【Linux】【RedHat8】【CentOS8】systemctl コマンド

公開日時：2019年06月30日　/　最終更新日時：2019年11月22日

RedHat 8系になって systemctl コマンドの仕様が若干変わったので、改めて systemctl コマンドの利用方法について解説します。

RedHat 6系（CentOS 6系）までは init デーモンがプロセス管理をしていましたが、RedHat 7系（CentOS 7系）からは systemd デーモンがプロセス管理をしています。

RedHat 6系（CentOS 6系）以前　←　init デーモン、chkconfig コマンド
RedHat 7系（CentOS 7系）　←　systemd デーモン、systemctl コマンド

systemd デーモンで管理されるようになることで、以前の init スクリプトはなくなり、ユニットファイル（設定ファイル）で管理されるようになりました。

サービスの確認コマンド

■サービスの確認

# systemctl -t service list-unit-files

■ユニットリストの見方

enabled　←　自動起動が有効
disabled　←　自動起動が無効
static　←　単体では自動起動しない

systemctl status コマンドでページャー（pager）機能を無効にする

RedHat 8 系になってから systemctl status コマンドを実行するとデフォルトでページャー（pager）が有効になっています。

■デフォルト

以下のようにログの最後が切れています。

[ec2-user@Test ~]$ systemctl status amazon-ssm-agent
● amazon-ssm-agent.service - amazon-ssm-agent
   Loaded: loaded (/etc/systemd/system/amazon-ssm-agent.service; enabled; vendor preset: disabled)
   Active: active (running) since Sun 2019-06-30 05:41:26 UTC; 16min ago
Main PID: 1400 (amazon-ssm-agen)
    Tasks: 8 (limit: 5003)
   Memory: 11.9M
   CGroup: /system.slice/amazon-ssm-agent.service
           mq1400 /usr/bin/amazon-ssm-agent

Jun 30 05:45:04 Test amazon-ssm-agent[1400]: 2019-06-30 05:45:04 ERROR [MessageGatewayService] Failed to ge>
Jun 30 05:46:53 Test amazon-ssm-agent[1400]: 2019-06-30 05:46:53 INFO [HealthCheck] HealthCheck reporting a>
Jun 30 05:48:49 Test amazon-ssm-agent[1400]: 2019-06-30 05:48:49 INFO [MessageGatewayService] Setting up we>
Jun 30 05:48:49 Test amazon-ssm-agent[1400]: 2019-06-30 05:48:49 ERROR [MessageGatewayService] Failed to ge>
Jun 30 05:51:29 Test amazon-ssm-agent[1400]: 2019-06-30 05:51:29 INFO [MessagingDeliveryService] [Associati>
Jun 30 05:51:53 Test amazon-ssm-agent[1400]: 2019-06-30 05:51:53 INFO [HealthCheck] HealthCheck reporting a>
Jun 30 05:56:19 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:19 INFO [MessageGatewayService] Setting up we>
Jun 30 05:56:19 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:19 ERROR [MessageGatewayService] Failed to ge>
Jun 30 05:56:26 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:26 INFO [LongRunningPluginsManager] There are>
Jun 30 05:56:53 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:53 INFO [HealthCheck] HealthCheck reporting a>
lines 1-19/19 (END)

「-l」や「--full」オプションを付けてもページャー（pager）機能によりログの最後が切れてしまいます。

[ec2-user@Test ~]$ systemctl status amazon-ssm-agent -l

● amazon-ssm-agent.service - amazon-ssm-agent
   Loaded: loaded (/etc/systemd/system/amazon-ssm-agent.service; enabled; vendor preset: disabled)
   Active: active (running) since Sun 2019-06-30 05:41:26 UTC; 19min ago
Main PID: 1400 (amazon-ssm-agen)
    Tasks: 8 (limit: 5003)
   Memory: 12.0M
   CGroup: /system.slice/amazon-ssm-agent.service
           mq1400 /usr/bin/amazon-ssm-agent

Jun 30 05:45:04 Test amazon-ssm-agent[1400]: 2019-06-30 05:45:04 ERROR [MessageGatewayService] Failed to ge>
Jun 30 05:46:53 Test amazon-ssm-agent[1400]: 2019-06-30 05:46:53 INFO [HealthCheck] HealthCheck reporting a>
Jun 30 05:48:49 Test amazon-ssm-agent[1400]: 2019-06-30 05:48:49 INFO [MessageGatewayService] Setting up we>
Jun 30 05:48:49 Test amazon-ssm-agent[1400]: 2019-06-30 05:48:49 ERROR [MessageGatewayService] Failed to ge>
Jun 30 05:51:29 Test amazon-ssm-agent[1400]: 2019-06-30 05:51:29 INFO [MessagingDeliveryService] [Associati>
Jun 30 05:51:53 Test amazon-ssm-agent[1400]: 2019-06-30 05:51:53 INFO [HealthCheck] HealthCheck reporting a>
Jun 30 05:56:19 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:19 INFO [MessageGatewayService] Setting up we>
Jun 30 05:56:19 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:19 ERROR [MessageGatewayService] Failed to ge>
Jun 30 05:56:26 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:26 INFO [LongRunningPluginsManager] There are>
Jun 30 05:56:53 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:53 INFO [HealthCheck] HealthCheck reporting a>
lines 1-19/19 (END)

「--no-pager」オプションを付けることでログを全部表示でき、且つプロンプトが返ってきます。

[ec2-user@Test ~]$ systemctl status amazon-ssm-agent -l --no-pager
● amazon-ssm-agent.service - amazon-ssm-agent
   Loaded: loaded (/etc/systemd/system/amazon-ssm-agent.service; enabled; vendor preset: disabled)
   Active: active (running) since Sun 2019-06-30 05:41:26 UTC; 21min ago
Main PID: 1400 (amazon-ssm-agen)
    Tasks: 8 (limit: 5003)
   Memory: 12.0M
   CGroup: /system.slice/amazon-ssm-agent.service
           mq1400 /usr/bin/amazon-ssm-agent

Jun 30 05:48:49 Test amazon-ssm-agent[1400]: 2019-06-30 05:48:49 INFO [MessageGatewayService] Setting up websocket for controlchannel for instance: i-09c6efd0fd52a9db4, requestId: 070ebaf4-51c3-4309-806b-25e0ecb9be35
Jun 30 05:48:49 Test amazon-ssm-agent[1400]: 2019-06-30 05:48:49 ERROR [MessageGatewayService] Failed to get controlchannel token, error: CreateControlChannel failed with error: createControlChannel request failed: unexpected response from the service <BadRequest xmlns="">Unauthorized request.
Jun 30 05:51:29 Test amazon-ssm-agent[1400]: 2019-06-30 05:51:29 INFO [MessagingDeliveryService] [Association] Schedule manager refreshed with 0 associations, 0 new associations associated
Jun 30 05:51:53 Test amazon-ssm-agent[1400]: 2019-06-30 05:51:53 INFO [HealthCheck] HealthCheck reporting agent health.
Jun 30 05:56:19 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:19 INFO [MessageGatewayService] Setting up websocket for controlchannel for instance: i-09c6efd0fd52a9db4, requestId: 6494ee8f-f553-4af9-a994-a2c82f03a9cb
Jun 30 05:56:19 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:19 ERROR [MessageGatewayService] Failed to get controlchannel token, error: CreateControlChannel failed with error: createControlChannel request failed: unexpected response from the service <BadRequest xmlns="">Unauthorized request.
Jun 30 05:56:26 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:26 INFO [LongRunningPluginsManager] There are no long running plugins currently getting executed - skipping their healthcheck
Jun 30 05:56:53 Test amazon-ssm-agent[1400]: 2019-06-30 05:56:53 INFO [HealthCheck] HealthCheck reporting agent health.
Jun 30 06:01:30 Test amazon-ssm-agent[1400]: 2019-06-30 06:01:30 INFO [MessagingDeliveryService] [Association] Schedule manager refreshed with 0 associations, 0 new associations associated
Jun 30 06:01:53 Test amazon-ssm-agent[1400]: 2019-06-30 06:01:53 INFO [HealthCheck] HealthCheck reporting agent health.
[ec2-user@Test ~]$