从安全角度来看，使用htdigest比htpasswd更好，
因为htpaswd使用是的明文用户名和密码，而htdigest使用加密方法。

操作步骤：

使用用户名nagiosadmin创建htdigest密码文件

htdigest -c /etc/nagios/.htdigestpasswd "Restricted Nagios Access Zone" nagiosadmin
chmod 600 /etc/nagios/.htdigestpasswd

配置/etc/httpd/conf.d/nagios.conf文件。

编辑下面行

AuthType Digest
AuthUserFile /etc/nagios/.htdigestpasswd
AuthName "Restricted Nagios Access Zone"
require valid-user

下面是nagios.conf配置文件参考

ScriptAlias /nagios/cgi-bin/ /usr/lib64/nagios/cgi-bin/
<Directory /usr/lib64/nagios/cgi-bin/>
Options ExecCGI
order deny,allow
deny from all
allow from 127.0.0.1
AuthType Digest
AuthUserFile /etc/nagios/.htdigestpasswd
AuthName "Restricted Nagios Access Zone"
require valid-user
</Directory>
Alias /nagios/ /usr/share/nagios/html/
<Directory /usr/share/nagios/html/>
Options None
order deny,allow
deny from all
allow from 127.0.0.1
AuthType Digest
AuthUserFile /etc/nagios/.htdigestpasswd
AuthName "Restricted Nagios Access Zone"
require valid-user
</Directory>