Add /usr/lib/rpm/macros.d/macros.rpm-ostree to set %_dbpath to /usr/share/rpm

We trigger a librpm macro file load in many of our paths. Since the
default value shipped by rpm's macro file sets `_dbpath` to
`/var/lib/rpm`, we have to explicitly set that back to `/usr/share/rpm`
in those paths.

This became more problematic recently with libsolv v0.7.17 which fully
keys off of `_dbpath` to find the rpmdb path to load:

openSUSE/libsolv@04d4d03

And it's not technically wrong; we really should make that macro not
lie. This is what this patch does by injecting an RPM macro file in our
composes which sets it to /usr/share/rpm. So then e.g. the `rpm` CLI
doesn't actually need the `/var/lib/rpm` backcompat link anymore, though
there's no harm in leaving it.

In the future, we should be able to drop this once we move all of Fedora
to `/usr/lib/sysimage/rpm` (see
coreos/fedora-coreos-tracker#639).

Closes: #2548

Author: jlebon

rust/src/composepost.rs

@@ -12,6 +12,9 @@ use std::io;
 use std::io::{BufRead, Write};
 use std::path::Path;
 
+/* See rpmostree-core.h */
+const RPMOSTREE_RPMDB_LOCATION: &'static str = "usr/share/rpm";
+
 // rpm-ostree uses /home → /var/home by default as generated by our
 // rootfs; we don't expect people to change this.  Let's be nice
 // and also fixup the $HOME entries generated by `useradd` so
@@ -55,6 +58,21 @@ fn postprocess_presets(rootfs_dfd: &openat::Dir) -> Result<()> {
     Ok(())
 }
 
+// We keep hitting issues with the ostree-remount preset not being
+// enabled; let's just do this rather than trying to propagate the
+// preset everywhere.
+fn postprocess_rpm_macro(rootfs_dfd: &openat::Dir) -> Result<()> {
+    let rpm_macros_dir = "usr/lib/rpm/macros.d";
+    rootfs_dfd.ensure_dir_all(rpm_macros_dir, 0o755)?;
+    let rpm_macros_dfd = rootfs_dfd.sub_dir(rpm_macros_dir)?;
+    rpm_macros_dfd.write_file_with("macros.rpm-ostree", 0o644, |w| -> Result<()> {
+        w.write_all(b"%_dbpath /")?;
+        w.write_all(RPMOSTREE_RPMDB_LOCATION.as_bytes())?;
+        Ok(())
+    })?;
+    Ok(())
+}
+
 // This function does two things: (1) make sure there is a /home --> /var/home substitution rule,
 // and (2) make sure there *isn't* a /var/home -> /home substition rule. The latter check won't
 // technically be needed once downstreams have:
@@ -90,6 +108,7 @@ pub(crate) fn compose_postprocess_final(rootfs_dfd: i32) -> CxxResult<()> {
         postprocess_useradd,
         postprocess_presets,
         postprocess_subs_dist,
+        postprocess_rpm_macro,
     ];
     Ok(tasks.par_iter().try_for_each(|f| f(&rootfs_dfd))?)
 }

src/libpriv/rpmostree-core.cxx

@@ -753,7 +753,8 @@ rpmostree_context_setup (RpmOstreeContext    *self,
       dnf_context_set_rpm_macro (self->dnfctx, "_install_langs", opt->str);
     }
 
-  /* This is what we use as default. */
+  /* This is what we use as default. Note we should be able to drop this in the
+   * future now that we inject a macro to set that value in our OSTrees. */
   dnf_context_set_rpm_macro (self->dnfctx, "_dbpath", "/" RPMOSTREE_RPMDB_LOCATION);
 
   /* Set the database backend only in the compose path.  It then becomes the default
@@ -4123,7 +4124,8 @@ rpmostree_context_assemble (RpmOstreeContext      *self,
   rpmtsSetRootDir (ordering_ts, dnf_context_get_install_root (dnfctx));
 
   /* First for the ordering TS, set the dbpath to relative, which will also gain
-   * the root dir.
+   * the root dir. Note we should be able to drop this in the future now that we
+   * inject a macro to set that value in our OSTrees.
    */
   set_rpm_macro_define ("_dbpath", "/" RPMOSTREE_RPMDB_LOCATION);
 

src/libpriv/rpmostree-core.h

@@ -42,6 +42,7 @@ G_BEGIN_DECLS
 #define RPMOSTREE_DIR_LOCK "lock"
 
 /* See http://lists.rpm.org/pipermail/rpm-maint/2017-October/006681.html */
+/* This is also defined on the Rust side. */
 #define RPMOSTREE_RPMDB_LOCATION "usr/share/rpm"
 #define RPMOSTREE_SYSIMAGE_DIR "usr/lib/sysimage"
 #define RPMOSTREE_SYSIMAGE_RPMDB RPMOSTREE_SYSIMAGE_DIR "/rpm"

tests/compose/libbasic-test.sh

@@ -39,6 +39,10 @@ done
 ostree --repo=${repo} ls ${treeref} /usr/lib/sysimage/rpm >/dev/null
 echo "ok db"
 
+ostree --repo=${repo} cat ${treeref} /usr/lib/rpm/macros.d/macros.rpm-ostree > rpm-ostree-macro.txt
+assert_file_has_content_literal rpm-ostree-macro.txt '%_dbpath /usr/share/rpm'
+echo "ok rpm macro"
+
 ostree --repo=${repo} show --print-metadata-key exampleos.gitrepo ${treeref} > meta.txt
 assert_file_has_content meta.txt 'rev.*97ec21c614689e533d294cdae464df607b526ab9'
 assert_file_has_content meta.txt 'src.*https://gitlab.com/exampleos/custom-atomic-host'