mkinitramfs: Create usr-merged filesystem layout

On a usr-merged filesystem /bin, /lib*, /sbin are symlinks to the
corresponding subdirectories of /usr.  When the host filesystem looks
like this, copy_file may be asked to copy both /lib/foo and
/usr/lib/foo.  It's too late at this point to make /lib a symlink
in the initramfs, and copy_file isn't general enough to do that.

Avoid this by setting up the initramfs as usr-merged.  This could
possibly cause file conflicts, but it's unlikely because:

* Policy forbids such conflicts on the host filesystem
* Few executables and libraries that go into the initramfs are
  explicitly installed in /usr on the host filesystem, because
  of historical support for having the init system mount /usr
* mkinitramfs never used to create /usr/bin or /usr/lib

Closes: #874523
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

1 files changed, 7 insertions, 1 deletions

diff --git a/mkinitramfs b/mkinitramfs
index 58a9ff7..4394a3c 100755
--- a/mkinitramfs
+++ b/mkinitramfs
@@ -215,7 +215,13 @@ export __TMPCPIOGZ
 # Private, used by 'prepend_earlyinitramfs'.
 export __TMPEARLYCPIO
 
-for d in bin conf/conf.d etc lib/modules run sbin scripts ${MODULESDIR}; do
+# Create usr-merged filesystem layout, to avoid duplicates if the host
+# filesystem is usr-merged.
+for d in /bin /lib* /sbin; do
+	mkdir -p "${DESTDIR}/usr${d}"
+	ln -s "usr${d}" "${DESTDIR}${d}"
+done
+for d in conf/conf.d etc run scripts ${MODULESDIR}; do
 	mkdir -p "${DESTDIR}/${d}"
 done