feat: prune old UKI .efi files during upgrade

Containerfile.arch

@@ -168,7 +168,11 @@ RUN mkdir -p /rootfs/sysroot && \
 # grub's module files (same code path as Ubuntu; Arch has 'grub', not 'grub2').
 # ---------------------------------------------------------------------------
 FROM rootfs-common AS rootfs-grub
-RUN pacman -r /rootfs --noconfirm -Syu grub efibootmgr
+# -S --needed installs only the listed packages without a full system upgrade.
+# Avoid -Syu here: upgrading would install a newer kernel in /usr/lib/modules/
+# without a matching initramfs (dracut ran in rootfs-common for the original
+# kernel only), causing cfsctl prepare-boot to panic on the kernel-without-initramfs.
+RUN pacman -r /rootfs --noconfirm -S --needed grub efibootmgr
 RUN rm -rf /rootfs/boot/*
 
 # ---------------------------------------------------------------------------
@@ -177,7 +181,7 @@ RUN rm -rf /rootfs/boot/*
 # in rootfs-common.
 # ---------------------------------------------------------------------------
 FROM rootfs-common AS rootfs-uki
-RUN pacman -r /rootfs --noconfirm -Syu systemd-ukify
+RUN pacman -r /rootfs --noconfirm -S --needed systemd-ukify
 RUN rm -rf /rootfs/boot/*
 
 # ---------------------------------------------------------------------------
@@ -186,7 +190,7 @@ RUN rm -rf /rootfs/boot/*
 # time.  No shim needed: firmware verifies against the UEFI Signature Database.
 # ---------------------------------------------------------------------------
 FROM rootfs-common AS rootfs-uki-sb
-RUN pacman -r /rootfs --noconfirm -Syu systemd-ukify sbsigntools openssl
+RUN pacman -r /rootfs --noconfirm -S --needed systemd-ukify sbsigntools openssl
 RUN rm -rf /rootfs/boot/*
 
 # ---------------------------------------------------------------------------

src/upgrade.rs

@@ -116,6 +116,7 @@ pub fn run(reboot: bool) -> Result<()> {
         // without a writable efivarfs, e.g. container image builds).
         set_loader_conf_default(Path::new(EFI_ESP), &digest)?;
         bootctl_set_default(&digest)?;
+        prune_old_ukis(&digest)?;
     } else {
         patch_bls_entry(Path::new(BOOT_DIR), &digest, &image_ref)?;
         if !crate::install::has_grub2() {
@@ -153,6 +154,29 @@ pub fn run(reboot: bool) -> Result<()> {
     }
 }
 
+fn prune_old_ukis(new_digest: &str) -> Result<()> {
+    let running = current_composefs_digest();
+    let keep: std::collections::HashSet<&str> = std::iter::once(new_digest)
+        .chain(running.as_deref())
+        .collect();
+
+    for entry in fs::read_dir(EFI_LINUX_DIR).with_context(|| format!("reading {EFI_LINUX_DIR}"))? {
+        let entry = entry?;
+        let path = entry.path();
+        if path.extension().and_then(|e| e.to_str()) != Some("efi") {
+            continue;
+        }
+        let stem = path.file_stem().and_then(|s| s.to_str()).unwrap_or("");
+        if !keep.contains(stem) {
+            println!("Pruning old UKI: {}", path.display());
+            if let Err(e) = fs::remove_file(&path) {
+                eprintln!("warning: failed to prune {}: {e}", path.display());
+            }
+        }
+    }
+    Ok(())
+}
+
 /// Convert a Type 1 BLS entry (written by `prepare-boot` on the XBOOTLDR/`bootdir`)
 /// into a UKI .efi on the ESP (`esp`), where systemd-boot always scans.
 /// Reads the full `options` line — including the `composefs=?<hash>` token that

tests/e2e.py

@@ -439,16 +439,27 @@ def test_new_grub_entry_created(child):
     assert count >= 2, f"expected ≥2 BLS entries after upgrade, got {count}"
 
 
-def test_new_uki_entry_created(child):
-    """Two or more UKI .efi files must exist after upgrade."""
+_STALE_UKI_STEM = "0" * 64
+_STALE_UKI = f"/boot/efi/EFI/Linux/{_STALE_UKI_STEM}.efi"
+
+
+def plant_stale_uki(child):
+    """Plant a fake stale .efi (realistic hex digest stem) to give pruning something to delete."""
+    rc, _ = run_cmd(child, f"touch {_STALE_UKI}")
+    assert rc == 0, "failed to plant stale UKI"
+
+
+def test_uki_pruned(child):
+    """After upgrade: stale .efi gone, exactly 2 .efi files remain."""
+    rc, _ = run_cmd(child, f"test ! -f {_STALE_UKI}")
+    assert rc == 0, "stale UKI was not pruned after upgrade"
     rc, out = run_cmd(
         child, "echo UKICOUNT:$(ls /boot/efi/EFI/Linux/*.efi 2>/dev/null | wc -l)"
     )
     assert rc == 0, "could not count UKI entries"
     m = re.search(r"UKICOUNT:(\d+)", out)
     assert m, f"could not parse UKI count from output:\n{out!r}"
-    count = int(m.group(1))
-    assert count >= 2, f"expected ≥2 UKI entries after upgrade, got {count}"
+    assert int(m.group(1)) == 2, f"expected exactly 2 UKIs after upgrade, got {out}"
 
 
 def test_upgraded_digest_active(child, previous_digest):
@@ -541,10 +552,14 @@ def step(name, fn, *args):
         image_ref = (
             f"docker://{REGISTRY_HOST}:{registry.port}/test-image:latest"
         )
+
+        if uki:
+            step("plant_stale_uki", plant_stale_uki, child)
+
         step("switch_to_v2", test_switch, child, image_ref)
 
         if uki:
-            step("new_uki_entry_created", test_new_uki_entry_created, child)
+            step("uki_pruned", test_uki_pruned, child)
         else:
             step("new_grub_entry_created", test_new_grub_entry_created, child)