[PATCH] base-files: add option to make /var persistent

[Stijn Tintel]

In OpenWrt, /var is symlinked to /tmp by default. This is done to reduce
the amount of writes to the flash chip, which often don't have the
greatest durability. As a result, things like DHCP or UPnP lease files,
are not persistent across reboots.

Since OpenWrt can run on devices with more durable storage, it makes
sense to have an option for a persistent /var. Add an option to make
/var persistent. When enabled, /var will no longer be symlinked to /tmp,
but /var/run will be symlink to /tmp/run, as it should contain only
files that should not be kept during reboot. The option is off by
default, to maintain the current behaviour.

Signed-off-by: Stijn Tintel <stijn at linux-ipv6.be>
---
 config/Config-images.in     | 6 ++++++
 package/base-files/Makefile | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/config/Config-images.in b/config/Config-images.in
index 4a7f08824b..dc68fade3c 100644
--- a/config/Config-images.in
+++ b/config/Config-images.in
@@ -303,4 +303,10 @@ menu "Target Images"
 		  it will be mounted by PARTUUID which makes the kernel find the
 		  appropriate disk automatically.
 
+	config TARGET_ROOTFS_PERSIST_VAR
+		bool "Make /var persistent"
+		default n
+		help
+		  Do not symlink /var to /tmp, so that its content will
+		  persist across reboots.
 endmenu
diff --git a/package/base-files/Makefile b/package/base-files/Makefile
index 5f816a0d1b..687fbc5f78 100644
--- a/package/base-files/Makefile
+++ b/package/base-files/Makefile
@@ -172,8 +172,13 @@ define Package/base-files/install
 	mkdir -p $(1)/www
 	mkdir -p $(1)/root
 	$(LN) /proc/mounts $(1)/etc/mtab
+ifeq ($(CONFIG_TARGET_ROOTFS_PERSIST_VAR),n)
 	rm -f $(1)/var
 	$(LN) tmp $(1)/var
+else
+	mkdir $(1)/var
+	$(LN) /tmp/run $(1)/var/run
+endif
 	mkdir -p $(1)/etc
 	$(LN) /tmp/resolv.conf /tmp/TZ /tmp/localtime $(1)/etc/
 
-- 
2.31.1