dockerd: add docker-storage to init

Docker's backend storage driver can be configurable for certain
filesystems. The default is the overlay storage driver, but if you run
openwrt on a system with btrfs, this will allow you to override the
default configuration by settings the storage_driver in uci in dockerd's
global section. This value will be used in the created dockerd.json
file.

Signed-off-by: Keith T. Garner <kgarner@kgarner.com>

utils/dockerd/Makefile

@@ -2,7 +2,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=dockerd
 PKG_VERSION:=27.3.1
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 PKG_LICENSE:=Apache-2.0
 PKG_LICENSE_FILES:=LICENSE
 

utils/dockerd/files/dockerd.init

@@ -189,6 +189,7 @@ process_config() {
 	config_get http_proxy proxies http_proxy "${http_proxy}"
 	config_get https_proxy proxies https_proxy "${https_proxy}"
 	config_get no_proxy proxies no_proxy "${no_proxy}"
+	config_get storage_driver globals storage_driver ""
 
 	. /usr/share/libubox/jshn.sh
 	json_init
@@ -218,6 +219,7 @@ process_config() {
 		[ -z "${no_proxy}" ] || json_add_string "no-proxy" "${no_proxy}"
 		json_close_object
 	fi
+	[ -z "${storage_driver}" ] || json_add_string "storage-driver" "${storage_driver}"
 	json_dump > "${DOCKERD_CONF}"
 
 	[ "${iptables}" -eq "1" ] && config_foreach iptables_add_blocking_rule firewall