Add /etc/rpm/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 our path. (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: coreos#2548

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_dir = "usr/etc/rpm";
+    rootfs_dfd.ensure_dir_all(rpm_dir, 0o755)?;
+    let rpm_dfd = rootfs_dfd.sub_dir(rpm_dir)?;
+    rpm_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
@@ -4130,7 +4131,8 @@ 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 ${treeref} /usr/etc/rpm/macros.rpm-ostree > rpm-ostree-macro.txt
+assert_file_has_content_literal rpm-ostree-macro.txt '%_dbpath /usr/share/rpm'
+echo "ok rpm macro"
+
 ostree --repo=${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'