RHEL 8 New Features for Experienced Linux Administrators

Log in to your workstation host as student. Verify that ansible is available, and change to the tools-automating working directory.

1. Verify that ansible is available.

   [student@workstation ~]$ yum list installed ansible
   ...output omitted...

2. Change to the tools-automating working directory.

   [student@workstation ~]$ cd ~/tools-automating
   [student@workstation tools-automating]$ 

Install the RHEL system roles on the control node, workstation.lab.example.com. Verify the location of the installed roles on the control node.

1. Use ansible-galaxy to verify that no roles are initially available. The empty output indicates that no roles were found.

   [student@workstation tools-automating]$ ansible-galaxy list
   ...output omitted...
   [student@workstation tools-automating]$ 

2. Install the rhel-system-roles package.

   [student@workstation tools-automating]$ sudo yum install rhel-system-roles
   ...output omitted...
   Is this ok [y/N]: y
   ...output omitted...

3. Use ansible-galaxy to verify that system roles are available.

   [student@workstation tools-automating]$ ansible-galaxy list
   - linux-system-roles.kdump, (unknown version)
   - linux-system-roles.network, (unknown version)
   - linux-system-roles.postfix, (unknown version)
   - linux-system-roles.selinux, (unknown version)
   - linux-system-roles.timesync, (unknown version)
   - rhel-system-roles.kdump, (unknown version)
   - rhel-system-roles.network, (unknown version)
   - rhel-system-roles.postfix, (unknown version)
   - rhel-system-roles.selinux, (unknown version)
   - rhel-system-roles.timesync, (unknown version)

   Roles are located in the /usr/share/ansible/roles directory. A role beginning with linux-system-roles is a symlink to the matching rhel-system-roles role.

Create a playbook, configure_time.yml, with one play that targets the database_servers host group. Include the rhel-system-roles.timesync role in the roles section of the play.

The contents of the configure_time.yml now matches:

---
- name: Time Synchronization
  hosts: database_servers

  roles:
    - rhel-system-roles.timesync

The role documentation contains a description of each role variable, including its default value. Determine the role variables to override to meet the time synchronization requirements.

Place role variable values in a file named timesync.yml. Because these variable values apply to all inventory hosts, place the file in the group_vars/all subdirectory.

1. Review the Role Variables section of the README.md file for the rhel-system-roles.timesync role.

   [student@workstation tools-automating]$ cat \
   > /usr/share/doc/rhel-system-roles/timesync/README.md
   ...output omitted...
   Role Variables
   --------------
   
   ...output omitted...
   # List of NTP servers
   timesync_ntp_servers:
     - hostname: foo.example.com   # Hostname or address of the server
       minpoll: 4                  # Minimum polling interval (default 6)
       maxpoll: 8                  # Maximum polling interval (default 10)
       iburst: yes                 # Flag enabling fast initial synchronization
                                   # (default no)
       pool: no                    # Flag indicating that each resolved address
                                   # of the hostname is a separate NTP server
                                   # (default no)
   ...output omitted...
   # Name of the package which should be installed and configured for NTP.
   # Possible values are "chrony" and "ntp". If not defined, the currently active
   # or enabled service will be configured. If no service is active or enabled, a
   # package specific to the system and its version will be selected.
   timesync_ntp_provider: chrony

2. Create the group_vars/all subdirectory.

   [student@workstation tools-automating]$ mkdir -pv group_vars/all
   mkdir: created directory 'group_vars'
   mkdir: created directory 'group_vars/all'
   

3. Create a new file group_vars/all/timesync.yml using a text editor. Add variable definitions to satisfy the time synchronization requirements. The file now contains:

   ---
   #rhel-system-roles.timesync variables for all hosts
   
   timesync_ntp_provider: chrony
   
   timesync_ntp_servers:
     - hostname: classroom.example.com
       iburst: yes

Insert a task to set the time zone for each host. Ensure that the task uses the timezone module and executes after the rhel-system-roles.timesync role.

Because hosts may not belong to the same time zone, use a variable (host_timezone) for the time zone name.

1. Review the Examples section of the timezone module documentation.

   [student@workstation tools-automating]$ ansible-doc timezone | grep -A 4 "EXAMPLES"
   EXAMPLES:
   - name: set timezone to Asia/Tokyo
     timezone:
       name: Asia/Tokyo

2. Add a task to the post_tasks section of the play in the configure_time.yml playbook. Model the task after the documentation example, but use the host_timezone variable for the time zone name.

   The documentation in ansible-doc timezone recommends a restart of the Cron service if the module changes the timezone, to make sure Cron jobs run at the right times. Add a notify keyword to the task, with an associated value of restart crond. The post_tasks section of the play should read:

     post_tasks:
       - name: Set timezone
         timezone:
           name: "{{ host_timezone }}"
         notify: restart crond

3. Add the restart crond handler to the Time Synchronization play. The complete playbook now contains:

   ---
   - name: Time Synchronization
     hosts: database_servers
   
     roles:
       - rhel-system-roles.timesync
   
     post_tasks:
       - name: Set timezone
         timezone:
           name: "{{ host_timezone }}"
         notify: restart crond
   
     handlers:
       - name: restart crond
         service:
           name: crond
           state: restarted

For each data center, create a file named timezone.yml that contains an appropriate value for the host_timezone variable. Use the timedatectl list-timezones command to find the valid time zone string for each data center.

1. Create the group_vars subdirectories for the na_datacenter and europe_datacenter host groups.

   [student@workstation tools-automating]$ mkdir -pv \
   > group_vars/{na,europe}_datacenter
   mkdir: created directory 'group_vars/na_datacenter'
   mkdir: created directory 'group_vars/europe_datacenter'

2. Use the timedatectl list-timezones command to determine the time zone for both the US and European data centers:

   [student@workstation tools-automating]$ timedatectl list-timezones | grep Chicago
   America/Chicago
   [student@workstation tools-automating]$ timedatectl list-timezones | grep Helsinki
   Europe/Helsinki

3. Create the timezone.yml for both data centers:

   [student@workstation tools-automating]$ echo "host_timezone: America/Chicago" > \
   > group_vars/na_datacenter/timezone.yml
   [student@workstation tools-automating]$ echo "host_timezone: Europe/Helsinki" > \
   > group_vars/europe_datacenter/timezone.yml

4. The final file structure of the ~/tools-automating folder should look similar to the following tree command output:

   [student@workstation tools-automating]$ tree ~/tools-automating
   /home/student/tools-automating/
   ├── ansible.cfg
   ├── configure_time.yml
   ├── group_vars
   │   ├── all
   │   │   └── timesync.yml
   │   ├── europe_datacenter
   │   │   └── timezone.yml
   │   └── na_datacenter
   │       └── timezone.yml
   ├── inventory
   └── roles
       └── requirements.yml
   
   5 directories, 7 files

Run the playbook. Some tasks will result in errors, because they attempt to stop services that are not running in this exercise. The timesync system role would typically expect to find and stop the deprecated NTP services.

[student@workstation tools-automating]$ ansible-playbook configure_time.yml

PLAY [Time Synchronization] **************************************************

TASK [Gathering Facts] *******************************************************
ok: [serverb.lab.example.com]
ok: [servera.lab.example.com]

TASK [rhel-system-roles.timesync : Check if only NTP is needed] **************
ok: [servera.lab.example.com]
ok: [serverb.lab.example.com]

...output omitted...

TASK [rhel-system-roles.timesync : Enable timemaster] ************************
skipping: [servera.lab.example.com]
skipping: [serverb.lab.example.com]

RUNNING HANDLER [rhel-system-roles.timesync : restart chronyd] ***************
changed: [servera.lab.example.com]
changed: [serverb.lab.example.com]

TASK [Set timezone] **********************************************************
changed: [serverb.lab.example.com]
changed: [servera.lab.example.com]

RUNNING HANDLER [restart crond] **********************************************
changed: [serverb.lab.example.com]
changed: [servera.lab.example.com]

PLAY RECAP *******************************************************************
servera.lab.example.com    : ok=17   changed=6    unreachable=0    failed=0
serverb.lab.example.com    : ok=17   changed=6    unreachable=0    failed=0

Verify the time zone settings of each server. Use the Ansible command module to see the output of the timedatectl command on all the database servers.

[student@workstation tools-automating]$ ansible database_servers -m command -a timedatectl
serverb.lab.example.com | CHANGED | rc=0 >>
               Local time: Thu 2019-06-13 05:10:57 EEST
           Universal time: Thu 2019-06-13 02:10:57 UTC
                 RTC time: Thu 2019-06-13 02:10:56
                Time zone: Europe/Helsinki (EEST, +0300)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

servera.lab.example.com | CHANGED | rc=0 >>
               Local time: Wed 2019-06-12 21:10:57 CDT
           Universal time: Thu 2019-06-13 02:10:57 UTC
                 RTC time: Thu 2019-06-13 02:10:56
                Time zone: America/Chicago (CDT, -0500)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

Each server has a time zone setting based on its geographic location.