Apacheのエラー[httpd: Could not reliably determine the server’s fully qualified domain name]を対策する方法

Apacheの起動時や、「apachectl -V」でApacheの状態を確認した際に、
「httpd: Could not reliably determine the server’s fully qualified domain name ～以下略…」
というエラーが出るときがある。

そんなときの対策方法です。

※動作確認環境
CentOS 7.6
Apache 2.4.6

原因

Apacheの設定ファイル「httpd.conf」にて「ServerName」が設定されていない時にこのエラーが表示されます。

# apachectl -V
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using www.example.net. Set the 'ServerName' directive globally to suppress this message
Server version: Apache/2.4.6 (CentOS)
Server built:   Jul 10 2018 13:31:35
Server's Module Magic Number: 20120211:24
Server loaded:  APR 1.4.8, APR-UTIL 1.5.2
Compiled using: APR 1.4.8, APR-UTIL 1.5.2
Architecture:   64-bit
Server MPM:     prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_SYSVSEM_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=256
 -D HTTPD_ROOT="/etc/httpd"
 -D SUEXEC_BIN="/usr/sbin/suexec"
 -D DEFAULT_PIDLOG="/run/httpd/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="conf/mime.types"
 -D SERVER_CONFIG_FILE="conf/httpd.conf"

# apachectl -V

AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using www.example.net. Set the 'ServerName' directive globally to suppress this message

Server version: Apache/2.4.6 (CentOS)

Server built: Jul 10 2018 13:31:35

Server's Module Magic Number: 20120211:24

Server loaded: APR 1.4.8, APR-UTIL 1.5.2

Compiled using: APR 1.4.8, APR-UTIL 1.5.2

Architecture: 64-bit

Server MPM: prefork

threaded: no

forked: yes (variable process count)

Server compiled with....

-D APR_HAS_SENDFILE

-D APR_HAS_MMAP

-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)

-D APR_USE_SYSVSEM_SERIALIZE

-D APR_USE_PTHREAD_SERIALIZE

-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT

-D APR_HAS_OTHER_CHILD

-D AP_HAVE_RELIABLE_PIPED_LOGS

-D DYNAMIC_MODULE_LIMIT=256

-D HTTPD_ROOT="/etc/httpd"

-D SUEXEC_BIN="/usr/sbin/suexec"

-D DEFAULT_PIDLOG="/run/httpd/httpd.pid"

-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"

-D DEFAULT_ERRORLOG="logs/error_log"

-D AP_TYPES_CONFIG_FILE="conf/mime.types"

-D SERVER_CONFIG_FILE="conf/httpd.conf"

対策

vi等でApacheの設定ファイル「httpd.conf」を開きます。

# vi /etc/httpd/conf/httpd.conf

1	# vi /etc/httpd/conf/httpd.conf

# ServerName gives the name and port that the server uses to identify itself.
# This can often be determined automatically, but we recommend you specify
# it explicitly to prevent problems during startup.
#
# If your host doesn't have a registered DNS name, enter its IP address here.
#
#ServerName www.example.com:80

# ServerName gives the name and port that the server uses to identify itself.

# This can often be determined automatically, but we recommend you specify

# it explicitly to prevent problems during startup.

# If your host doesn't have a registered DNS name, enter its IP address here.

#ServerName www.example.com:80

「#ServerName www.example.com:80」という行のコメントを消して、現在利用中のドメイン（又はホスト名）を記入して保存します。

バーチャルホストで複数のサイトを公開している場合や、ローカル環境でのApacheの場合は、「ServerName localhost:80」と記入しましょう。

ServerName www.example.net:80

1	ServerName www.example.net:80

Apacheを再起動します。

# systemctl restart httpd

1	# systemctl restart httpd

エラーが消えたか「apachectl -V」で確認します。

# apachectl -V
Server version: Apache/2.4.6 (CentOS)
Server built:   Jul 10 2018 13:31:35
Server's Module Magic Number: 20120211:24
Server loaded:  APR 1.4.8, APR-UTIL 1.5.2
Compiled using: APR 1.4.8, APR-UTIL 1.5.2
Architecture:   64-bit
Server MPM:     prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_SYSVSEM_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=256
 -D HTTPD_ROOT="/etc/httpd"
 -D SUEXEC_BIN="/usr/sbin/suexec"
 -D DEFAULT_PIDLOG="/run/httpd/httpd.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="conf/mime.types"
 -D SERVER_CONFIG_FILE="conf/httpd.conf"