-VSWITCHD_CONF="${VSWITCHD_CONF:-/etc/ovs-vswitchd.conf}"
-VSWITCHD_PIDFILE="${VSWITCHD_PIDFILE:-/var/run/ovs-vswitchd.pid}"
-VSWITCHD_RUN_DIR="${VSWITCHD_RUN_DIR:-/var/xen/vswitch}"
-VSWITCHD_PRIORITY="${VSWITCHD_PRIORITY:--10}"
-VSWITCHD_LOGFILE="${VSWITCHD_LOGFILE:-/var/log/ovs-vswitchd.log}"
-VSWITCHD_FILE_LOGLEVEL="${VSWITCHD_FILE_LOGLEVEL:-INFO}"
-VSWITCHD_SYSLOG_LOGLEVEL="${VSWITCHD_SYSLOG_LOGLEVEL:-ERR}"
-VSWITCHD_MEMLEAK_LOGFILE="${VSWITCHD_MEMLEAK_LOGFILE:-}"
-VSWITCHD_STRACE_LOG="${VSWITCHD_STRACE_LOG:-}"
-VSWITCHD_STRACE_OPT="${VSWITCHD_STRACE_OPT:-}"
-VSWITCHD_VALGRIND_LOG="${VSWITCHD_VALGRIND_LOG:-}"
-VSWITCHD_VALGRIND_OPT="${VSWITCHD_VALGRIND_OPT:-}"
+: ${VSWITCHD_CONF:=/etc/ovs-vswitchd.conf}
+: ${VSWITCHD_PIDFILE:=/var/run/ovs-vswitchd.pid}
+: ${VSWITCHD_RUN_DIR:=/var/xen/vswitch}
+: ${VSWITCHD_PRIORITY:=-10}
+: ${VSWITCHD_LOGFILE:=/var/log/ovs-vswitchd.log}
+: ${VSWITCHD_FILE_LOGLEVEL:=INFO}
+: ${VSWITCHD_SYSLOG_LOGLEVEL:=ERR}
+: ${VSWITCHD_MEMLEAK_LOGFILE:=}
+: ${VSWITCHD_STRACE_LOG:=}
+: ${VSWITCHD_STRACE_OPT:=}
+: ${VSWITCHD_VALGRIND_LOG:=}
+: ${VSWITCHD_VALGRIND_OPT:=}