Managing the Boot Process #
No modules for managing boot process.
file module
- manage the systemd boot targets
lineinfile module
- manage the GRUB configuration.
reboot module
- enables you to reboot a host and pick up after the reboot at the exact same location.
Managing Systemd Targets #
To manage the default systemd target:
- /etc/systemd/system/default.target file must exist as a symbolic link to the desired default target.
ls -l /etc/systemd/system/default.target
lrwxrwxrwx. 1 root root 37 Mar 23 05:33 /etc/systemd/system/default.target -> /lib/systemd/system/multi-user.target
---
- name: set default boot target
hosts: ansible2
tasks:
- name: set boot target to graphical
file:
src: /usr/lib/systemd/system/graphical.target
dest: /etc/systemd/system/default.target
state: link
Rebooting Managed Hosts #
reboot module.
- Restart managed nodes.
test_command argument
- Verify the renewed availability of the managed hosts
- Specifies an arbitrary command that Ansible should run successfully on the managed hosts after the reboot. The success of this command indicates that the rebooted host is available again.
Equally useful while using the reboot module are the arguments that relate to timeouts. The reboot module uses no fewer than four of them:
• connect_timeout: The maximum seconds to wait for a successful connection before trying again
• post_reboot_delay: The number of seconds to wait after the reboot command before trying to validate the managed host is available again
• pre_reboot_delay: The number of seconds to wait before actually issuing the reboot
• reboot_timeout: The maximum seconds to wait for the rebooted machine to respond to the test command
When the rebooted host is back, the current playbook continues its tasks. This scenario is shown in the example in Listing 14-7, where first all managed hosts are rebooted, and after a successful reboot is issued, the message “successfully rebooted” is shown. Listing 14-8 shows the result of running this playbook. In Exercise 14-2 you can practice rebooting hosts using the reboot module.
Listing 14-7 Rebooting Managed Hosts
::: pre_1 — - name: reboot all hosts hosts: all gather_facts: no tasks: - name: reboot hosts reboot: msg: reboot initiated by Ansible test_command: whoami - name: print message to show host is back debug: msg: successfully rebooted :::
Listing 14-8 Verifying the Success of the reboot Module
::: pre_1 [ansible@control rhce8-book]$ ansible-playbook listing147.yaml
PLAY [reboot all hosts] *************************************************************************************************
TASK [reboot hosts] *****************************************************************************************************
changed: [ansible2]
changed: [ansible1]
changed: [ansible3]
changed: [ansible4]
changed: [ansible5]
TASK [print message to show host is back] *******************************************************************************
ok: [ansible1] => {
"msg": "successfully rebooted"
}
ok: [ansible2] => {
"msg": "successfully rebooted"
}
ok: [ansible3] => {
"msg": "successfully rebooted"
}
ok: [ansible4] => {
"msg": "successfully rebooted"
}
ok: [ansible5] => {
"msg": "successfully rebooted"
}
PLAY RECAP **************************************************************************************************************
ansible1 : ok=2 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
ansible2 : ok=2 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
ansible3 : ok=2 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
ansible4 : ok=2 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
ansible5 : ok=2 changed=1 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
:::
::: box Exercise 14-2 Managing Boot State
1. As a preparation for this playbook, so that it actually changes the default boot target on the managed host, use ansible ansible2 -m file -a “state=link src=/usr/lib/systemd/system/graphical.target dest=/etc/systemd/system/default.target”.
2. Use your editor to create the file exercise142.yaml and write the following playbook header:
---
- name: set default boot target and reboot
hosts: ansible2
tasks:
3. Now you set the default boot target to multi-user.target. Add the following task to do so:
- name: set default boot target
file:
src: /usr/lib/systemd/system/multi-user.target
dest: /etc/systemd/system/default.target
state: link
4. Complete the playbook to reboot the managed hosts by including the following tasks:
- name: reboot hosts
reboot:
msg: reboot initiated by Ansible
test_command: whoami
- name: print message to show host is back
debug:
msg: successfully rebooted
5. Run the playbook by using ansible-playbook exercise142.yaml.
6. Test that the reboot was issued successfully by using ansible ansible2 -a “systemctl get-default”. :::
Lab: Managing the Boot Process and Services #
The advanced exercise, 14-3, is a relatively easy task this time. You are guided through the procedure of creating a playbook that runs a command before the reboot, schedules a cron job at the next reboot, and, using that cron job, ensures that after rebooting a specific command is used as well. To make sure you see what happens when, you work with a temporary file to which lines are added.
::: box Exercise 14-3 Managing the Boot Process and Services
1. Use your editor to create the file exercise143.yaml and write the playbook header as follows:
---
- name: exercise143
hosts: ansible2
tasks:
2. Write the first task. This task is not really functional but enables you to check what is happening in the remaining tasks in the playbook. In this task, you use the lineinfile module to add a line to the end of the check file /tmp/rebooted. Notice how the time, including a second indicator, is written using two Ansible facts. It’s required to operate this way because not one single fact has the time in an hh:mm:ss format. Write this task code as follows:
- name: add a line to file before rebooting
lineinfile:
create: true
state: present
path: /tmp/rebooted
insertafter: EOF
line: rebooted at {{ ansible_facts[’date_time’][’time’] }}:{{ ansible_facts[’date_time’][’second’] }}
3. At this point, you can add a cron job that runs at reboot. The job that runs will add a message to the /tmp/rebooted file, and to make sure that it is working correctly, you use bash shell command substitution to print the results of the Linux date command. Notice that this is possible in the cron module because commands are executed by a bash shell, but it’s not possible in the previous task that uses the lineinfile module because in that task the commands are not processed by a shell. Now add the task as follows:
- name: run a cron job on reboot
cron:
name: "run on reboot"
state: present
special_time: reboot
job: "echo rebooted at $(date) >> /tmp/rebooted"
4. Add another task that uses the reboot module to reboot the managed host:
- name: reboot managed host
reboot:
msg: reboot initiated by Ansible
test_command: whoami
- name: show reboot success
debug:
msg: just rebooted successfully
5. Now that the playbook is complete, you can run it by using ansible-playbook exercise143.yaml. Notice that it needs a minute because it has to wait until the target host is back. When it is back, use ansible ansible2 -a “cat /tmp/rebooted”. You then see that both reboot messages are written, and there is about 30 seconds between the pre-reboot and the post-reboot commands. :::
Lab 14-1 #
Write a playbook according to the following specifications:
• The cron module must be used to restart your managed servers at 2 a.m. each weekday.
• After rebooting, a message must be written to syslog, with the text “CRON initiated reboot just completed.”
• The default systemd target must be set to multi-user.target.
• The last task should use service facts to show the current version of the cron process.