udhcpc: support resolv.conf symlinks

Often it is desirable to have /etc/ be on read-only storage (well, the whole rootfs) but have things like /etc/resolv.conf be symlinks to a writable location. Tweak the simple script to support that. Signed-off-by: Mike Frysinger <[email protected]>
SocalDom · Feb 27, 2013 · 39b8fb4 · 39b8fb4
1 parent 40b97fb
commit 39b8fb4
Showing 1 changed file with 8 additions and 4 deletions.
diff --git a/examples/udhcp/simple.script b/examples/udhcp/simple.script
@@ -34,13 +34,17 @@ case "$1" in
 		fi
 
 		echo "Recreating $RESOLV_CONF"
-		echo -n > $RESOLV_CONF-$$
-		[ -n "$domain" ] && echo "search $domain" >> $RESOLV_CONF-$$
+		# If the file is a symlink somewhere (like /etc/resolv.conf
+		# pointing to /run/resolv.conf), make sure things work.
+		realconf=$(realpath "$RESOLV_CONF" 2>/dev/null || echo "$RESOLV_CONF")
+		tmpfile="$realconf-$$"
+		> "$tmpfile"
+		[ -n "$domain" ] && echo "search $domain" >> "$tmpfile"
 		for i in $dns ; do
 			echo " Adding DNS server $i"
-			echo "nameserver $i" >> $RESOLV_CONF-$$
+			echo "nameserver $i" >> "$tmpfile"
 		done
-		mv $RESOLV_CONF-$$ $RESOLV_CONF
+		mv "$tmpfile" "$realconf"
 		;;
 esac