install/aleph: add aleph-version.json symlink

This adds a compatibility symlink along the created `.bootc-aleph.json`
named `.aleph-version.json`.

This compat symlink allow for an easier migration from osbuild's
aleph stage [1] to the aleph provided by `bootc install`.
This also create a precedent for a "standard" aleph well-known
filename that isn't tied to the name of the tool creating it.

Note that coreOS and bootupd relies on this aleph file to exist.

[1] https://github.com/osbuild/osbuild/blob/main/stages/org.osbuild.ostree.aleph

See coreos/fedora-coreos-tracker#2187

Signed-off-by: JB Trystram <jbtrystram@redhat.com>

Author: jbtrystram

crates/lib/src/install/aleph.rs

@@ -11,6 +11,8 @@ use super::SELinuxFinalState;
 
 /// Path to initially deployed version information
 pub(crate) const BOOTC_ALEPH_PATH: &str = ".bootc-aleph.json";
+/// Compatibility symlink so the aleph data is also accessible as `.aleph-version.json`
+const BOOTC_ALEPH_SYMLINK: &str = ".aleph-version.json";
 
 /// The "aleph" version information is injected into /root/.bootc-aleph.json
 /// and contains the image ID that was initially used to install.  This can
@@ -80,11 +82,15 @@ impl InstallAleph {
         Ok(r)
     }
 
-    /// Serialize to a file in the target root.
+    /// Serialize to a file in the target root, and create a compatibility symlink.
     pub(crate) fn write_to(&self, root: &Dir) -> Result<()> {
         root.atomic_replace_with(BOOTC_ALEPH_PATH, |f| {
             anyhow::Ok(self.to_canon_json_writer(f)?)
         })
-        .context("Writing aleph version")
+        .context("Writing aleph version")?;
+        // Create a symlink so the aleph data is also accessible via `.aleph-version.json`
+        root.symlink(BOOTC_ALEPH_PATH, BOOTC_ALEPH_SYMLINK)
+            .context("Creating aleph symlink")?;
+        Ok(())
     }
 }

docs/src/bootc-install.md

@@ -544,3 +544,5 @@ filesystem (`.bootc-aleph.json`) containing installation provenance information:
 
 This file is useful for auditing and understanding how a system was provisioned.
 From the booted system, this file is accessible at `/sysroot/.bootc-aleph.json`.
+A compatibility symlink `.aleph-version.json` is also created, pointing to
+`.bootc-aleph.json`.

tmt/tests/booted/readonly/013-test-aleph.nu

@@ -28,8 +28,14 @@ if $is_composefs {
 } else {
 
     let aleph_path = "/sysroot/.bootc-aleph.json"
+    let symlink_path = "/sysroot/.aleph-version.json"
     let aleph = open $aleph_path
 
+    # Verify that the compatibility symlink exists and points to the aleph file
+    assert (($symlink_path | path exists)) "aleph symlink should exist"
+    let aleph_via_symlink = open $symlink_path
+    assert equal $aleph $aleph_via_symlink "symlink content should match aleph file"
+
     # Verify required fields exist and are non-empty
     assert ($aleph.kernel | is-not-empty) "kernel field should be non-empty"
     assert ($aleph.selinux | is-not-empty) "selinux field should be non-empty"