composefs: Generate both V1 and V2 EROFS images on install

composefs-rs landed support for V1 EROFS, which we need
to enable composefs on RHEL9.

Make new installs produce both V1 and V2 EROFS images for committed
composefs images so a deployment can be booted via either the
composefs= (V2) or composefs.digest.v1= (V1) karg.

Karg generation and digest computation default to V2 for now;
this change only ensures both digests are available on disk.

Assisted-by: OpenCode (Claude Sonnet 4.6)
Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

crates/initramfs/src/lib.rs

@@ -464,7 +464,7 @@ pub fn setup_root(args: Args) -> Result<()> {
     };
 
     let composefs = ComposefsCmdline::<Sha512HashValue>::from_cmdline(&cmdline)?
-        .context("No composefs= or composefs.digest.v1= karg found")?;
+        .context("No composefs= or composefs.digest= karg found")?;
     let image = composefs.digest();
     let insecure = composefs.is_insecure();
 

crates/lib/src/bootc_composefs/boot.rs

@@ -785,6 +785,12 @@ struct UKIInfo {
     version: Option<String>,
     os_id: Option<String>,
     boot_digest: String,
+    /// The composefs image digest parsed from (and validated against) the UKI's
+    /// own cmdline.  This is the authoritative deployment key for UKI boots:
+    /// setup-root opens `state/deploy/<this>` using the karg baked into the UKI,
+    /// so the deploy directory must be named after exactly this value regardless
+    /// of which EROFS format (V1 or V2) was sealed.
+    composefs_cmdline: Sha512HashValue,
 }
 
 /// Writes a PortableExecutable to ESP along with any PE specific or Global addons
@@ -795,6 +801,7 @@ fn write_pe_to_esp(
     file_path: &Utf8Path,
     pe_type: PEType,
     uki_id: &Sha512HashValue,
+    boot_ids: &[&Sha512HashValue],
     missing_fsverity_allowed: bool,
     mounted_efi: impl AsRef<Path>,
 ) -> Result<Option<UKIInfo>> {
@@ -815,7 +822,7 @@ fn write_pe_to_esp(
 
         let parsed_cmdline = BootComposefsCmdline::<Sha512HashValue>::from_cmdline(&cmdline)
             .context("Parsing composefs=")?
-            .context("No composefs= or composefs.digest.v1= karg found in UKI cmdline")?;
+            .context("No composefs= or composefs.digest= karg found in UKI cmdline")?;
         let composefs_cmdline = parsed_cmdline.digest().clone();
         let missing_verity_allowed_cmdline = parsed_cmdline.is_insecure();
 
@@ -835,11 +842,9 @@ fn write_pe_to_esp(
             _ => { /* no-op */ }
         }
 
-        if composefs_cmdline != *uki_id {
-            anyhow::bail!(
-                "The UKI has the wrong composefs= parameter (is '{composefs_cmdline:?}', should be {uki_id:?})"
-            );
-        }
+        parsed_cmdline
+            .validate_digest(boot_ids.iter().copied())
+            .context("Validating UKI composefs digest")?;
 
         uki_reader.seek(SeekFrom::Start(0))?;
         let osrel = uki::get_text_section_buffered(&mut uki_reader, ".osrel")?;
@@ -856,6 +861,7 @@ fn write_pe_to_esp(
             version: parsed_osrel.get_version(),
             os_id: parsed_osrel.get_value(&["ID"]),
             boot_digest,
+            composefs_cmdline,
         });
     }
 
@@ -1071,8 +1077,9 @@ pub(crate) fn setup_composefs_uki_boot(
     setup_type: BootSetupType,
     repo: crate::store::ComposefsRepository,
     id: &Sha512HashValue,
+    boot_ids: &[&Sha512HashValue],
     entries: Vec<ComposefsBootEntry<Sha512HashValue>>,
-) -> Result<String> {
+) -> Result<(String, Sha512HashValue)> {
     let (root_path, esp_device, bootloader, missing_fsverity_allowed, uki_addons) = match setup_type
     {
         BootSetupType::Setup((root_setup, state, postfetch)) => {
@@ -1152,7 +1159,8 @@ pub(crate) fn setup_composefs_uki_boot(
                     &entry.file,
                     utf8_file_path,
                     entry.pe_type,
-                    &id,
+                    id,
+                    boot_ids,
                     missing_fsverity_allowed,
                     esp_mount.dir.path(),
                 )?;
@@ -1169,6 +1177,13 @@ pub(crate) fn setup_composefs_uki_boot(
 
     let boot_digest = uki_info.boot_digest.clone();
 
+    // The deploy key for a UKI boot is the composefs digest baked into the UKI
+    // cmdline (already validated against `boot_ids` in `write_pe_to_esp`).
+    // setup-root opens `state/deploy/<this>` using that same karg, so we must
+    // key the deployment off exactly this value -- whether the UKI was sealed
+    // with the V2 (default) or V1 EROFS digest.
+    let deploy_id = uki_info.composefs_cmdline.clone();
+
     match bootloader {
         Bootloader::Grub => {
             write_grub_uki_menuentry(root_path, &setup_type, uki_info.boot_label, id, &esp_device)?
@@ -1179,7 +1194,7 @@ pub(crate) fn setup_composefs_uki_boot(
         Bootloader::None => unreachable!("Checked at install time"),
     };
 
-    Ok(boot_digest)
+    Ok((boot_digest, deploy_id))
 }
 
 /// A composefs image attached to a temporary directory with the ESP and a
@@ -1350,6 +1365,15 @@ pub(crate) async fn setup_composefs_boot(
     let id = composefs_oci::generate_boot_image(&repo, &pull_result.manifest_digest)
         .context("Generating bootable EROFS image")?;
 
+    // Open the OCI image to read both stored boot EROFS digests.  The UKI may
+    // have been sealed with either the V1 or V2 boot image digest, so we need
+    // both for verification.
+    let oci_img =
+        composefs_oci::oci_image::OciImage::open(&*repo, &pull_result.manifest_digest, None)
+            .context("Opening OCI image to read boot image refs")?;
+    let boot_id_v1 = oci_img.boot_image_ref_v1().cloned();
+    let boot_id_v2 = oci_img.boot_image_ref_v2().cloned();
+
     // Reconstruct the OCI filesystem to discover boot entries (kernel, initramfs, etc.).
     let fs = composefs_oci::image::create_filesystem(&*repo, &pull_result.config_digest, None)
         .context("Creating composefs filesystem for boot entry discovery")?;
@@ -1402,25 +1426,49 @@ pub(crate) async fn setup_composefs_boot(
         )
     })?;
 
-    let boot_digest = match boot_type {
-        BootType::Bls => setup_composefs_bls_boot(
-            BootSetupType::Setup((&root_setup, &state, &postfetch)),
-            repo,
-            &id,
-            entry,
-            mounted_root.dir(),
-        )?,
+    // The deployment key is the hash that setup-root looks for in
+    // state/deploy/<hash>, derived from the composefs karg.  The two boot types
+    // establish that karg differently:
+    //
+    //  * BLS: bootc writes the karg itself, so we are free to choose the key.
+    //    Prefer the V2 digest (matching the default EROFS format), falling back
+    //    to the primary id for legacy repos with no separate V2 boot ref.
+    //
+    //  * UKI: the karg is baked into the UKI at seal time, so the key is
+    //    whatever digest the UKI carries.  `setup_composefs_uki_boot` parses and
+    //    validates that against the boot refs and returns it, so we override the
+    //    provisional value below.  This keeps us correct whether the UKI was
+    //    sealed with the V2 (default) or V1 EROFS digest.
+    let provisional_deploy_id = boot_id_v2.as_ref().cloned().unwrap_or_else(|| id.clone());
+
+    // Collect whichever boot image refs exist; the UKI cmdline may carry either.
+    let boot_ids_owned: Vec<Sha512HashValue> =
+        [boot_id_v1, boot_id_v2].into_iter().flatten().collect();
+    let boot_ids: Vec<&Sha512HashValue> = boot_ids_owned.iter().collect();
+
+    let (boot_digest, deploy_id) = match boot_type {
+        BootType::Bls => (
+            setup_composefs_bls_boot(
+                BootSetupType::Setup((&root_setup, &state, &postfetch)),
+                repo,
+                &provisional_deploy_id,
+                entry,
+                mounted_root.dir(),
+            )?,
+            provisional_deploy_id,
+        ),
         BootType::Uki => setup_composefs_uki_boot(
             BootSetupType::Setup((&root_setup, &state, &postfetch)),
             repo,
-            &id,
+            &provisional_deploy_id,
+            &boot_ids,
             entries,
         )?,
     };
 
     write_composefs_state(
         &root_setup.physical_root_path,
-        &id,
+        &deploy_id,
         &crate::spec::ImageReference::from(state.target_imgref.clone()),
         None,
         boot_type,

crates/lib/src/bootc_composefs/digest.rs

@@ -23,8 +23,8 @@ use crate::store::ComposefsRepository;
 /// Creates a temporary composefs repository for computing digests.
 ///
 /// The `erofs_version` controls which EROFS format the digest is computed for:
-/// use `FormatVersion::V1` to get a `composefs.digest.v1=` karg (V1 EROFS, C-tool
-/// compatible) or `FormatVersion::V2` for the legacy `composefs=` karg.
+/// use `FormatVersion::V1` to get a `composefs.digest=v1-sha256-12:<hex>` karg (V1 EROFS,
+/// C-tool compatible) or `FormatVersion::V2` for the legacy `composefs=<hex>` karg.
 ///
 /// Returns the TempDir guard (must be kept alive for the repo to remain valid)
 /// and the repository wrapped in Arc.

crates/lib/src/bootc_composefs/gc.rs

@@ -402,16 +402,20 @@ pub(crate) async fn composefs_gc(
                         ref_digest,
                         None,
                     ) {
-                        if let Some(img_ref) = img.image_ref() {
-                            if img_ref.to_hex() == *verity {
-                                tracing::info!(
-                                    "Deployment {verity} has no manifest_digest in origin; \
-                                     found matching manifest {ref_digest} via image_ref"
-                                );
-                                live_manifest_digests.push(ref_digest.clone());
-                                found_manifest = true;
-                                break;
-                            }
+                        // Check both V1 and V2 slots: the deployment verity
+                        // may have been produced under either format.
+                        let img_ref_hex = img
+                            .image_ref_v1()
+                            .or_else(|| img.image_ref_v2())
+                            .map(|id| id.to_hex());
+                        if img_ref_hex.as_deref() == Some(verity.as_str()) {
+                            tracing::info!(
+                                "Deployment {verity} has no manifest_digest in origin; \
+                                 found matching manifest {ref_digest} via image_ref"
+                            );
+                            live_manifest_digests.push(ref_digest.clone());
+                            found_manifest = true;
+                            break;
                         }
                     }
                 }

crates/lib/src/bootc_composefs/repo.rs

@@ -99,7 +99,7 @@ pub(crate) async fn initialize_composefs_repository(
 
     crate::store::ensure_composefs_dir(rootfs_dir)?;
 
-    let config = {
+    let mut config = {
         let c =
             composefs::repository::RepositoryConfig::new(composefs::fsverity::Algorithm::SHA512);
         if allow_missing_fsverity {
@@ -108,6 +108,13 @@ pub(crate) async fn initialize_composefs_repository(
             c
         }
     };
+    // Generate both V1 and V2 EROFS images so a deployment can be booted via
+    // either the composefs= legacy shorthand (V2) or composefs.digest= (V1/V2)
+    // karg.  This makes both digests available for any boot path.
+    config.erofs_formats = composefs::erofs::format::FormatConfig {
+        default: composefs::erofs::format::FormatVersion::V1,
+        extra: [composefs::erofs::format::FormatVersion::V2].into(),
+    };
     let (repo, _created) =
         crate::store::ComposefsRepository::init_path(rootfs_dir, "composefs", config)
             .context("Failed to initialize composefs repository")?;