Apache 用户代理在日志中为空白

Question

在 /etc/apache2/apache2.conf 中：

LogFormat "%{User-agent}i" agent

在 /etc/apache2/sites-available/default-ssl.conf 中

CustomLog ${APACHE_LOG_DIR}/access_log_agent agent

/var/log/apache2/access_log_agent 每次访问都显示一个连字符：

-
-
-

为什么我无法记录用户代理？我在 Debian 9.6 上运行 Apache 2.4.25。

Loaded Modules:
 core_module (static)
 so_module (static)
 watchdog_module (static)
 http_module (static)
 log_config_module (static)
 logio_module (static)
 version_module (static)
 unixd_module (static)
 access_compat_module (shared)
 alias_module (shared)
 auth_basic_module (shared)
 authn_core_module (shared)
 authn_file_module (shared)
 authz_core_module (shared)
 authz_host_module (shared)
 authz_user_module (shared)
 autoindex_module (shared)
 deflate_module (shared)
 dir_module (shared)
 env_module (shared)
 filter_module (shared)
 mime_module (shared)
 mpm_prefork_module (shared)
 negotiation_module (shared)
 php7_module (shared)
 reqtimeout_module (shared)
 rewrite_module (shared)
 setenvif_module (shared)
 socache_shmcb_module (shared)
 ssl_module (shared)
 status_module (shared)

Answer 1

我意外地在网络级别删除了用户代理。