htpdate: add page (#4479)

pages/linux/htpdate.md

@@ -0,0 +1,20 @@
+# htpdate
+
+> Synchronize local date and time via HTTP headers from web servers.
+> More information: <http://www.vervest.org/htp/>.
+
+- Synchronize date and time:
+
+`sudo htpdate {{host}}`
+
+- Perform simulation of syncronization, without any action:
+
+`htpdate -q {{host}}`
+
+- Compensate the systematisch clock drift:
+
+`sudo htpdate -x {{host}}`
+
+- Set time immediate after the syncronization:
+
+`sudo htpdate -s {{host}}`