -44,6 +44,41 @@ fn keep_only_configured_number_of_generations() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn keep_unrelated_files_on_esp() -> Result<()> {
+    let esp_mountpoint = tempdir()?;
+    let tmpdir = tempdir()?;
+    let profiles = tempdir()?;
+    let generation_links: Vec<PathBuf> = [1, 2, 3]
+        .into_iter()
+        .map(|v| {
+            common::setup_generation_link(tmpdir.path(), profiles.path(), v)
+                .expect("Failed to setup generation link")
+        })
+        .collect();
+
+    // Install all 3 generations.
+    let output0 = common::lanzaboote_install(0, esp_mountpoint.path(), generation_links.clone())?;
+    assert!(output0.status.success());
+
+    let unrelated_uki = esp_mountpoint.path().join("EFI/Linux/ubuntu.efi");
+    let unrelated_os = esp_mountpoint.path().join("EFI/windows");
+    let unrelated_firmware = esp_mountpoint.path().join("dell");
+    fs::File::create(&unrelated_uki)?;
+    fs::create_dir(&unrelated_os)?;
+    fs::create_dir(&unrelated_firmware)?;
+
+    // Call `lanzatool install` again with a config limit of 2.
+    let output1 = common::lanzaboote_install(2, esp_mountpoint.path(), generation_links)?;
+    assert!(output1.status.success());
+
+    assert!(unrelated_uki.exists());
+    assert!(unrelated_os.exists());
+    assert!(unrelated_firmware.exists());
+
+    Ok(())
+}
+
 fn count_files(path: &Path) -> Result<usize> {
     Ok(fs::read_dir(path)?.count())
 }