LogFormatを書き換え用と思ったら「Note that the use of %{X-Forwarded-For}i instead of %h is not recommended.」でubuntoでmod_remoteip

ConohaVPSではアクセスIPはWAFのIPになります。
%{X-Forwarded-For}iを設定しようとしたら、注意文になにやらmod_remoteipを使えと。。

These deviate from the Common Log Format definitions in that they use %O
(the actual bytes sent including headers) instead of %b (the size of the requested file), because the latter makes it impossible to detect partial
requests.

#Note that the use of %{X-Forwarded-For}i instead of %h is not recommended.
#Use mod_remoteip instead.
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %O" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent

知らなかった。
昔から%{X-Forwarded-For}iを追加を何も考えずに設定していたので初めてmod_remoteipを設定してみる。

root@conoha-dev:~#apachectl configtest
AH00526: Syntax error on line 227 of /etc/apache2/apache2.conf:
Invalid command 'RemoteIPHeader', perhaps misspelled or defined by a module not included in the server configuration
Action 'configtest' failed.
The Apache error log may have more information.
root@conoha-dev:~#

あれ？モジュールがない？
a2enmodでモジュールをロードします。

root@conoha-dev:/etc/apache2# a2enmod remoteip
Enabling module remoteip.
To activate the new configuration, you need to run:
  systemctl restart apache2
root@conoha-dev:/etc/apache2# tree
├── mods-enabled
│   ├── access_compat.load -> ../mods-available/access_compat.load
│   ├── alias.conf -> ../mods-available/alias.conf
│   ├── alias.load -> ../mods-available/alias.load
│   ├── auth_basic.load -> ../mods-available/auth_basic.load
│   ├── authn_core.load -> ../mods-available/authn_core.load
│   ├── authn_file.load -> ../mods-available/authn_file.load
│   ├── authz_core.load -> ../mods-available/authz_core.load
│   ├── authz_host.load -> ../mods-available/authz_host.load
│   ├── authz_user.load -> ../mods-available/authz_user.load
│   ├── autoindex.conf -> ../mods-available/autoindex.conf
│   ├── autoindex.load -> ../mods-available/autoindex.load
│   ├── deflate.conf -> ../mods-available/deflate.conf
│   ├── deflate.load -> ../mods-available/deflate.load
│   ├── dir.conf -> ../mods-available/dir.conf
│   ├── dir.load -> ../mods-available/dir.load
│   ├── env.load -> ../mods-available/env.load
│   ├── filter.load -> ../mods-available/filter.load
│   ├── mime.conf -> ../mods-available/mime.conf
│   ├── mime.load -> ../mods-available/mime.load
│   ├── mpm_prefork.conf -> ../mods-available/mpm_prefork.conf
│   ├── mpm_prefork.load -> ../mods-available/mpm_prefork.load
│   ├── negotiation.conf -> ../mods-available/negotiation.conf
│   ├── negotiation.load -> ../mods-available/negotiation.load
│   ├── php7.2.conf -> ../mods-available/php7.2.conf
│   ├── php7.2.load -> ../mods-available/php7.2.load
│   ├── reqtimeout.conf -> ../mods-available/reqtimeout.conf
│   ├── reqtimeout.load -> ../mods-available/reqtimeout.load
│   ├── rewrite.load -> ../mods-available/rewrite.load
│   ├── setenvif.conf -> ../mods-available/setenvif.conf
│   ├── setenvif.load -> ../mods-available/setenvif.load
│   ├── socache_shmcb.load -> ../mods-available/socache_shmcb.load
│   ├── ssl.conf -> ../mods-available/ssl.conf
│   ├── ssl.load -> ../mods-available/ssl.load
│   ├── status.conf -> ../mods-available/status.conf
│   └── status.load -> ../mods-available/status.load
├── ports.conf

root@conoha-dev:/etc/apache2#apachectl configtest
Syntax OK
root@conoha-dev:/etc/apache2#