As already discussed the OPS Manager is centralized based manager for Mongo. Ergo it has server and agent. Agent should be also running on the OPS Manager server, so let's check how stop start an agent:

We can check the status of the manager as follows (on the manager machine of course)

[root@dbpafxjrl ~]# service mongodb-mms status
Check Ops Manager status
   Probing instance 0...[  OK  ]
      The instance is running.
Check Backup Daemon status[  OK  ]
   Backup Daemon Process is running.
[root@dbpafxjrl ~]#

We can also start it as follows:

[root@dbpafxjrl ~]# service mongodb-mms start
Starting pre-flight checks
Successfully finished pre-flight checks

Migrate Ops Manager data
   Running migrations...[OK]
Start Ops Manager server
   Instance 0 starting............[OK]
Starting pre-flight checks
Successfully finished pre-flight checks

Starting Backup Deamon....[OK]
.........................
[root@dbpafxjrl ~]#

Agent is installed on the server and the destination hosts and should be running everywhere. So let's see how to check it's status and how to stop start it:

[root@dbpafxjrl ~]# systemctl status mongodb-mms-automation-agent.service
● mongodb-mms-automation-agent.service - MongoDB MMS Automation Agent
   Loaded: loaded (/etc/systemd/system/mongodb-mms-automation-agent.service; disabled; vendor preset: disabled)
   Active: inactive (dead)

[root@dbpafxjrl ~]# systemctl start mongodb-mms-automation-agent.service
[root@dbpafxjrl ~]# systemctl status mongodb-mms-automation-agent.service
● mongodb-mms-automation-agent.service - MongoDB MMS Automation Agent
   Loaded: loaded (/etc/systemd/system/mongodb-mms-automation-agent.service; disabled; vendor preset: disabled)
   Active: active (running) since Mon 2020-03-23 11:10:18 CET; 1s ago
  Process: 21831 ExecStartPre=/usr/bin/chown -R mongod:mongod /var/run/mongodb-mms-automation (code=exited, status=0/SUCCESS)
  Process: 21829 ExecStartPre=/usr/bin/mkdir /var/run/mongodb-mms-automation (code=exited, status=0/SUCCESS)
 Main PID: 21834 (mongodb-mms-aut)
   CGroup: /system.slice/mongodb-mms-automation-agent.service
           ├─21834 /opt/mongodb-mms-automation/bin/mongodb-mms-automation-agent -f /etc/mongodb-mms/automation-agent.config -pidfilepath /var/run/mongodb-mms-automation/mongodb-mms-automation-agent.pid >> /var/log/mongodb-mms-automati...
           ├─21936 /var/lib/mongodb-mms-automation/mongodb-linux-x86_64-4.0.6-ent/bin/mongod -f /data/db_backup/automation-mongod.conf
           ├─21937 /var/lib/mongodb-mms-automation/mongodb-linux-x86_64-4.0.6-ent/bin/mongod -f /data/db_backup/automation-mongod.conf
           ├─21938 /var/lib/mongodb-mms-automation/mongodb-linux-x86_64-4.0.6-ent/bin/mongod -f /data/db_backup/automation-mongod.conf
           ├─21944 /var/lib/mongodb-mms-automation/mongodb-mms-monitoring-agent-6.6.2.466-1.rhel7_x86_64/mongodb-mms-monitoring-agent
           └─21947 /var/lib/mongodb-mms-automation/mongodb-mms-backup-agent-6.8.6.1018-1.rhel7_x86_64/mongodb-mms-backup-agent

Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: authorization: enabled
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: keyFile: /var/lib/mongodb-mms-automation/keyfile
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: setParameter:
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: authenticationMechanisms: SCRAM-SHA-1,SCRAM-SHA-256
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: storage:
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: dbPath: /data/db_backup
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: engine: wiredTiger
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: systemLog:
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: destination: file
Mar 23 11:10:18 dbpafxjrl mongodb-mms-automation-agent[21834]: path: /data/db_backup/log/mongod.log