第15章 Configuring logging by using RHEL system roles

Procedure

1. Create a playbook file, for example, ~/playbook.yml, with the following content:

   ---
   - name: Deploy the logging solution
     hosts: managed-node-01.example.com
     tasks:
       - name: Filter logs based on a specific value they contain
         ansible.builtin.include_role:
           name: redhat.rhel_system_roles.logging
         vars:
           logging_inputs:
             - name: files_input
               type: basics
           logging_outputs:
             - name: files_output0
               type: files
               property: msg
               property_op: contains
               property_value: error
               path: /var/log/errors.log
             - name: files_output1
               type: files
               property: msg
               property_op: "!contains"
               property_value: error
               path: /var/log/others.log
           logging_flows:
             - name: flow0
               inputs: [files_input]
               outputs: [files_output0, files_output1]

   The settings specified in the example playbook include the following:

   logging_inputs

   Defines a list of logging input dictionaries. The type: basics option covers inputs from systemd journal or Unix socket.

   logging_outputs

   Defines a list of logging output dictionaries. The type: files option supports storing logs in the local files, usually in the /var/log/ directory. The property: msg; property: contains; and property_value: error options specify that all logs that contain the error string are stored in the /var/log/errors.log file. The property: msg; property: !contains; and property_value: error options specify that all other logs are put in the /var/log/others.log file. You can replace the error value with the string by which you want to filter.

   logging_flows

   Defines a list of logging flow dictionaries to specify relationships between logging_inputs and logging_outputs. The inputs: [files_input] option specifies a list of inputs, from which processing of logs starts. The outputs: [files_output0, files_output1] option specifies a list of outputs, to which the logs are sent.

   For details about all variables used in the playbook and more information about rsyslog, see the /usr/share/ansible/roles/rhel-system-roles.logging/README.md file and rsyslog.conf(5) and syslog(3) manual pages on the control node.

2. Validate the playbook syntax:

   $ ansible-playbook --syntax-check ~/playbook.yml

   Note that this command only validates the syntax and does not protect against a wrong but valid configuration.

3. Run the playbook:

   $ ansible-playbook ~/playbook.yml

Verification

1. On the managed node, test the syntax of the /etc/rsyslog.conf file:

   # rsyslogd -N 1
   rsyslogd: version 8.1911.0-6.el8, config validation run...
   rsyslogd: End of config validation run. Bye.

2. On the managed node, verify that the system sends messages that contain the error string to the log:

   1. Send a test message:

      # logger error

   2. View the /var/log/errors.log log, for example:

      # cat /var/log/errors.log
      Aug  5 13:48:31 hostname root[6778]: error

      Where hostname is the host name of the client system. Note that the log contains the user name of the user that entered the logger command, in this case root.