diff --git a/doc/build.md b/doc/build.md
index df2a427..e93fe60 100644
--- a/doc/build.md
+++ b/doc/build.md
@@ -101,7 +101,9 @@ As an administrator (or root):
 ```
 yum update
 
-# Firewall is OK by default??
+sudo systemctl enable firewalld
+sudo systemctl start firewalld
+sudo firewall-cmd --list-all
 
 # Check for SSH password logins; they should be disabled
 grep '^[^#]*PasswordAuthentication' /etc/ssh/sshd_config
--
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