[Buildroot] [PATCH] system: add options for /bin /sbin and /lib to be symlinks into /usr

[Yann E. MORIN]

systemd is incresaingly expected things to live in /usr/bin or
/usr/sbin.

However, a lot of packages stil install stuff directly into /bin or
/sbin.

Add an option so that /bin and /sbin be symlinks to /usr/bin and
/usr/sbin. Ditto for .lib for consistency.

That option is forcibly enabled when the init system is systemd.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
---
 package/skeleton/skeleton.mk | 17 ++++++++++++++++-
 system/Config.in             | 13 +++++++++++++
 system/skeleton/bin/.empty   |  0
 system/skeleton/lib/.empty   |  0
 system/skeleton/sbin/.empty  |  0
 5 files changed, 29 insertions(+), 1 deletion(-)
 delete mode 100644 system/skeleton/bin/.empty
 delete mode 100644 system/skeleton/lib/.empty
 delete mode 100644 system/skeleton/sbin/.empty

diff --git a/package/skeleton/skeleton.mk b/package/skeleton/skeleton.mk
index 48e7085..173b485 100644
--- a/package/skeleton/skeleton.mk
+++ b/package/skeleton/skeleton.mk
@@ -19,14 +19,29 @@ else
 SKELETON_PATH = system/skeleton
 endif
 
+ifeq ($(BR2_ROOTFS_USR_SYMLINKS),y)
+define SKELETON_USR_SYMLINKS
+	ln -snf usr/bin $(TARGET_DIR)/bin
+	ln -snf usr/sbin $(TARGET_DIR)/sbin
+	ln -snf usr/lib $(TARGET_DIR)/lib
+endef
+else
+define SKELETON_NO_USR_SYMLINKS
+	$(INSTALL) -d -m 0755 $(TARGET_DIR)/bin
+	$(INSTALL) -d -m 0755 $(TARGET_DIR)/sbin
+	$(INSTALL) -d -m 0755 $(TARGET_DIR)/lib
+endef
+endif
+
 define SKELETON_INSTALL_TARGET_CMDS
 	rsync -a --ignore-times $(SYNC_VCS_EXCLUSIONS) \
 		--chmod=u=rwX,go=rX --exclude .empty --exclude '*~' \
 		$(SKELETON_PATH)/ $(TARGET_DIR)/
+	$(SKELETON_NO_USR_SYMLINKS)
+	$(SKELETON_USR_SYMLINKS)
 	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt \
 		$(TARGET_DIR_WARNING_FILE)
 	ln -snf lib $(TARGET_DIR)/$(LIB_SYMLINK)
-	mkdir -p $(TARGET_DIR)/usr
 	ln -snf lib $(TARGET_DIR)/usr/$(LIB_SYMLINK)
 endef
 
diff --git a/system/Config.in b/system/Config.in
index fad829d..96860d1 100644
--- a/system/Config.in
+++ b/system/Config.in
@@ -88,6 +88,7 @@ config BR2_INIT_SYSTEMD
 	depends on BR2_USE_MMU
 	depends on !BR2_STATIC_LIBS
 	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_10
+	select BR2_ROOTFS_USR_SYMLINKS
 	select BR2_PACKAGE_SYSTEMD
 
 comment 'systemd needs an (e)glibc toolchain, headers >= 3.10'
@@ -178,6 +179,18 @@ endif
 
 if BR2_ROOTFS_SKELETON_DEFAULT
 
+config BR2_ROOTFS_USR_SYMLINKS
+	bool "Use symlinks to /usr for /bin, /sbin and /lib"
+	help
+	  If you say 'n' here, then /bin /sbin and /lib and their
+	  counterparts in /usr will be separate directories. This
+	  is the traditional UNIX way. In this case, /usr can be a
+	  partition separate from / .
+
+	  If you say 'y' here, then /bin /sbin and /lib will be symlinks
+	  to their counterparts in /usr. This is the new systemd way. In
+	  this case, /usr has to be on the / partition.
+
 config BR2_TARGET_ENABLE_ROOT_LOGIN
 	bool "Enable root login with password"
 	default y
diff --git a/system/skeleton/bin/.empty b/system/skeleton/bin/.empty
deleted file mode 100644
index e69de29..0000000
diff --git a/system/skeleton/lib/.empty b/system/skeleton/lib/.empty
deleted file mode 100644
index e69de29..0000000
diff --git a/system/skeleton/sbin/.empty b/system/skeleton/sbin/.empty
deleted file mode 100644
index e69de29..0000000
-- 
1.9.1