diff --git a/SysadminTips.page b/SysadminTips.page
index bdc9e2a..fc56e0c 100644
--- a/SysadminTips.page
+++ b/SysadminTips.page
@@ -1,3 +1,9 @@
+Edit Bind DNS serial (needs modifications, not generic).
+
+```
+sed -ri 's/^\s*[0-9]+\s*; serial/\t\t\t 2017041010\t ; serial/' db.*
+```
+
 After Debian/Ubuntu upgrade, merge local config files according to config files shipped in packages.
 
 ```