Start the pbm-agent process

Start pbm-agent on every server with the mongod node installed.

Using systemd Manually

We recommend to use the packaged service scripts to run pbm-agent.

$ sudo systemctl start pbm-agent
$ sudo systemctl status pbm-agent

You can start a pbm-agent manually. You must start a pbm-agent as the mongod user because the pbm-agent requires write access to the MongoDB data directory to make physical restores.

The following command starts the pbm-agent, redirects the output to a file and puts the process in the background:

$ su mongod nohup pbm-agent --mongodb-uri "mongodb://username:password@localhost:27018/" > /data/mdb_node_xyz/pbm-agent.$(hostname -s).27018.log 2>&1 &

Replace username and password with those of your pbm user. /data/mdb_node_xyz/ is the path where pbm-agent log files will be written. Make sure you have created this directory and granted write permissions to it for the mongod user.

Alternatively, you can run pbm-agent on a shell terminal temporarily if you want to observe and/or debug the startup from the log messages.

Multiple agents on the same host

Let’s say you run a config server (listen port 27019) on the same host as another mongod process (listen port 27018).

In this case there should be two pbm-agent processes:

• one process is connected to the mongod process (e.g. “mongodb://username:password@localhost:27018/”)
• another one - to the configsvr node (e.g. “mongodb://username:password@localhost:27019/”).

The steps below show how to achieve this:

1. Set the MongoDB connection string URI for each agent:

   $ tee /etc/sysconfig/pbm-agent1 <<EOF
   PBM_MONGODB_URI="mongodb://backupUser:backupPassword@localhost:27018/?authSource=admin"
   EOF
   

   $ tee /etc/sysconfig/pbm-agent2 <<EOF
   PBM_MONGODB_URI="mongodb://backupUser:backupPassword@localhost:27019/?authSource=admin"
   EOF
   

2. Prepare service files for each agent:

   $ tee /usr/lib/systemd/system/pbm-agent1.service <<EOF
   [Unit]
   Description=pbm-agent for mongod1
   After=time-sync.target network.target    
   
   [Service]
   EnvironmentFile=-/etc/sysconfig/pbm-agent1
   Type=simple
   User=mongod
   Group=mongod
   PermissionsStartOnly=true
   ExecStart=/usr/bin/pbm-agent    
   
   [Install]
   WantedBy=multi-user.target
   EOF
   

   $ tee /usr/lib/systemd/system/pbm-agent2.service <<EOF
   [Unit]
   Description=pbm-agent for mongod2
   After=time-sync.target network.target    
   
   [Service]
   EnvironmentFile=-/etc/sysconfig/pbm-agent2
   Type=simple
   User=mongod
   Group=mongod
   PermissionsStartOnly=true
   ExecStart=/usr/bin/pbm-agent    
   
   [Install]
   WantedBy=multi-user.target
   EOF
   

3. Reload system units and start pbm-agent processes:

   $ sudo systemctl daemon-reload
   $ sudo systemctl start pbm-agent1
   $ sudo systemctl start pbm-agent2
   

How to see the pbm-agent log

With the packaged systemd service, the log output to stdout is captured by systemd’s default redirection to systemd-journald. You can view it with the command below. See man journalctl for useful options such as --lines, --follow, etc.

$ journalctl -u pbm-agent.service
-- Logs begin at Tue 2025-01-22 09:31:34 JST. --
Jan 22 15:59:14 : Started pbm-agent.
Jan 22 15:59:14 pbm-agent[3579]: pbm agent is listening for the commands
...
...

If you started pbm-agent manually, see the file you redirected stdout and stderr to.

When a message pbm agent is listening for the commands is printed to the pbm-agent log file, pbm-agent confirms that it has connected to its mongod node successfully.

Next steps

Make a backup

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Last update: April 16, 2025
Created: April 16, 2025